Publish Stable

- @vercel/build-utils@5.0.0
 - vercel@26.0.0
 - @vercel/client@12.0.4
 - @vercel/fs-detectors@1.0.0
 - @vercel/go@2.0.4
 - @vercel/next@3.1.3
 - @vercel/node@2.4.0
 - @vercel/python@3.0.4
 - @vercel/redwood@1.0.5
 - @vercel/remix@1.0.5
 - @vercel/ruby@1.3.12
 - @vercel/static-build@1.0.4

.prettierignore

@@ -0,0 +1,4 @@
+# https://prettier.io/docs/en/ignore.html
+
+# ignore this file with an intentional syntax error
+packages/cli/test/dev/fixtures/edge-function-error/api/edge-error-syntax.js

examples/create-react-app/src/vitals.js

@@ -24,7 +24,6 @@ export function sendToVercelAnalytics(metric) {
     speed: getConnectionSpeed(),
   };
 
-  console.log({ body });
   const blob = new Blob([new URLSearchParams(body).toString()], {
     // This content type is necessary for `sendBeacon`
     type: 'application/x-www-form-urlencoded',

package.json

@@ -31,7 +31,7 @@
     "prettier": "2.6.2",
     "ts-eager": "2.0.2",
     "ts-jest": "28.0.5",
-    "turbo": "1.2.14"
+    "turbo": "1.3.1"
   },
   "scripts": {
     "lerna": "lerna",

packages/build-utils/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@vercel/build-utils",
-  "version": "4.1.1-canary.1",
+  "version": "5.0.0",
   "license": "MIT",
   "main": "./dist/index.js",
   "types": "./dist/index.d.js",
@@ -31,7 +31,6 @@
     "@types/node-fetch": "^2.1.6",
     "@types/semver": "6.0.0",
     "@types/yazl": "2.4.2",
-    "@vercel/frameworks": "1.0.2-canary.0",
     "@vercel/ncc": "0.24.0",
     "aggregate-error": "3.0.1",
     "async-retry": "1.2.3",

packages/build-utils/src/fs/run-user-scripts.ts

@@ -61,6 +61,13 @@ export interface SpawnOptionsExtended extends SpawnOptions {
    * Pretty formatted command that is being spawned for logging purposes.
    */
   prettyCommand?: string;
+
+  /**
+   * Returns instead of throwing an error when the process exits with a
+   * non-0 exit code. When relevant, the returned object will include
+   * the error code, stdout and stderr.
+   */
+  ignoreNon0Exit?: boolean;
 }
 
 export function spawnAsync(
@@ -79,7 +86,7 @@ export function spawnAsync(
 
     child.on('error', reject);
     child.on('close', (code, signal) => {
-      if (code === 0) {
+      if (code === 0 || opts.ignoreNon0Exit) {
         return resolve();
       }
 
@@ -123,24 +130,24 @@ export function execAsync(
 
       child.on('error', reject);
       child.on('close', (code, signal) => {
-        if (code !== 0) {
-          const cmd = opts.prettyCommand
-            ? `Command "${opts.prettyCommand}"`
-            : 'Command';
-
-          return reject(
-            new NowBuildError({
-              code: `BUILD_UTILS_EXEC_${code || signal}`,
-              message: `${cmd} exited with ${code || signal}`,
-            })
-          );
+        if (code === 0 || opts.ignoreNon0Exit) {
+          return resolve({
+            code,
+            stdout: Buffer.concat(stdoutList).toString(),
+            stderr: Buffer.concat(stderrList).toString(),
+          });
         }
 
-        return resolve({
-          code,
-          stdout: Buffer.concat(stdoutList).toString(),
-          stderr: Buffer.concat(stderrList).toString(),
-        });
+        const cmd = opts.prettyCommand
+          ? `Command "${opts.prettyCommand}"`
+          : 'Command';
+
+        return reject(
+          new NowBuildError({
+            code: `BUILD_UTILS_EXEC_${code || signal}`,
+            message: `${cmd} exited with ${code || signal}`,
+          })
+        );
       });
     }
   );
@@ -166,9 +173,30 @@ export async function execCommand(command: string, options: SpawnOptions = {}) {
   return true;
 }
 
-export async function getNodeBinPath({ cwd }: { cwd: string }) {
-  const { stdout } = await execAsync('npm', ['bin'], { cwd });
-  return stdout.trim();
+export async function getNodeBinPath({
+  cwd,
+}: {
+  cwd: string;
+}): Promise<string> {
+  const { code, stdout, stderr } = await execAsync('npm', ['bin'], {
+    cwd,
+    prettyCommand: 'npm bin',
+
+    // in some rare cases, we saw `npm bin` exit with a non-0 code, but still
+    // output the right bin path, so we ignore the exit code
+    ignoreNon0Exit: true,
+  });
+
+  const nodeBinPath = stdout.trim();
+
+  if (path.isAbsolute(nodeBinPath)) {
+    return nodeBinPath;
+  }
+
+  throw new NowBuildError({
+    code: `BUILD_UTILS_GET_NODE_BIN_PATH`,
+    message: `Running \`npm bin\` failed to return a valid bin path (code=${code}, stdout=${stdout}, stderr=${stderr})`,
+  });
 }
 
 async function chmodPlusX(fsPath: string) {
@@ -205,10 +233,23 @@ export function getSpawnOptions(
   };
 
   if (!meta.isDev) {
-    // Ensure that the selected Node version is at the beginning of the `$PATH`
-    opts.env.PATH = `/node${nodeVersion.major}/bin${path.delimiter}${
-      opts.env.PATH || process.env.PATH
-    }`;
+    let found = false;
+    const oldPath = opts.env.PATH || process.env.PATH || '';
+
+    const pathSegments = oldPath.split(path.delimiter).map(segment => {
+      if (/^\/node[0-9]+\/bin/.test(segment)) {
+        found = true;
+        return `/node${nodeVersion.major}/bin`;
+      }
+      return segment;
+    });
+
+    if (!found) {
+      // If we didn't find & replace, prepend at beginning of PATH
+      pathSegments.unshift(`/node${nodeVersion.major}/bin`);
+    }
+
+    opts.env.PATH = pathSegments.filter(Boolean).join(path.delimiter);
   }
 
   return opts;
@@ -446,20 +487,31 @@ export function getEnvForPackageManager({
   env: { [x: string]: string | undefined };
 }) {
   const newEnv: { [x: string]: string | undefined } = { ...env };
+  const oldPath = env.PATH + '';
+  const npm7 = '/node16/bin-npm7';
+  const pnpm7 = '/pnpm7/node_modules/.bin';
+  const corepackEnabled = env.ENABLE_EXPERIMENTAL_COREPACK === '1';
   if (cliType === 'npm') {
     if (
       typeof lockfileVersion === 'number' &&
       lockfileVersion >= 2 &&
-      (nodeVersion?.major || 0) < 16
+      (nodeVersion?.major || 0) < 16 &&
+      !oldPath.includes(npm7) &&
+      !corepackEnabled
     ) {
       // Ensure that npm 7 is at the beginning of the `$PATH`
-      newEnv.PATH = `/node16/bin-npm7${path.delimiter}${env.PATH}`;
-      console.log('Detected `package-lock.json` generated by npm 7...');
+      newEnv.PATH = `${npm7}${path.delimiter}${oldPath}`;
+      console.log('Detected `package-lock.json` generated by npm 7+...');
     }
   } else if (cliType === 'pnpm') {
-    if (typeof lockfileVersion === 'number' && lockfileVersion === 5.4) {
+    if (
+      typeof lockfileVersion === 'number' &&
+      lockfileVersion === 5.4 &&
+      !oldPath.includes(pnpm7) &&
+      !corepackEnabled
+    ) {
       // Ensure that pnpm 7 is at the beginning of the `$PATH`
-      newEnv.PATH = `/pnpm7/node_modules/.bin${path.delimiter}${env.PATH}`;
+      newEnv.PATH = `${pnpm7}${path.delimiter}${oldPath}`;
       console.log('Detected `pnpm-lock.yaml` generated by pnpm 7...');
     }
   } else {

packages/build-utils/src/index.ts

@@ -80,16 +80,6 @@ export {
 };
 
 export { EdgeFunction } from './edge-function';
-export {
-  detectBuilders,
-  detectOutputDirectory,
-  detectApiDirectory,
-  detectApiExtensions,
-} from './detect-builders';
-export { detectFileSystemAPI } from './detect-file-system-api';
-export { detectFramework } from './detect-framework';
-export { getProjectPaths } from './get-project-paths';
-export { DetectorFilesystem } from './detectors/filesystem';
 export { readConfigFile } from './fs/read-config-file';
 export { normalizePath } from './fs/normalize-path';
 
@@ -97,35 +87,3 @@ export * from './should-serve';
 export * from './schemas';
 export * from './types';
 export * from './errors';
-
-/**
- * Helper function to support both `@vercel` and legacy `@now` official Runtimes.
- */
-export const isOfficialRuntime = (desired: string, name?: string): boolean => {
-  if (typeof name !== 'string') {
-    return false;
-  }
-  return (
-    name === `@vercel/${desired}` ||
-    name === `@now/${desired}` ||
-    name.startsWith(`@vercel/${desired}@`) ||
-    name.startsWith(`@now/${desired}@`)
-  );
-};
-
-export const isStaticRuntime = (name?: string): boolean => {
-  return isOfficialRuntime('static', name);
-};
-
-export { workspaceManagers } from './workspaces/workspace-managers';
-export {
-  getWorkspaces,
-  GetWorkspaceOptions,
-  Workspace,
-  WorkspaceType,
-} from './workspaces/get-workspaces';
-export {
-  getWorkspacePackagePaths,
-  GetWorkspacePackagePathsOptions,
-} from './workspaces/get-workspace-package-paths';
-export { monorepoManagers } from './monorepos/monorepo-managers';

packages/build-utils/test/convert-runtime/invalid-functions/api/users.rb

@@ -1 +0,0 @@
-# users.rb

packages/build-utils/test/convert-runtime/invalid-functions/vercel.json

@@ -1,10 +0,0 @@
-{
-  "functions": {
-    "api/users.rb": {
-      "memory": 3008
-    },
-    "api/doesnt-exist.rb": {
-      "memory": 768
-    }
-  }
-}

packages/build-utils/test/convert-runtime/python-api/api/db/[id].py

@@ -1 +0,0 @@
-# [id].py

packages/build-utils/test/convert-runtime/python-api/api/index.py

@@ -1 +0,0 @@
-# index

packages/build-utils/test/convert-runtime/python-api/api/project/[aid]/[bid]/index.py

@@ -1 +0,0 @@
-# project/[aid]/[bid]/index.py

packages/build-utils/test/convert-runtime/python-api/api/users/get.py

@@ -1 +0,0 @@
-# get

packages/build-utils/test/convert-runtime/python-api/api/users/post.py

@@ -1 +0,0 @@
-# post

packages/build-utils/test/convert-runtime/python-api/file.txt

@@ -1 +0,0 @@
-This file should also be included

packages/build-utils/test/convert-runtime/python-api/util/date.py

@@ -1 +0,0 @@
-# date

packages/build-utils/test/convert-runtime/python-api/util/math.py

@@ -1 +0,0 @@
-# math

packages/build-utils/test/convert-runtime/python-api/vercel.json

@@ -1,7 +0,0 @@
-{
-  "functions": {
-    "api/users/post.py": {
-      "memory": 3008
-    }
-  }
-}

packages/build-utils/test/integration.test.ts

@@ -5,7 +5,6 @@ import {
   testDeployment,
   // @ts-ignore
 } from '../../../test/lib/deployment/test-deployment';
-import { glob, detectBuilders } from '../src';
 
 jest.setTimeout(4 * 60 * 1000);
 
@@ -32,11 +31,6 @@ const skipFixtures: string[] = [
   '08-zero-config-middleman',
   '21-npm-workspaces',
   '23-pnpm-workspaces',
-  '27-yarn-workspaces',
-  '28-turborepo-with-yarn-workspaces',
-  '29-nested-workspaces',
-  '30-double-nested-workspaces',
-  '31-turborepo-in-package-json',
 ];
 
 // eslint-disable-next-line no-restricted-syntax
@@ -83,145 +77,3 @@ for (const builder of buildersToTestWith) {
     }
   }
 }
-
-it('Test `detectBuilders` and `detectRoutes`', async () => {
-  const fixture = path.join(__dirname, 'fixtures', '01-zero-config-api');
-  const pkg = await fs.readJSON(path.join(fixture, 'package.json'));
-  const fileList = await glob('**', fixture);
-  const files = Object.keys(fileList);
-
-  const probes = [
-    {
-      path: '/api/my-endpoint',
-      mustContain: 'my-endpoint',
-      status: 200,
-    },
-    {
-      path: '/api/other-endpoint',
-      mustContain: 'other-endpoint',
-      status: 200,
-    },
-    {
-      path: '/api/team/zeit',
-      mustContain: 'team/zeit',
-      status: 200,
-    },
-    {
-      path: '/api/user/myself',
-      mustContain: 'user/myself',
-      status: 200,
-    },
-    {
-      path: '/api/not-okay/',
-      status: 404,
-    },
-    {
-      path: '/api',
-      status: 404,
-    },
-    {
-      path: '/api/',
-      status: 404,
-    },
-    {
-      path: '/',
-      mustContain: 'hello from index.txt',
-    },
-  ];
-
-  const { builders, defaultRoutes } = await detectBuilders(files, pkg);
-
-  const nowConfig = { builds: builders, routes: defaultRoutes, probes };
-
-  await fs.writeFile(
-    path.join(fixture, 'now.json'),
-    JSON.stringify(nowConfig, null, 2)
-  );
-
-  const deployment = await testDeployment(
-    { builderUrl, buildUtilsUrl },
-    fixture
-  );
-  expect(deployment).toBeDefined();
-});
-
-it('Test `detectBuilders` with `index` files', async () => {
-  const fixture = path.join(__dirname, 'fixtures', '02-zero-config-api');
-  const pkg = await fs.readJSON(path.join(fixture, 'package.json'));
-  const fileList = await glob('**', fixture);
-  const files = Object.keys(fileList);
-
-  const probes = [
-    {
-      path: '/api/not-okay',
-      status: 404,
-    },
-    {
-      path: '/api',
-      mustContain: 'hello from api/index.js',
-      status: 200,
-    },
-    {
-      path: '/api/',
-      mustContain: 'hello from api/index.js',
-      status: 200,
-    },
-    {
-      path: '/api/index',
-      mustContain: 'hello from api/index.js',
-      status: 200,
-    },
-    {
-      path: '/api/index.js',
-      mustContain: 'hello from api/index.js',
-      status: 200,
-    },
-    {
-      path: '/api/date.js',
-      mustContain: 'hello from api/date.js',
-      status: 200,
-    },
-    {
-      // Someone might expect this to be `date.js`,
-      // but I doubt that there is any case were both
-      // `date/index.js` and `date.js` exists,
-      // so it is not special cased
-      path: '/api/date',
-      mustContain: 'hello from api/date/index.js',
-      status: 200,
-    },
-    {
-      path: '/api/date/',
-      mustContain: 'hello from api/date/index.js',
-      status: 200,
-    },
-    {
-      path: '/api/date/index',
-      mustContain: 'hello from api/date/index.js',
-      status: 200,
-    },
-    {
-      path: '/api/date/index.js',
-      mustContain: 'hello from api/date/index.js',
-      status: 200,
-    },
-    {
-      path: '/',
-      mustContain: 'hello from index.txt',
-    },
-  ];
-
-  const { builders, defaultRoutes } = await detectBuilders(files, pkg);
-
-  const nowConfig = { builds: builders, routes: defaultRoutes, probes };
-  await fs.writeFile(
-    path.join(fixture, 'now.json'),
-    JSON.stringify(nowConfig, null, 2)
-  );
-
-  const deployment = await testDeployment(
-    { builderUrl, buildUtilsUrl },
-    fixture
-  );
-  expect(deployment).toBeDefined();
-});

packages/build-utils/test/unit.exec-async.test.ts

@@ -0,0 +1,29 @@
+import { execAsync, NowBuildError } from '../src';
+
+it('should execute a command', async () => {
+  const { code, stdout, stderr } = await execAsync('echo', ['hello']);
+
+  expect(code).toBe(0);
+  expect(stdout).toContain('hello');
+  expect(stderr).toBe('');
+});
+
+it('should throw if the command exits with non-0 code', async () => {
+  await expect(execAsync('find', ['unknown-file'])).rejects.toBeInstanceOf(
+    NowBuildError
+  );
+});
+
+it('should return if the command exits with non-0 code and ignoreNon0Exit=true', async () => {
+  const { code, stdout, stderr } = await execAsync('find', ['unknown-file'], {
+    ignoreNon0Exit: true,
+  });
+
+  expect(code).toBe(process.platform === 'win32' ? 2 : 1);
+  expect(stdout).toBe('');
+  expect(stderr).toContain(
+    process.platform === 'win32'
+      ? 'Parameter format not correct'
+      : 'No such file or directory'
+  );
+});

packages/build-utils/test/unit.get-env-for-package-manager.test.ts

@@ -38,6 +38,38 @@ describe('Test `getEnvForPackageManager()`', () => {
         PATH: `/node16/bin-npm7${delimiter}foo`,
       },
     },
+    {
+      name: 'should not set npm path if corepack enabled',
+      args: {
+        cliType: 'npm',
+        nodeVersion: { major: 14, range: '14.x', runtime: 'nodejs14.x' },
+        lockfileVersion: 2,
+        env: {
+          FOO: 'bar',
+          ENABLE_EXPERIMENTAL_COREPACK: '1',
+        },
+      },
+      want: {
+        FOO: 'bar',
+        ENABLE_EXPERIMENTAL_COREPACK: '1',
+      },
+    },
+    {
+      name: 'should not prepend npm path again if already detected',
+      args: {
+        cliType: 'npm',
+        nodeVersion: { major: 14, range: '14.x', runtime: 'nodejs14.x' },
+        lockfileVersion: 2,
+        env: {
+          FOO: 'bar',
+          PATH: `/node16/bin-npm7${delimiter}foo`,
+        },
+      },
+      want: {
+        FOO: 'bar',
+        PATH: `/node16/bin-npm7${delimiter}foo`,
+      },
+    },
     {
       name: 'should not set path if node is 16 and npm 7+ is detected',
       args: {
@@ -101,6 +133,38 @@ describe('Test `getEnvForPackageManager()`', () => {
         PATH: `/pnpm7/node_modules/.bin${delimiter}foo`,
       },
     },
+    {
+      name: 'should not set pnpm path if corepack is enabled',
+      args: {
+        cliType: 'pnpm',
+        nodeVersion: { major: 16, range: '16.x', runtime: 'nodejs16.x' },
+        lockfileVersion: 5.4,
+        env: {
+          FOO: 'bar',
+          ENABLE_EXPERIMENTAL_COREPACK: '1',
+        },
+      },
+      want: {
+        FOO: 'bar',
+        ENABLE_EXPERIMENTAL_COREPACK: '1',
+      },
+    },
+    {
+      name: 'should not prepend pnpm path again if already detected',
+      args: {
+        cliType: 'pnpm',
+        nodeVersion: { major: 16, range: '16.x', runtime: 'nodejs16.x' },
+        lockfileVersion: 5.4,
+        env: {
+          FOO: 'bar',
+          PATH: `/pnpm7/node_modules/.bin${delimiter}foo`,
+        },
+      },
+      want: {
+        FOO: 'bar',
+        PATH: `/pnpm7/node_modules/.bin${delimiter}foo`,
+      },
+    },
     {
       name: 'should not set path if pnpm 6 is detected',
       args: {

packages/build-utils/test/unit.get-spawn-options.test.ts

@@ -0,0 +1,111 @@
+import { delimiter } from 'path';
+import { getSpawnOptions } from '../src';
+
+describe('Test `getSpawnOptions()`', () => {
+  const origProcessEnvPath = process.env.PATH;
+
+  beforeEach(() => {
+    process.env.PATH = undefined;
+  });
+
+  afterEach(() => {
+    process.env.PATH = origProcessEnvPath;
+  });
+
+  const cases: Array<{
+    name: string;
+    args: Parameters<typeof getSpawnOptions>;
+    envPath: string | undefined;
+    want: string | undefined;
+  }> = [
+    {
+      name: 'should do nothing when isDev and node14',
+      args: [
+        { isDev: true },
+        { major: 14, range: '14.x', runtime: 'nodejs14.x' },
+      ],
+      envPath: '/foo',
+      want: '/foo',
+    },
+    {
+      name: 'should do nothing when isDev and node16',
+      args: [
+        { isDev: true },
+        { major: 16, range: '16.x', runtime: 'nodejs16.x' },
+      ],
+      envPath: '/foo',
+      want: '/foo',
+    },
+    {
+      name: 'should replace 14 with 16 when only path',
+      args: [
+        { isDev: false },
+        { major: 16, range: '16.x', runtime: 'nodejs16.x' },
+      ],
+      envPath: '/node14/bin',
+      want: '/node16/bin',
+    },
+    {
+      name: 'should replace 14 with 16 at beginning',
+      args: [
+        { isDev: false },
+        { major: 16, range: '16.x', runtime: 'nodejs16.x' },
+      ],
+      envPath: `/node14/bin${delimiter}/foo`,
+      want: `/node16/bin${delimiter}/foo`,
+    },
+    {
+      name: 'should replace 14 with 16 at end',
+      args: [
+        { isDev: false },
+        { major: 16, range: '16.x', runtime: 'nodejs16.x' },
+      ],
+      envPath: `/foo${delimiter}/node14/bin`,
+      want: `/foo${delimiter}/node16/bin`,
+    },
+    {
+      name: 'should replace 14 with 16 in middle',
+      args: [
+        { isDev: false },
+        { major: 16, range: '16.x', runtime: 'nodejs16.x' },
+      ],
+      envPath: `/foo${delimiter}/node14/bin${delimiter}/bar`,
+      want: `/foo${delimiter}/node16/bin${delimiter}/bar`,
+    },
+    {
+      name: 'should prepend 16 at beginning when nothing to replace',
+      args: [
+        { isDev: false },
+        { major: 16, range: '16.x', runtime: 'nodejs16.x' },
+      ],
+      envPath: `/foo`,
+      want: `/node16/bin${delimiter}/foo`,
+    },
+    {
+      name: 'should prepend 16 at beginning no path input',
+      args: [
+        { isDev: false },
+        { major: 16, range: '16.x', runtime: 'nodejs16.x' },
+      ],
+      envPath: '',
+      want: `/node16/bin`,
+    },
+    {
+      name: 'should replace 12 with 14 when only path',
+      args: [
+        { isDev: false },
+        { major: 14, range: '14.x', runtime: 'nodejs14.x' },
+      ],
+      envPath: '/node12/bin',
+      want: '/node14/bin',
+    },
+  ];
+
+  for (const { name, args, envPath, want } of cases) {
+    it(name, () => {
+      process.env.PATH = envPath;
+      const opts = getSpawnOptions(...args);
+      expect(opts.env?.PATH).toBe(want);
+    });
+  }
+});

packages/build-utils/test/unit.spawn-async.test.ts

@@ -0,0 +1,21 @@
+import { spawnAsync, NowBuildError } from '../src';
+
+it('should execute a command', async () => {
+  // should resolve (it doesn't return anything, so it resolves with "undefined")
+  await expect(spawnAsync('echo', ['hello'])).resolves.toBeUndefined();
+});
+
+it('should throw if the command exits with non-0 code', async () => {
+  await expect(spawnAsync('find', ['unknown-file'])).rejects.toBeInstanceOf(
+    NowBuildError
+  );
+});
+
+it('should return if the command exits with non-0 code and ignoreNon0Exit=true', async () => {
+  // should resolve (it doesn't return anything, so it resolves with "undefined")
+  await expect(
+    spawnAsync('find', ['unknown-file'], {
+      ignoreNon0Exit: true,
+    })
+  ).resolves.toBeUndefined();
+});

packages/build-utils/test/unit.test.ts

@@ -18,6 +18,8 @@ import {
   Meta,
 } from '../src';
 
+jest.setTimeout(7 * 1000);
+
 async function expectBuilderError(promise: Promise<any>, pattern: string) {
   let result;
   try {

packages/cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "vercel",
-  "version": "25.1.1-canary.9",
+  "version": "26.0.0",
   "preferGlobal": true,
   "license": "Apache-2.0",
   "description": "The command-line interface for Vercel",
@@ -42,15 +42,15 @@
     "node": ">= 14"
   },
   "dependencies": {
-    "@vercel/build-utils": "4.1.1-canary.1",
-    "@vercel/go": "2.0.2-canary.1",
-    "@vercel/next": "3.0.4",
-    "@vercel/node": "2.2.1-canary.1",
-    "@vercel/python": "3.0.2-canary.1",
-    "@vercel/redwood": "1.0.2-canary.1",
-    "@vercel/remix": "1.0.2-canary.1",
-    "@vercel/ruby": "1.3.10-canary.1",
-    "@vercel/static-build": "1.0.2-canary.1",
+    "@vercel/build-utils": "5.0.0",
+    "@vercel/go": "2.0.4",
+    "@vercel/next": "3.1.3",
+    "@vercel/node": "2.4.0",
+    "@vercel/python": "3.0.4",
+    "@vercel/redwood": "1.0.5",
+    "@vercel/remix": "1.0.5",
+    "@vercel/ruby": "1.3.12",
+    "@vercel/static-build": "1.0.4",
     "update-notifier": "5.1.0"
   },
   "devDependencies": {
@@ -95,8 +95,9 @@
     "@types/which": "1.3.2",
     "@types/write-json-file": "2.2.1",
     "@types/yauzl-promise": "2.1.0",
-    "@vercel/client": "12.0.2-canary.1",
-    "@vercel/frameworks": "1.0.2-canary.0",
+    "@vercel/client": "12.0.4",
+    "@vercel/frameworks": "1.0.2",
+    "@vercel/fs-detectors": "1.0.0",
     "@vercel/ncc": "0.24.0",
     "@zeit/fun": "0.11.2",
     "@zeit/source-map-support": "0.6.2",

packages/cli/src/commands/alias/rm.ts

@@ -10,7 +10,6 @@ import confirm from '../../util/input/confirm';
 import findAliasByAliasOrId from '../../util/alias/find-alias-by-alias-or-id';
 
 import { Alias } from '../../types';
-import { Output } from '../../util/output';
 import { isValidName } from '../../util/is-valid-name';
 import { getCommandName } from '../../util/pkg-name';
 
@@ -71,7 +70,7 @@ export default async function rm(
   }
 
   const removeStamp = stamp();
-  if (!opts['--yes'] && !(await confirmAliasRemove(output, alias))) {
+  if (!opts['--yes'] && !(await confirmAliasRemove(client, alias))) {
     output.log('Aborted');
     return 0;
   }
@@ -85,7 +84,7 @@ export default async function rm(
   return 0;
 }
 
-async function confirmAliasRemove(output: Output, alias: Alias) {
+async function confirmAliasRemove(client: Client, alias: Alias) {
   const srcUrl = alias.deployment
     ? chalk.underline(alias.deployment.url)
     : null;
@@ -104,7 +103,7 @@ async function confirmAliasRemove(output: Output, alias: Alias) {
     }
   );
 
-  output.log(`The following alias will be removed permanently`);
-  output.print(`  ${tbl}\n`);
-  return confirm(chalk.red('Are you sure?'), false);
+  client.output.log(`The following alias will be removed permanently`);
+  client.output.print(`  ${tbl}\n`);
+  return confirm(client, chalk.red('Are you sure?'), false);
 }

packages/cli/src/commands/billing/add.js

@@ -127,7 +127,7 @@ export default async function ({ creditCards, clear = false, contextName }) {
     }
 
     console.log(''); // New line
-    const stopSpinner = wait('Saving card');
+    const stopSpinner = wait(process.stderr, 'Saving card');
 
     try {
       const res = await creditCards.add({

packages/cli/src/commands/billing/index.js

@@ -174,7 +174,7 @@ export default async client => {
         )} ${chalk.gray(`[${elapsed}]`)}`;
         const choices = buildInquirerChoices(cards);
 
-        cardId = await listInput({
+        cardId = await listInput(client, {
           message,
           choices,
           separator: true,
@@ -187,6 +187,7 @@ export default async client => {
       if (cardId) {
         const label = `Are you sure that you to set this card as the default?`;
         const confirmation = await promptBool(label, {
+          ...client,
           trailing: '\n',
         });
 
@@ -250,7 +251,7 @@ export default async client => {
         )} under ${chalk.bold(contextName)} ${chalk.gray(`[${elapsed}]`)}`;
         const choices = buildInquirerChoices(cards);
 
-        cardId = await listInput({
+        cardId = await listInput(client, {
           message,
           choices,
           separator: true,
@@ -262,7 +263,7 @@ export default async client => {
       // typed `vercel billing rm <some-id>`) is valid
       if (cardId) {
         const label = `Are you sure that you want to remove this card?`;
-        const confirmation = await promptBool(label);
+        const confirmation = await promptBool(label, client);
         if (!confirmation) {
           console.log('Aborted');
           break;

packages/cli/src/commands/bisect/index.ts

@@ -14,8 +14,8 @@ import logo from '../../util/output/logo';
 import getArgs from '../../util/get-args';
 import Client from '../../util/client';
 import { getPkgName } from '../../util/pkg-name';
-import { Output } from '../../util/output';
 import { Deployment, PaginationOptions } from '../../types';
+import { normalizeURL } from '../../util/bisect/normalize-url';
 
 interface DeploymentV6
   extends Pick<
@@ -85,10 +85,10 @@ export default async function main(client: Client): Promise<number> {
 
   let bad =
     argv['--bad'] ||
-    (await prompt(output, `Specify a URL where the bug occurs:`));
+    (await prompt(client, `Specify a URL where the bug occurs:`));
   let good =
     argv['--good'] ||
-    (await prompt(output, `Specify a URL where the bug does not occur:`));
+    (await prompt(client, `Specify a URL where the bug does not occur:`));
   let subpath = argv['--path'] || '';
   let run = argv['--run'] || '';
   const openEnabled = argv['--open'] || false;
@@ -97,9 +97,7 @@ export default async function main(client: Client): Promise<number> {
     run = resolve(run);
   }
 
-  if (!bad.startsWith('https://')) {
-    bad = `https://${bad}`;
-  }
+  bad = normalizeURL(bad);
   let parsed = parse(bad);
   if (!parsed.hostname) {
     output.error('Invalid input: no hostname provided');
@@ -120,9 +118,7 @@ export default async function main(client: Client): Promise<number> {
 
   const badDeploymentPromise = getDeployment(client, bad).catch(err => err);
 
-  if (!good.startsWith('https://')) {
-    good = `https://${good}`;
-  }
+  good = normalizeURL(good);
   parsed = parse(good);
   if (!parsed.hostname) {
     output.error('Invalid input: no hostname provided');
@@ -146,7 +142,7 @@ export default async function main(client: Client): Promise<number> {
 
   if (!subpath) {
     subpath = await prompt(
-      output,
+      client,
       `Specify the URL subpath where the bug occurs:`
     );
   }
@@ -394,10 +390,10 @@ function getCommit(deployment: DeploymentV6) {
   return { sha, message };
 }
 
-async function prompt(output: Output, message: string): Promise<string> {
+async function prompt(client: Client, message: string): Promise<string> {
   // eslint-disable-next-line no-constant-condition
   while (true) {
-    const { val } = await inquirer.prompt({
+    const { val } = await client.prompt({
       type: 'input',
       name: 'val',
       message,
@@ -405,7 +401,7 @@ async function prompt(output: Output, message: string): Promise<string> {
     if (val) {
       return val;
     } else {
-      output.error('A value must be specified');
+      client.output.error('A value must be specified');
     }
   }
 }

packages/cli/src/commands/build.ts

@@ -3,7 +3,6 @@ import chalk from 'chalk';
 import dotenv from 'dotenv';
 import { join, normalize, relative, resolve } from 'path';
 import {
-  detectBuilders,
   normalizePath,
   Files,
   FileFsRef,
@@ -17,6 +16,7 @@ import {
   BuildResultV3,
   NowBuildError,
 } from '@vercel/build-utils';
+import { detectBuilders } from '@vercel/fs-detectors';
 import minimatch from 'minimatch';
 import {
   appendRoutesToPhase,
@@ -140,6 +140,7 @@ export default async function main(client: Client): Promise<number> {
       }
 
       confirmed = await confirm(
+        client,
         `No Project Settings found locally. Run ${cli.getCommandName(
           'pull'
         )} for retrieving them?`,

packages/cli/src/commands/deploy/index.ts

@@ -160,12 +160,12 @@ export default async (client: Client) => {
     }
   }
 
-  const { log, debug, error, prettyError, isTTY } = output;
+  const { log, debug, error, prettyError } = output;
 
-  const quiet = !isTTY;
+  const quiet = !client.stdout.isTTY;
 
   // check paths
-  const pathValidation = await validatePaths(output, paths);
+  const pathValidation = await validatePaths(client, paths);
 
   if (!pathValidation.valid) {
     return pathValidation.exitCode;
@@ -243,6 +243,7 @@ export default async (client: Client) => {
     const shouldStartSetup =
       autoConfirm ||
       (await confirm(
+        client,
         `Set up and deploy ${chalk.cyan(`“${toHumanPath(path)}”`)}?`,
         true
       ));
@@ -287,7 +288,7 @@ export default async (client: Client) => {
 
     if (typeof projectOrNewProjectName === 'string') {
       newProjectName = projectOrNewProjectName;
-      rootDirectory = await inputRootDirectory(path, output, autoConfirm);
+      rootDirectory = await inputRootDirectory(client, path, autoConfirm);
     } else {
       project = projectOrNewProjectName;
       rootDirectory = project.rootDirectory;
@@ -521,7 +522,7 @@ export default async (client: Client) => {
       }
 
       const settings = await editProjectSettings(
-        output,
+        client,
         projectSettings,
         framework,
         false,

packages/cli/src/commands/dns/add.ts

@@ -46,7 +46,7 @@ export default async function add(
 
   const addStamp = stamp();
   const { domain, data: argData } = parsedParams;
-  const data = await getDNSData(output, argData);
+  const data = await getDNSData(client, argData);
   if (!data) {
     output.log(`Aborted`);
     return 1;

packages/cli/src/commands/domains/buy.ts

@@ -87,7 +87,8 @@ export default async function buy(
     !(await promptBool(
       `Buy now for ${chalk.bold(`$${price}`)} (${`${period}yr${
         period > 1 ? 's' : ''
-      }`})?`
+      }`})?`,
+      client
     ))
   ) {
     return 0;
@@ -99,7 +100,7 @@ export default async function buy(
       : `Auto renew every ${renewalPrice.period} years for ${chalk.bold(
           `$${price}`
         )}?`,
-    { defaultValue: true }
+    { ...client, defaultValue: true }
   );
 
   let buyResult;

packages/cli/src/commands/domains/move.ts

@@ -77,7 +77,8 @@ export default async function move(
       !(await promptBool(
         `Are you sure you want to move ${param(domainName)} to ${param(
           destination
-        )}?`
+        )}?`,
+        client
       ))
     ) {
       output.log('Aborted');
@@ -95,7 +96,8 @@ export default async function move(
       );
       if (
         !(await promptBool(
-          `Are you sure you want to move ${param(domainName)}?`
+          `Are you sure you want to move ${param(domainName)}?`,
+          client
         ))
       ) {
         output.log('Aborted');

packages/cli/src/commands/domains/rm.ts

@@ -92,7 +92,10 @@ export default async function rm(
   const skipConfirmation = opts['--yes'] || false;
   if (
     !skipConfirmation &&
-    !(await promptBool(`Are you sure you want to remove ${param(domainName)}?`))
+    !(await promptBool(
+      `Are you sure you want to remove ${param(domainName)}?`,
+      client
+    ))
   ) {
     output.log('Aborted');
     return 0;
@@ -230,7 +233,7 @@ async function removeDomain(
 
     if (
       !skipConfirmation &&
-      !(await promptBool(`Remove conflicts associated with domain?`))
+      !(await promptBool(`Remove conflicts associated with domain?`, client))
     ) {
       output.log('Aborted');
       return 0;

packages/cli/src/commands/domains/transfer-in.ts

@@ -81,7 +81,8 @@ export default async function transferIn(
   const shouldTransfer = await promptBool(
     transferPolicy === 'no-change'
       ? `Transfer now for ${chalk.bold(`$${price}`)}?`
-      : `Transfer now with 1yr renewal for ${chalk.bold(`$${price}`)}?`
+      : `Transfer now with 1yr renewal for ${chalk.bold(`$${price}`)}?`,
+    client
   );
   if (!shouldTransfer) {
     return 0;

packages/cli/src/commands/env/add.ts

@@ -31,7 +31,7 @@ export default async function add(
   // improve the way we show inquirer prompts
   require('../../util/input/patch-inquirer');
 
-  const stdInput = await readStandardInput();
+  const stdInput = await readStandardInput(client.stdin);
   let [envName, envTargetArg, envGitBranch] = args;
 
   if (args.length > 3) {

packages/cli/src/commands/env/pull.ts

@@ -74,6 +74,7 @@ export default async function pull(
     exists &&
     !skipConfirmation &&
     !(await confirm(
+      client,
       `Found existing file ${param(filename)}. Do you want to overwrite?`,
       false
     ))

packages/cli/src/commands/env/rm.ts

@@ -104,6 +104,7 @@ export default async function rm(
   if (
     !skipConfirmation &&
     !(await confirm(
+      client,
       `Removing Environment Variable ${param(env.key)} from ${formatEnvTarget(
         env
       )} in Project ${chalk.bold(project.name)}. Are you sure?`,

packages/cli/src/commands/init/init.ts

@@ -46,7 +46,11 @@ export default async function init(
   const exampleList = examples.filter(x => x.visible).map(x => x.name);
 
   if (!name) {
-    const chosen = await chooseFromDropdown('Select example:', exampleList);
+    const chosen = await chooseFromDropdown(
+      client,
+      'Select example:',
+      exampleList
+    );
 
     if (!chosen) {
       output.log('Aborted');
@@ -65,7 +69,7 @@ export default async function init(
     return extractExample(client, name, dir, force, 'v1');
   }
 
-  const found = await guess(exampleList, name);
+  const found = await guess(client, exampleList, name);
 
   if (typeof found === 'string') {
     return extractExample(client, found, dir, force);
@@ -90,14 +94,18 @@ async function fetchExampleList(client: Client) {
 /**
  * Prompt user for choosing which example to init
  */
-async function chooseFromDropdown(message: string, exampleList: string[]) {
+async function chooseFromDropdown(
+  client: Client,
+  message: string,
+  exampleList: string[]
+) {
   const choices = exampleList.map(name => ({
     name,
     value: name,
     short: name,
   }));
 
-  return listInput({
+  return listInput(client, {
     message,
     choices,
   });
@@ -194,7 +202,7 @@ function prepareFolder(cwd: string, folder: string, force?: boolean) {
 /**
  * Guess which example user try to init
  */
-async function guess(exampleList: string[], name: string) {
+async function guess(client: Client, exampleList: string[], name: string) {
   const GuessError = new Error(
     `No example found for ${chalk.bold(name)}, run ${getCommandName(
       `init`
@@ -208,7 +216,7 @@ async function guess(exampleList: string[], name: string) {
   const found = didYouMean(name, exampleList, 0.7);
 
   if (typeof found === 'string') {
-    if (await promptBool(`Did you mean ${chalk.bold(found)}?`)) {
+    if (await promptBool(`Did you mean ${chalk.bold(found)}?`, client)) {
       return found;
     }
   } else {

packages/cli/src/commands/teams/switch.ts

@@ -83,7 +83,7 @@ export default async function main(client: Client, desiredSlug?: string) {
     ];
 
     output.stopSpinner();
-    desiredSlug = await listInput({
+    desiredSlug = await listInput(client, {
       message: 'Switch to:',
       choices,
       eraseFinalAnswer: true,

packages/cli/src/commands/whoami.ts

@@ -54,12 +54,12 @@ export default async (client: Client): Promise<number> => {
     throw err;
   }
 
-  if (output.isTTY) {
+  if (client.stdout.isTTY) {
     output.log(contextName);
   } else {
     // If stdout is not a TTY, then only print the username
     // to support piping the output to another file / exe
-    output.print(`${contextName}\n`, { w: process.stdout });
+    client.stdout.write(`${contextName}\n`);
   }
 
   return 0;

packages/cli/src/index.ts

@@ -23,7 +23,7 @@ import * as Sentry from '@sentry/node';
 import hp from './util/humanize-path';
 import commands from './commands';
 import pkg from './util/pkg';
-import createOutput from './util/output';
+import { Output } from './util/output';
 import cmd from './util/output/cmd';
 import info from './util/output/info';
 import error from './util/output/error';
@@ -109,7 +109,7 @@ const main = async () => {
   }
 
   const isDebugging = argv['--debug'];
-  const output = createOutput({ debug: isDebugging });
+  const output = new Output(process.stderr, { debug: isDebugging });
 
   debug = output.debug;
 
@@ -387,6 +387,9 @@ const main = async () => {
   // Shared API `Client` instance for all sub-commands to utilize
   client = new Client({
     apiUrl,
+    stdin: process.stdin,
+    stdout: process.stdout,
+    stderr: output.stream,
     output,
     config,
     authConfig,
@@ -796,7 +799,5 @@ process.on('uncaughtException', handleUnexpected);
 main()
   .then(exitCode => {
     process.exitCode = exitCode;
-    // @ts-ignore - "nowExit" is a non-standard event name
-    process.emit('nowExit');
   })
   .catch(handleUnexpected);

packages/cli/src/types.ts

@@ -1,3 +1,5 @@
+import type { Readable, Writable } from 'stream';
+
 export type ProjectSettings = import('@vercel/build-utils').ProjectSettings;
 
 export type Primitive =
@@ -442,3 +444,19 @@ export interface BuildOutput {
     layers?: string[];
   } | null;
 }
+
+export interface ReadableTTY extends Readable {
+  isTTY?: boolean;
+  isRaw?: boolean;
+  setRawMode?: (mode: boolean) => void;
+}
+
+export interface WritableTTY extends Writable {
+  isTTY?: boolean;
+}
+
+export interface Stdio {
+  stdin: ReadableTTY;
+  stdout: WritableTTY;
+  stderr: WritableTTY;
+}

packages/cli/src/util/bisect/normalize-url.ts

@@ -0,0 +1,7 @@
+function hasScheme(url: string): Boolean {
+  return url.startsWith('http://') || url.startsWith('https://');
+}
+
+export function normalizeURL(url: string): string {
+  return hasScheme(url) ? url : `https://${url}`;
+}

packages/cli/src/util/build/write-build-result.ts

@@ -385,8 +385,14 @@ export async function* findDirs(
   }
   for (const path of paths) {
     const abs = join(dir, path);
-    const s = await fs.stat(abs);
-    if (s.isDirectory()) {
+    let stat: fs.Stats;
+    try {
+      stat = await fs.lstat(abs);
+    } catch (err: any) {
+      if (err.code === 'ENOENT') continue;
+      throw err;
+    }
+    if (stat.isDirectory()) {
       if (path === name) {
         yield relative(root, abs);
       } else {

packages/cli/src/util/client.ts

@@ -1,3 +1,5 @@
+import { bold } from 'chalk';
+import inquirer from 'inquirer';
 import { EventEmitter } from 'events';
 import { URLSearchParams } from 'url';
 import { parse as parseUrl } from 'url';
@@ -11,10 +13,16 @@ import printIndications from './print-indications';
 import reauthenticate from './login/reauthenticate';
 import { SAMLError } from './login/types';
 import { writeToAuthConfigFile } from './config/files';
-import { AuthConfig, GlobalConfig, JSONObject } from '../types';
+import type {
+  AuthConfig,
+  GlobalConfig,
+  JSONObject,
+  Stdio,
+  ReadableTTY,
+  WritableTTY,
+} from '../types';
 import { sharedPromise } from './promise';
 import { APIError } from './errors-ts';
-import { bold } from 'chalk';
 
 const isSAMLError = (v: any): v is SAMLError => {
   return v && v.saml;
@@ -28,7 +36,7 @@ export interface FetchOptions extends Omit<RequestInit, 'body'> {
   accountId?: string;
 }
 
-export interface ClientOptions {
+export interface ClientOptions extends Stdio {
   argv: string[];
   apiUrl: string;
   authConfig: AuthConfig;
@@ -41,13 +49,17 @@ export const isJSONObject = (v: any): v is JSONObject => {
   return v && typeof v == 'object' && v.constructor === Object;
 };
 
-export default class Client extends EventEmitter {
+export default class Client extends EventEmitter implements Stdio {
   argv: string[];
   apiUrl: string;
   authConfig: AuthConfig;
+  stdin: ReadableTTY;
+  stdout: WritableTTY;
+  stderr: WritableTTY;
   output: Output;
   config: GlobalConfig;
   localConfig?: VercelConfig;
+  prompt!: inquirer.PromptModule;
   private requestIdCounter: number;
 
   constructor(opts: ClientOptions) {
@@ -55,10 +67,14 @@ export default class Client extends EventEmitter {
     this.argv = opts.argv;
     this.apiUrl = opts.apiUrl;
     this.authConfig = opts.authConfig;
+    this.stdin = opts.stdin;
+    this.stdout = opts.stdout;
+    this.stderr = opts.stderr;
     this.output = opts.output;
     this.config = opts.config;
     this.localConfig = opts.localConfig;
     this.requestIdCounter = 1;
+    this._createPromptModule();
   }
 
   retry<T>(fn: RetryFunction<T>, { retries = 3, maxTimeout = Infinity } = {}) {
@@ -124,7 +140,7 @@ export default class Client extends EventEmitter {
     return this.retry(async bail => {
       const res = await this._fetch(url, opts);
 
-      printIndications(res);
+      printIndications(this, res);
 
       if (!res.ok) {
         const error = await responseError(res);
@@ -180,4 +196,11 @@ export default class Client extends EventEmitter {
   _onRetry = (error: Error) => {
     this.output.debug(`Retrying: ${error}\n${error.stack}`);
   };
+
+  _createPromptModule() {
+    this.prompt = inquirer.createPromptModule({
+      input: this.stdin as NodeJS.ReadStream,
+      output: this.stderr as NodeJS.WriteStream,
+    });
+  }
 }

packages/cli/src/util/dev/builder.ts

@@ -13,8 +13,8 @@ import {
   Lambda,
   FileBlob,
   FileFsRef,
-  isOfficialRuntime,
 } from '@vercel/build-utils';
+import { isOfficialRuntime } from '@vercel/fs-detectors';
 import plural from 'pluralize';
 import minimatch from 'minimatch';
 
@@ -425,10 +425,6 @@ export async function getBuildMatches(
       src = extensionless;
     }
 
-    // We need to escape brackets since `glob` will
-    // try to find a group otherwise
-    src = src.replace(/(\[|\])/g, '[$1]');
-
     const files = fileList
       .filter(name => name === src || minimatch(name, src, { dot: true }))
       .map(name => join(cwd, name));

packages/cli/src/util/dev/headers.ts

@@ -0,0 +1,18 @@
+import { Headers } from 'node-fetch';
+import { IncomingHttpHeaders, OutgoingHttpHeaders } from 'http';
+
+export function nodeHeadersToFetchHeaders(
+  nodeHeaders: IncomingHttpHeaders | OutgoingHttpHeaders
+): Headers {
+  const headers = new Headers();
+  for (const [name, value] of Object.entries(nodeHeaders)) {
+    if (Array.isArray(value)) {
+      for (const val of value) {
+        headers.append(name, val);
+      }
+    } else if (typeof value !== 'undefined') {
+      headers.set(name, String(value));
+    }
+  }
+  return headers;
+}

packages/cli/src/util/dev/server.ts

@@ -1,12 +1,13 @@
+import ms from 'ms';
 import url, { URL } from 'url';
 import http from 'http';
 import fs from 'fs-extra';
 import chalk from 'chalk';
+import fetch from 'node-fetch';
 import plural from 'pluralize';
 import rawBody from 'raw-body';
 import listen from 'async-listen';
 import minimatch from 'minimatch';
-import ms from 'ms';
 import httpProxy from 'http-proxy';
 import { randomBytes } from 'crypto';
 import serveHandler from 'serve-handler';
@@ -16,11 +17,11 @@ import path, { isAbsolute, basename, dirname, extname, join } from 'path';
 import once from '@tootallnate/once';
 import directoryTemplate from 'serve-handler/src/directory';
 import getPort from 'get-port';
-import { ChildProcess } from 'child_process';
 import isPortReachable from 'is-port-reachable';
 import deepEqual from 'fast-deep-equal';
 import which from 'which';
 import npa from 'npm-package-arg';
+import type { ChildProcess } from 'child_process';
 
 import { getVercelIgnore, fileNameSymbol } from '@vercel/client';
 import {
@@ -35,12 +36,14 @@ import {
   StartDevServerResult,
   FileFsRef,
   PackageJson,
+  spawnCommand,
+} from '@vercel/build-utils';
+import {
   detectBuilders,
   detectApiDirectory,
   detectApiExtensions,
-  spawnCommand,
   isOfficialRuntime,
-} from '@vercel/build-utils';
+} from '@vercel/fs-detectors';
 import frameworkList from '@vercel/frameworks';
 
 import cmd from '../output/cmd';
@@ -90,6 +93,7 @@ import {
 import { ProjectEnvVariable, ProjectSettings } from '../../types';
 import exposeSystemEnvs from './expose-system-envs';
 import { treeKill } from '../tree-kill';
+import { nodeHeadersToFetchHeaders } from './headers';
 
 const frontendRuntimeSet = new Set(
   frameworkList.map(f => f.useRuntime?.use || '@vercel/static-build')
@@ -327,6 +331,8 @@ export default class DevServer {
   ): Promise<void> {
     const name = relative(this.cwd, fsPath);
     try {
+      await this.getVercelConfig();
+
       this.files[name] = await FileFsRef.fromFsPath({ fsPath });
       const extensionless = this.getExtensionlessFile(name);
       if (extensionless) {
@@ -593,7 +599,7 @@ export default class DevServer {
         await this.exit();
       }
 
-      if (warnings && warnings.length > 0) {
+      if (warnings?.length > 0) {
         warnings.forEach(warning =>
           this.output.warn(warning.message, null, warning.link, warning.action)
         );
@@ -1106,6 +1112,7 @@ export default class DevServer {
         view = errorTemplate({
           http_status_code: statusCode,
           http_status_description,
+          error_code,
           request_id: requestId,
         });
       }
@@ -1337,32 +1344,6 @@ export default class DevServer {
     return false;
   };
 
-  /*
-  runDevMiddleware = async (
-    req: http.IncomingMessage,
-    res: http.ServerResponse
-  ) => {
-    const { devMiddlewarePlugins } = await loadCliPlugins(
-      this.cwd,
-      this.output
-    );
-    try {
-      for (let plugin of devMiddlewarePlugins) {
-        const result = await plugin.plugin.runDevMiddleware(req, res, this.cwd);
-        if (result.finished) {
-          return result;
-        }
-      }
-      return { finished: false };
-    } catch (e) {
-      return {
-        finished: true,
-        error: e,
-      };
-    }
-  };
-  */
-
   /**
    * Serve project directory as a v2 deployment.
    */
@@ -1429,13 +1410,143 @@ export default class DevServer {
     let statusCode: number | undefined;
     let prevUrl = req.url;
     let prevHeaders: HttpHeadersConfig = {};
+    let middlewarePid: number | undefined;
 
-    /*
-    const middlewareResult = await this.runDevMiddleware(req, res);
+    // Run the middleware file, if present, and apply any
+    // mutations to the incoming request based on the
+    // result of the middleware invocation.
+    const middleware = [...this.buildMatches.values()].find(
+      m => m.config?.middleware === true
+    );
+    if (middleware) {
+      let startMiddlewareResult: StartDevServerResult | undefined;
+      // TODO: can we add some caching to prevent (re-)starting
+      // the middleware server for every HTTP request?
+      const { envConfigs, files, devCacheDir, cwd: workPath } = this;
+      try {
+        startMiddlewareResult =
+          await middleware.builderWithPkg.builder.startDevServer?.({
+            files,
+            entrypoint: middleware.entrypoint,
+            workPath,
+            repoRootPath: this.cwd,
+            config: middleware.config || {},
+            meta: {
+              isDev: true,
+              devCacheDir,
+              requestUrl: req.url,
+              env: { ...envConfigs.runEnv },
+              buildEnv: { ...envConfigs.buildEnv },
+            },
+          });
 
-    if (middlewareResult) {
-      if (middlewareResult.error) {
-        this.sendError(
+        if (startMiddlewareResult) {
+          const { port, pid } = startMiddlewareResult;
+          middlewarePid = pid;
+          this.devServerPids.add(pid);
+
+          const middlewareReqHeaders = nodeHeadersToFetchHeaders(req.headers);
+
+          // Add the Vercel platform proxy request headers
+          const proxyHeaders = this.getProxyHeaders(req, requestId, true);
+          for (const [name, value] of nodeHeadersToFetchHeaders(proxyHeaders)) {
+            middlewareReqHeaders.set(name, value);
+          }
+
+          const middlewareRes = await fetch(
+            `http://127.0.0.1:${port}${parsed.path}`,
+            {
+              headers: middlewareReqHeaders,
+              method: req.method,
+              redirect: 'manual',
+            }
+          );
+
+          if (middlewareRes.status === 500) {
+            await this.sendError(
+              req,
+              res,
+              requestId,
+              'EDGE_FUNCTION_INVOCATION_FAILED',
+              500
+            );
+            return;
+          }
+
+          // Apply status code from middleware invocation,
+          // for i.e. redirects or a custom 404 page
+          res.statusCode = middlewareRes.status;
+
+          let rewritePath = '';
+          let contentType = '';
+          let shouldContinue = false;
+          const skipMiddlewareHeaders = new Set([
+            'date',
+            'connection',
+            'content-length',
+            'transfer-encoding',
+          ]);
+          for (const [name, value] of middlewareRes.headers) {
+            if (name === 'x-middleware-next') {
+              shouldContinue = value === '1';
+            } else if (name === 'x-middleware-rewrite') {
+              rewritePath = value;
+              shouldContinue = true;
+            } else if (name === 'content-type') {
+              contentType = value;
+            } else if (!skipMiddlewareHeaders.has(name)) {
+              // Any other kind of response header should be included
+              // on both the incoming HTTP request (for when proxying
+              // to another function) and the outgoing HTTP response.
+              res.setHeader(name, value);
+              req.headers[name] = value;
+            }
+          }
+
+          if (!shouldContinue) {
+            const middlewareBody = await middlewareRes.buffer();
+            this.setResponseHeaders(res, requestId);
+            if (middlewareBody.length > 0) {
+              res.setHeader('content-length', middlewareBody.length);
+              if (contentType) {
+                res.setHeader('content-type', contentType);
+              }
+              res.end(middlewareBody);
+            } else {
+              res.end();
+            }
+            return;
+          }
+
+          if (rewritePath) {
+            // TODO: add validation?
+            debug(`Detected rewrite path from middleware: "${rewritePath}"`);
+            prevUrl = rewritePath;
+
+            // Retain orginal pathname, but override query parameters from the rewrite
+            const beforeRewriteUrl = req.url || '/';
+            const rewriteUrlParsed = url.parse(beforeRewriteUrl, true);
+            delete rewriteUrlParsed.search;
+            rewriteUrlParsed.query = url.parse(rewritePath, true).query;
+            req.url = url.format(rewriteUrlParsed);
+            debug(
+              `Rewrote incoming HTTP URL from "${beforeRewriteUrl}" to "${req.url}"`
+            );
+          }
+        }
+      } catch (err) {
+        // `startDevServer()` threw an error. Most likely this means the dev
+        // server process exited before sending the port information message
+        // (missing dependency at runtime, for example).
+        if (err.code === 'ENOENT') {
+          err.message = `Command not found: ${chalk.cyan(
+            err.path,
+            ...err.spawnargs
+          )}\nPlease ensure that ${cmd(err.path)} is properly installed`;
+          err.link = 'https://vercel.link/command-not-found';
+        }
+
+        await this.sendError(
           req,
           res,
           requestId,
@@ -1443,24 +1554,12 @@ export default class DevServer {
           500
         );
         return;
-      }
-      if (middlewareResult.finished) {
-        return;
-      }
-
-      if (middlewareResult.pathname) {
-        const origUrl = url.parse(req.url || '/', true);
-        origUrl.pathname = middlewareResult.pathname;
-        prevUrl = url.format(origUrl);
-      }
-      if (middlewareResult.query && prevUrl) {
-        const origUrl = url.parse(req.url || '/', true);
-        delete origUrl.search;
-        Object.assign(origUrl.query, middlewareResult.query);
-        prevUrl = url.format(origUrl);
+      } finally {
+        if (middlewarePid) {
+          this.killBuilderDevServer(middlewarePid);
+        }
       }
     }
-    */
 
     for (const phase of phases) {
       statusCode = undefined;
@@ -1740,7 +1839,10 @@ export default class DevServer {
             isDev: true,
             requestPath,
             devCacheDir,
-            env: { ...envConfigs.runEnv },
+            env: {
+              ...envConfigs.runEnv,
+              VERCEL_BUILDER_DEBUG: this.output.debugEnabled ? '1' : undefined,
+            },
             buildEnv: { ...envConfigs.buildEnv },
           },
         });
@@ -2185,13 +2287,7 @@ function proxyPass(
         `Failed to complete request to ${req.url}: ${error}`
       );
       if (!res.headersSent) {
-        devServer.sendError(
-          req,
-          res,
-          requestId,
-          'NO_RESPONSE_FROM_FUNCTION',
-          502
-        );
+        devServer.sendError(req, res, requestId, 'FUNCTION_INVOCATION_FAILED');
       }
     }
   );
@@ -2269,11 +2365,12 @@ async function findBuildMatch(
       if (!isIndex(match.src)) {
         return match;
       } else {
-        // if isIndex === true and ends in .html, we're done. Otherwise, keep searching
-        bestIndexMatch = match;
+        // If isIndex === true and ends in `.html`, we're done.
+        // Otherwise, keep searching.
         if (extname(match.src) === '.html') {
-          return bestIndexMatch;
+          return match;
         }
+        bestIndexMatch = match;
       }
     }
   }
@@ -2295,6 +2392,13 @@ async function shouldServe(
     config,
     builderWithPkg: { builder },
   } = match;
+
+  // "middleware" file is not served as a regular asset,
+  // instead it gets invoked as part of the routing logic.
+  if (config?.middleware === true) {
+    return false;
+  }
+
   const cleanSrc = src.endsWith('.html') ? src.slice(0, -5) : src;
   const trimmedPath = requestPath.endsWith('/')
     ? requestPath.slice(0, -1)

packages/cli/src/util/dns/get-dns-data.ts

@@ -2,26 +2,29 @@ import chalk from 'chalk';
 import { DNSRecordData } from '../../types';
 import textInput from '../input/text';
 import promptBool from '../input/prompt-bool';
-import { Output } from '../output';
+import Client from '../client';
 
 const RECORD_TYPES = ['A', 'AAAA', 'ALIAS', 'CAA', 'CNAME', 'MX', 'SRV', 'TXT'];
 
 export default async function getDNSData(
-  output: Output,
+  client: Client,
   data: null | DNSRecordData
 ): Promise<DNSRecordData | null> {
   if (data) {
     return data;
   }
+  const { output } = client;
 
   try {
     // first ask for type, branch from there
     const possibleTypes = new Set(RECORD_TYPES);
-    const type = (await textInput({
-      label: `- Record type (${RECORD_TYPES.join(', ')}): `,
-      validateValue: (v: string) =>
-        Boolean(v && possibleTypes.has(v.trim().toUpperCase()))
-    }))
+    const type = (
+      await textInput({
+        label: `- Record type (${RECORD_TYPES.join(', ')}): `,
+        validateValue: (v: string) =>
+          Boolean(v && possibleTypes.has(v.trim().toUpperCase())),
+      })
+    )
       .trim()
       .toUpperCase();
 
@@ -39,7 +42,7 @@ export default async function getDNSData(
           target
         )}.`
       );
-      return (await verifyData())
+      return (await verifyData(client))
         ? {
             name,
             type,
@@ -47,8 +50,8 @@ export default async function getDNSData(
               priority,
               weight,
               port,
-              target
-            }
+              target,
+            },
           }
         : null;
     }
@@ -61,23 +64,23 @@ export default async function getDNSData(
           `${mxPriority}`
         )} ${chalk.cyan(value)}`
       );
-      return (await verifyData())
+      return (await verifyData(client))
         ? {
             name,
             type,
             value,
-            mxPriority
+            mxPriority,
           }
         : null;
     }
 
     const value = await getTrimmedString(`- ${type} value: `);
     output.log(`${chalk.cyan(name)} ${chalk.bold(type)} ${chalk.cyan(value)}`);
-    return (await verifyData())
+    return (await verifyData(client))
       ? {
           name,
           type,
-          value
+          value,
         }
       : null;
   } catch (error) {
@@ -85,13 +88,13 @@ export default async function getDNSData(
   }
 }
 
-async function verifyData() {
-  return promptBool('Is this correct?');
+async function verifyData(client: Client) {
+  return promptBool('Is this correct?', client);
 }
 
 async function getRecordName(type: string) {
   const input = await textInput({
-    label: `- ${type} name: `
+    label: `- ${type} name: `,
   });
   return input === '@' ? '' : input;
 }
@@ -100,14 +103,14 @@ async function getNumber(label: string) {
   return Number(
     await textInput({
       label,
-      validateValue: v => Boolean(v && Number(v))
+      validateValue: v => Boolean(v && Number(v)),
     })
   );
 }
 async function getTrimmedString(label: string) {
   const res = await textInput({
     label,
-    validateValue: v => Boolean(v && v.trim().length > 0)
+    validateValue: v => Boolean(v && v.trim().length > 0),
   });
   return res.trim();
 }

packages/cli/src/util/domains/purchase-domain-if-available.ts

@@ -54,7 +54,8 @@ export default async function purchaseDomainIfAvailable(
       !(await promptBool(
         `Buy ${chalk.underline(domain)} for ${chalk.bold(
           `$${price}`
-        )} (${plural('yr', period, true)})?`
+        )} (${plural('yr', period, true)})?`,
+        client
       ))
     ) {
       output.print(eraseLines(1));

packages/cli/src/util/get-files.ts

@@ -1,5 +1,5 @@
-import { resolve } from 'path';
 import fs from 'fs-extra';
+import { resolve } from 'path';
 import { getVercelIgnore } from '@vercel/client';
 import uniqueStrings from './unique-strings';
 import { Output } from './output/create-output';

packages/cli/src/util/index.ts

@@ -530,7 +530,7 @@ export default class Now extends EventEmitter {
       `${opts.method || 'GET'} ${this._apiUrl}${_url} ${opts.body || ''}`,
       fetch(`${this._apiUrl}${_url}`, { ...opts, body })
     );
-    printIndications(res);
+    printIndications(this._client, res);
     return res;
   }
 

packages/cli/src/util/input/confirm.ts

@@ -1,12 +1,13 @@
-import inquirer from 'inquirer';
+import Client from '../client';
 
 export default async function confirm(
+  client: Client,
   message: string,
   preferred: boolean
 ): Promise<boolean> {
   require('./patch-inquirer');
 
-  const answers = await inquirer.prompt({
+  const answers = await client.prompt({
     type: 'confirm',
     name: 'value',
     message,

packages/cli/src/util/input/edit-project-settings.ts

@@ -1,8 +1,8 @@
 import inquirer from 'inquirer';
 import confirm from './confirm';
 import chalk from 'chalk';
-import { Output } from '../output';
 import frameworkList, { Framework } from '@vercel/frameworks';
+import Client from '../client';
 import { isSettingValue } from '../is-setting-value';
 import { ProjectSettings } from '../../types';
 
@@ -22,12 +22,14 @@ const settingKeys = Object.keys(settingMap).sort() as unknown as readonly [
 export type PartialProjectSettings = Pick<ProjectSettings, ConfigKeys>;
 
 export default async function editProjectSettings(
-  output: Output,
+  client: Client,
   projectSettings: PartialProjectSettings | null,
   framework: Framework | null,
   autoConfirm: boolean,
   localConfigurationOverrides: PartialProjectSettings | null
 ): Promise<ProjectSettings> {
+  const { output } = client;
+
   // Create initial settings object defaulting everything to `null` and assigning what may exist in `projectSettings`
   const settings: ProjectSettings = Object.assign(
     {
@@ -118,7 +120,7 @@ export default async function editProjectSettings(
   // Prompt the user if they want to modify any settings not defined by local configuration.
   if (
     autoConfirm ||
-    !(await confirm('Want to modify these settings?', false))
+    !(await confirm(client, 'Want to modify these settings?', false))
   ) {
     return settings;
   }

packages/cli/src/util/input/input-project.ts

@@ -1,5 +1,4 @@
 import Client from '../client';
-import inquirer from 'inquirer';
 import confirm from './confirm';
 import getProjectByIdOrName from '../projects/get-project-by-id-or-name';
 import chalk from 'chalk';
@@ -47,11 +46,16 @@ export default async function inputProject(
 
   if (!detectedProject) {
     // did not auto-detect a project to link
-    shouldLinkProject = await confirm(`Link to existing project?`, false);
+    shouldLinkProject = await confirm(
+      client,
+      `Link to existing project?`,
+      false
+    );
   } else {
     // auto-detected a project to link
     if (
       await confirm(
+        client,
         `Found project ${chalk.cyan(
           `“${org.slug}/${detectedProject.name}”`
         )}. Link to it?`,
@@ -63,6 +67,7 @@ export default async function inputProject(
 
     // user doesn't want to link the auto-detected project
     shouldLinkProject = await confirm(
+      client,
       `Link to different existing project?`,
       true
     );
@@ -73,7 +78,7 @@ export default async function inputProject(
     let project: Project | ProjectNotFound | null = null;
 
     while (!project || project instanceof ProjectNotFound) {
-      const answers = await inquirer.prompt({
+      const answers = await client.prompt({
         type: 'input',
         name: 'existingProjectName',
         message: `What’s the name of your existing project?`,
@@ -104,7 +109,7 @@ export default async function inputProject(
   let newProjectName: string | null = null;
 
   while (!newProjectName) {
-    const answers = await inquirer.prompt({
+    const answers = await client.prompt({
       type: 'input',
       name: 'newProjectName',
       message: `What’s your project’s name?`,

packages/cli/src/util/input/input-root-directory.ts

@@ -1,12 +1,11 @@
 import path from 'path';
 import chalk from 'chalk';
-import inquirer from 'inquirer';
-import { Output } from '../output';
 import { validateRootDirectory } from '../validate-paths';
+import Client from '../client';
 
 export async function inputRootDirectory(
+  client: Client,
   cwd: string,
-  output: Output,
   autoConfirm = false
 ) {
   if (autoConfirm) {
@@ -15,7 +14,7 @@ export async function inputRootDirectory(
 
   // eslint-disable-next-line no-constant-condition
   while (true) {
-    const { rootDirectory } = await inquirer.prompt({
+    const { rootDirectory } = await client.prompt({
       type: 'input',
       name: 'rootDirectory',
       message: `In which directory is your code located?`,
@@ -38,7 +37,7 @@ export async function inputRootDirectory(
 
     if (
       (await validateRootDirectory(
-        output,
+        client.output,
         cwd,
         fullPath,
         'Please choose a different one.'

packages/cli/src/util/input/list.ts

@@ -1,5 +1,6 @@
 import inquirer from 'inquirer';
 import stripAnsi from 'strip-ansi';
+import Client from '../client';
 import eraseLines from '../output/erase-lines';
 
 interface ListEntry {
@@ -35,21 +36,24 @@ function getLength(input: string): number {
   return biggestLength;
 }
 
-export default async function list({
-  message = 'the question',
-  // eslint-disable-line no-unused-vars
-  choices: _choices = [
-    {
-      name: 'something\ndescription\ndetails\netc',
-      value: 'something unique',
-      short: 'generally the first line of `name`',
-    },
-  ],
-  pageSize = 15, // Show 15 lines without scrolling (~4 credit cards)
-  separator = false, // Puts a blank separator between each choice
-  abort = 'end', // Whether the `abort` option will be at the `start` or the `end`,
-  eraseFinalAnswer = false, // If true, the line with the final answer that inquirer prints will be erased before returning
-}: ListOptions): Promise<string> {
+export default async function list(
+  client: Client,
+  {
+    message = 'the question',
+    // eslint-disable-line no-unused-vars
+    choices: _choices = [
+      {
+        name: 'something\ndescription\ndetails\netc',
+        value: 'something unique',
+        short: 'generally the first line of `name`',
+      },
+    ],
+    pageSize = 15, // Show 15 lines without scrolling (~4 credit cards)
+    separator = false, // Puts a blank separator between each choice
+    abort = 'end', // Whether the `abort` option will be at the `start` or the `end`,
+    eraseFinalAnswer = false, // If true, the line with the final answer that inquirer prints will be erased before returning
+  }: ListOptions
+): Promise<string> {
   require('./patch-inquirer-legacy');
 
   let biggestLength = 0;
@@ -106,7 +110,7 @@ export default async function list({
     choices.push(abortSeparator, _abort);
   }
 
-  const answer = await inquirer.prompt({
+  const answer = await client.prompt({
     name: 'value',
     type: 'list',
     default: selected,

packages/cli/src/util/input/prompt-bool.ts

@@ -1,25 +1,26 @@
 import chalk from 'chalk';
+import type { ReadableTTY, WritableTTY } from '../../types';
 
 type Options = {
   abortSequences?: Set<string>;
   defaultValue?: boolean;
   noChar?: string;
   resolveChars?: Set<string>;
-  stdin?: NodeJS.ReadStream;
-  stdout?: NodeJS.WriteStream;
+  stdin: ReadableTTY;
+  stdout: WritableTTY;
   trailing?: string;
   yesChar?: string;
 };
 
-export default async function promptBool(label: string, options: Options = {}) {
+export default async function promptBool(label: string, options: Options) {
   const {
+    stdin,
+    stdout,
     defaultValue = false,
     abortSequences = new Set(['\u0003']),
     resolveChars = new Set(['\r']),
     yesChar = 'y',
     noChar = 'n',
-    stdin = process.stdin,
-    stdout = process.stdout,
     trailing = '',
   } = options;
 

packages/cli/src/util/input/read-standard-input.ts

@@ -1,13 +1,17 @@
-export default async function readStandardInput(): Promise<string> {
+import type { ReadableTTY } from '../../types';
+
+export default async function readStandardInput(
+  stdin: ReadableTTY
+): Promise<string> {
   return new Promise<string>(resolve => {
     setTimeout(() => resolve(''), 500);
 
-    if (process.stdin.isTTY) {
+    if (stdin.isTTY) {
       // found tty so we know there is nothing piped to stdin
       resolve('');
     } else {
-      process.stdin.setEncoding('utf8');
-      process.stdin.once('data', resolve);
+      stdin.setEncoding('utf8');
+      stdin.once('data', resolve);
     }
   });
 }

packages/cli/src/util/link/setup-and-link.ts

@@ -56,7 +56,7 @@ export default async function setupAndLink(
     return { status: 'error', exitCode: 1, reason: 'PATH_IS_FILE' };
   }
   const link = await getLinkedProject(client, path);
-  const isTTY = process.stdout.isTTY;
+  const isTTY = client.stdin.isTTY;
   const quiet = !isTTY;
   let rootDirectory: string | null = null;
   let sourceFilesOutsideRootDirectory = true;
@@ -80,6 +80,7 @@ export default async function setupAndLink(
   const shouldStartSetup =
     autoConfirm ||
     (await confirm(
+      client,
       `${setupMsg} ${chalk.cyan(`“${toHumanPath(path)}”`)}?`,
       true
     ));
@@ -120,7 +121,7 @@ export default async function setupAndLink(
 
   if (typeof projectOrNewProjectName === 'string') {
     newProjectName = projectOrNewProjectName;
-    rootDirectory = await inputRootDirectory(path, output, autoConfirm);
+    rootDirectory = await inputRootDirectory(client, path, autoConfirm);
   } else {
     const project = projectOrNewProjectName;
 
@@ -224,7 +225,7 @@ export default async function setupAndLink(
       const { projectSettings, framework } = deployment;
 
       settings = await editProjectSettings(
-        output,
+        client,
         projectSettings,
         framework,
         autoConfirm,

packages/cli/src/util/login/oauth.ts

@@ -176,7 +176,7 @@ async function getVerificationTokenOutOfBand(client: Client, url: URL) {
   output.log(
     `After login is complete, enter the verification code printed in your browser.`
   );
-  const verificationToken = await readInput('Verification code:');
+  const verificationToken = await readInput(client, 'Verification code:');
   output.print(eraseLines(6));
 
   // If the pasted token begins with "saml_", then the `ssoUserId` was returned.

packages/cli/src/util/login/prompt.ts

@@ -1,4 +1,3 @@
-import inquirer from 'inquirer';
 import Client from '../client';
 import error from '../output/error';
 import listInput from '../input/list';
@@ -32,7 +31,7 @@ export default async function prompt(
     choices.pop();
   }
 
-  const choice = await listInput({
+  const choice = await listInput(client, {
     message: 'Log in to Vercel',
     choices,
   });
@@ -44,22 +43,26 @@ export default async function prompt(
   } else if (choice === 'bitbucket') {
     result = await doBitbucketLogin(client, outOfBand, ssoUserId);
   } else if (choice === 'email') {
-    const email = await readInput('Enter your email address:');
+    const email = await readInput(client, 'Enter your email address:');
     result = await doEmailLogin(client, email, ssoUserId);
   } else if (choice === 'saml') {
-    const slug = error?.teamId || (await readInput('Enter your Team slug:'));
+    const slug =
+      error?.teamId || (await readInput(client, 'Enter your Team slug:'));
     result = await doSamlLogin(client, slug, outOfBand, ssoUserId);
   }
 
   return result;
 }
 
-export async function readInput(message: string): Promise<string> {
+export async function readInput(
+  client: Client,
+  message: string
+): Promise<string> {
   let input;
 
   while (!input) {
     try {
-      const { val } = await inquirer.prompt({
+      const { val } = await client.prompt({
         type: 'input',
         name: 'val',
         message,

packages/cli/src/util/login/reauthenticate.ts

@@ -14,7 +14,7 @@ export default async function reauthenticate(
     client.output.log(
       `You must re-authenticate with SAML to use ${bold(error.scope)} scope.`
     );
-    if (await confirm(`Log in with SAML?`, true)) {
+    if (await confirm(client, `Log in with SAML?`, true)) {
       return doSamlLogin(client, error.teamId);
     }
   } else {

packages/cli/src/util/output/create-output.ts

@@ -1,41 +1,39 @@
 import chalk from 'chalk';
 import renderLink from './link';
 import wait, { StopSpinner } from './wait';
-import { Writable } from 'stream';
+import type { WritableTTY } from '../../types';
 
 export interface OutputOptions {
   debug?: boolean;
 }
 
-export interface PrintOptions {
-  w?: Writable;
-}
-
-export interface LogOptions extends PrintOptions {
+export interface LogOptions {
   color?: typeof chalk;
 }
 
 export class Output {
+  stream: WritableTTY;
   debugEnabled: boolean;
   private spinnerMessage: string;
   private _spinner: StopSpinner | null;
-  isTTY: boolean;
 
-  constructor({ debug: debugEnabled = false }: OutputOptions = {}) {
+  constructor(
+    stream: WritableTTY,
+    { debug: debugEnabled = false }: OutputOptions = {}
+  ) {
+    this.stream = stream;
     this.debugEnabled = debugEnabled;
     this.spinnerMessage = '';
     this._spinner = null;
-    this.isTTY = process.stdout.isTTY || false;
   }
 
   isDebugEnabled = () => {
     return this.debugEnabled;
   };
 
-  print = (str: string, { w }: PrintOptions = { w: process.stderr }) => {
+  print = (str: string) => {
     this.stopSpinner();
-    const stream: Writable = w || process.stderr;
-    stream.write(str);
+    this.stream.write(str);
   };
 
   log = (str: string, color = chalk.grey) => {
@@ -111,11 +109,17 @@ export class Output {
       this.debug(`Spinner invoked (${message}) with a ${delay}ms delay`);
       return;
     }
-    if (this.isTTY) {
+    if (this.stream.isTTY) {
       if (this._spinner) {
         this._spinner.text = message;
       } else {
-        this._spinner = wait(message, delay);
+        this._spinner = wait(
+          {
+            text: message,
+            stream: this.stream,
+          },
+          delay
+        );
       }
     } else {
       this.print(`${message}\n`);
@@ -157,7 +161,3 @@ export class Output {
     return promise;
   };
 }
-
-export default function createOutput(opts?: OutputOptions) {
-  return new Output(opts);
-}

packages/cli/src/util/output/index.ts

@@ -1,2 +1,2 @@
-export { default, Output } from './create-output';
+export { Output } from './create-output';
 export { StopSpinner } from './wait';

packages/cli/src/util/output/wait.ts

@@ -8,14 +8,19 @@ export interface StopSpinner {
 }
 
 export default function wait(
-  msg: string,
-  delay: number = 300,
-  _ora = ora
+  opts: ora.Options,
+  delay: number = 300
 ): StopSpinner {
-  let spinner: ReturnType<typeof _ora> | null = null;
+  let text = opts.text;
+  let spinner: ora.Ora | null = null;
+
+  if (typeof text !== 'string') {
+    throw new Error(`"text" is required for Ora spinner`);
+  }
 
   const timeout = setTimeout(() => {
-    spinner = _ora(chalk.gray(msg));
+    spinner = ora(opts);
+    spinner.text = chalk.gray(text);
     spinner.color = 'gray';
     spinner.start();
   }, delay);
@@ -29,23 +34,21 @@ export default function wait(
     }
   };
 
-  stop.text = msg;
+  stop.text = text;
 
   // Allow `text` property to update the text while the spinner is in action
   Object.defineProperty(stop, 'text', {
     get() {
-      return msg;
+      return text;
     },
 
     set(v: string) {
-      msg = v;
+      text = v;
       if (spinner) {
         spinner.text = chalk.gray(v);
       }
     },
   });
 
-  // @ts-ignore
-  process.once('nowExit', stop);
   return stop;
 }

packages/cli/src/util/print-indications.ts

@@ -1,11 +1,10 @@
 import chalk from 'chalk';
 import { Response } from 'node-fetch';
-import { emoji, EmojiLabel, prependEmoji } from './emoji';
-import createOutput from './output';
+import Client from './client';
 import linkStyle from './output/link';
+import { emoji, EmojiLabel, prependEmoji } from './emoji';
 
-export default function printIndications(res: Response) {
-  const _output = createOutput();
+export default function printIndications(client: Client, res: Response) {
   const indications = new Set(['warning', 'notice', 'tip']);
   const regex = /^x-(?:vercel|now)-(warning|notice|tip)-(.*)$/;
 
@@ -25,7 +24,7 @@ export default function printIndications(res: Response) {
             chalk.dim(`${action || 'Learn More'}: ${linkStyle(link)}`) +
             newline;
         }
-        _output.print(message + finalLink);
+        client.output.print(message + finalLink);
       }
     }
   }

packages/cli/src/util/validate-paths.ts

@@ -5,6 +5,7 @@ import chalk from 'chalk';
 import { homedir } from 'os';
 import confirm from './input/confirm';
 import toHumanPath from './humanize-path';
+import Client from './client';
 
 const stat = promisify(lstatRaw);
 
@@ -51,9 +52,11 @@ export async function validateRootDirectory(
 }
 
 export default async function validatePaths(
-  output: Output,
+  client: Client,
   paths: string[]
 ): Promise<{ valid: true; path: string } | { valid: false; exitCode: number }> {
+  const { output } = client;
+
   // can't deploy more than 1 path
   if (paths.length > 1) {
     output.print(`${chalk.red('Error!')} Can't deploy more than one path.\n`);
@@ -85,6 +88,7 @@ export default async function validatePaths(
   // ask confirmation if the directory is home
   if (path === homedir()) {
     const shouldDeployHomeDirectory = await confirm(
+      client,
       `You are deploying your home directory. Do you want to continue?`,
       false
     );

packages/cli/test/dev/fixtures/edge-function-error/api/edge-error-config.js

@@ -0,0 +1,7 @@
+export const config = {
+  runtime: 'invalid-runtime-value',
+};
+
+export default async function edge(request, event) {
+  throw new Error('intentional runtime error');
+}

packages/cli/test/dev/fixtures/edge-function-error/api/edge-error-no-handler.js

@@ -0,0 +1,8 @@
+export const config = {
+  runtime: 'experimental-edge',
+};
+
+export async function notTheDefaultExport(request, event) {
+  // this will never be run
+  return new Response('some response body');
+}

packages/cli/test/dev/fixtures/edge-function-error/api/edge-error-runtime.js

@@ -0,0 +1,7 @@
+export const config = {
+  runtime: 'experimental-edge',
+};
+
+export default async function edge(request, event) {
+  throw new Error('intentional runtime error');
+}

packages/cli/test/dev/fixtures/edge-function-error/api/edge-error-startup.js

@@ -0,0 +1,10 @@
+export const config = {
+  runtime: 'experimental-edge',
+};
+
+export default async function edge(request, event) {
+  // this should never be executed
+  return new Response('some response body');
+}
+
+throw new Error('intentional startup error');

packages/cli/test/dev/fixtures/edge-function-error/api/edge-error-syntax.js

@@ -0,0 +1,9 @@
+export const config = {
+  runtime: 'experimental-edge'
+}
+
+export default async function edge(request, event) {
+  return new Response('some response body');
+
+// intentional missing closing bracket to produce syntax error
+// }

packages/cli/test/dev/fixtures/edge-function-error/api/edge-error-unknown-import.js

@@ -0,0 +1,9 @@
+import unknownModule from 'unknown-module-893427589372458934795843';
+
+export const config = {
+  runtime: 'experimental-edge',
+};
+
+export default async function edge(request, event) {
+  return new Response(unknownModule('some response body'));
+}

packages/cli/test/dev/fixtures/edge-function/api/edge-500-response.js

@@ -0,0 +1,9 @@
+export const config = {
+  runtime: 'experimental-edge',
+};
+
+export default async function edge(request, event) {
+  return new Response('responding with intentional 500 from user code', {
+    status: 500,
+  });
+}

packages/cli/test/dev/fixtures/edge-function/yarn.lock

@@ -0,0 +1,8 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+decamelize@6.0.0:
+  version "6.0.0"
+  resolved "https://registry.yarnpkg.com/decamelize/-/decamelize-6.0.0.tgz#8cad4d916fde5c41a264a43d0ecc56fe3d31749e"
+  integrity sha512-Fv96DCsdOgB6mdGl67MT5JaTNKRzrzill5OH5s8bjYJXVlcXyPYGyPsUkWyGV5p1TXI5esYIYMMeDJL0hEIwaA==

packages/cli/test/dev/fixtures/middleware-500-response/middleware.js

@@ -0,0 +1 @@
+export default () => new Response(null, { status: 500 });

packages/cli/test/dev/fixtures/middleware-error-at-init/middleware.js

@@ -0,0 +1 @@
+throw new Error('Middleware init error');

packages/cli/test/dev/fixtures/middleware-error-in-handler/middleware.js

@@ -0,0 +1,3 @@
+export default () => {
+  throw new Error('Middleware handler error');
+};

packages/cli/test/dev/fixtures/middleware-matchers/middleware.js

@@ -0,0 +1,21 @@
+// Supports both a single string value or an array of matchers
+export const config = {
+  matcher: ['/about/:path*', '/dashboard/:path*'],
+};
+
+export default function middleware(request, _event) {
+  const url = new URL(request.url);
+
+  const response = new Response(
+    JSON.stringify({
+      pathname: url.pathname,
+      search: url.search,
+      fromMiddleware: true,
+    })
+  );
+
+  // Set custom header
+  response.headers.set('x-modified-edge', 'true');
+
+  return response;
+}

packages/cli/test/dev/fixtures/middleware-redirect/middleware.js

@@ -0,0 +1,9 @@
+export default req => {
+  const url = new URL(req.url);
+  return new Response(null, {
+    status: 302,
+    headers: {
+      location: `https://vercel.com${url.pathname}${url.search}`,
+    },
+  });
+};

packages/cli/test/dev/fixtures/middleware-response/middleware.js

@@ -0,0 +1 @@
+export default () => new Response('hi from middleware');

packages/cli/test/dev/fixtures/middleware-rewrite-query/api/fn.js

@@ -0,0 +1,5 @@
+export default (req, res) => {
+  res.json({
+    url: req.url,
+  });
+};

packages/cli/test/dev/fixtures/middleware-rewrite-query/middleware.js

@@ -0,0 +1,6 @@
+export default () =>
+  new Response(null, {
+    headers: {
+      'x-middleware-rewrite': '/api/fn?from-middleware=true',
+    },
+  });

packages/cli/test/dev/fixtures/middleware-rewrite/another.html

@@ -0,0 +1 @@
+<h1>Another</h1>

packages/cli/test/dev/fixtures/middleware-rewrite/index.html

@@ -0,0 +1 @@
+<h1>Index</h1>

packages/cli/test/dev/fixtures/middleware-rewrite/middleware.js

@@ -0,0 +1,19 @@
+export default req => {
+  const url = new URL(req.url);
+
+  if (url.pathname === '/') {
+    // Pass-through "index.html" page
+    return new Response(null, {
+      headers: {
+        'x-middleware-next': '1',
+      },
+    });
+  }
+
+  // Everything else goes to "another.html"
+  return new Response(null, {
+    headers: {
+      'x-middleware-rewrite': '/another.html',
+    },
+  });
+};

packages/cli/test/dev/fixtures/no-api/vercel.json

@@ -0,0 +1,3 @@
+{
+  "version": 2
+}

packages/cli/test/dev/integration-1.test.ts

@@ -23,7 +23,7 @@ test('[vercel dev] should support edge functions', async () => {
 
     const body = { hello: 'world' };
 
-    let res = await fetch(`http://localhost:${port}/api/edge-function`, {
+    let res = await fetch(`http://localhost:${port}/api/edge-success`, {
       method: 'POST',
       headers: {
         'content-type': 'application/json',
@@ -36,7 +36,7 @@ test('[vercel dev] should support edge functions', async () => {
     // are set up; so, we test that they are all passed through properly
     expect(await res.json()).toMatchObject({
       headerContentType: 'application/json',
-      url: `http://localhost:${port}/api/edge-function`,
+      url: `http://localhost:${port}/api/edge-success`,
       method: 'POST',
       body: '{"hello":"world"}',
       decamelized: 'some_camel_case_thing',
@@ -48,6 +48,235 @@ test('[vercel dev] should support edge functions', async () => {
   }
 });
 
+test(
+  '[vercel dev] edge functions respond properly the same as production',
+  testFixtureStdio('edge-function', async (testPath: any) => {
+    await testPath(500, '/api/edge-500-response');
+    await testPath(200, '/api/edge-success');
+  })
+);
+
+test('[vercel dev] should support edge functions returning intentional 500 responses', async () => {
+  const dir = fixture('edge-function');
+  const { dev, port, readyResolver } = await testFixture(dir);
+
+  try {
+    await readyResolver;
+
+    const body = { hello: 'world' };
+
+    let res = await fetch(`http://localhost:${port}/api/edge-500-response`, {
+      method: 'POST',
+      headers: {
+        'content-type': 'application/json',
+      },
+      body: JSON.stringify(body),
+    });
+    validateResponseHeaders(res);
+
+    expect(await res.status).toBe(500);
+    expect(await res.text()).toBe(
+      'responding with intentional 500 from user code'
+    );
+  } finally {
+    await dev.kill('SIGTERM');
+  }
+});
+
+test('[vercel dev] should handle runtime errors thrown in edge functions', async () => {
+  const dir = fixture('edge-function-error');
+  const { dev, port, readyResolver } = await testFixture(dir);
+
+  try {
+    await readyResolver;
+
+    let res = await fetch(`http://localhost:${port}/api/edge-error-runtime`, {
+      method: 'GET',
+      headers: {
+        Accept:
+          'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
+      },
+    });
+    validateResponseHeaders(res);
+
+    const { stdout, stderr } = await dev.kill('SIGTERM');
+
+    expect(await res.text()).toMatch(
+      /<strong>500<\/strong>: INTERNAL_SERVER_ERROR/g
+    );
+    expect(stdout).toMatch(/Unhandled rejection: intentional runtime error/g);
+    expect(stderr).toMatch(
+      /Failed to complete request to \/api\/edge-error-runtime: Error: socket hang up/g
+    );
+  } finally {
+    await dev.kill('SIGTERM');
+  }
+});
+
+test('[vercel dev] should handle config errors thrown in edge functions', async () => {
+  const dir = fixture('edge-function-error');
+  const { dev, port, readyResolver } = await testFixture(dir);
+
+  try {
+    await readyResolver;
+
+    let res = await fetch(`http://localhost:${port}/api/edge-error-config`, {
+      method: 'GET',
+      headers: {
+        Accept:
+          'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
+      },
+    });
+    validateResponseHeaders(res);
+
+    const { stderr } = await dev.kill('SIGTERM');
+
+    expect(await res.text()).toMatch(
+      /<strong>500<\/strong>: INTERNAL_SERVER_ERROR/g
+    );
+    expect(stderr).toMatch(
+      /Invalid function runtime "invalid-runtime-value" for "api\/edge-error-config.js". Valid runtimes are: \["experimental-edge"\]/g
+    );
+    expect(stderr).toMatch(
+      /Failed to complete request to \/api\/edge-error-config: Error: socket hang up/g
+    );
+  } finally {
+    await dev.kill('SIGTERM');
+  }
+});
+
+test('[vercel dev] should handle startup errors thrown in edge functions', async () => {
+  const dir = fixture('edge-function-error');
+  const { dev, port, readyResolver } = await testFixture(dir);
+
+  try {
+    await readyResolver;
+
+    let res = await fetch(`http://localhost:${port}/api/edge-error-startup`, {
+      method: 'GET',
+      headers: {
+        Accept:
+          'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
+      },
+    });
+    validateResponseHeaders(res);
+
+    const { stderr } = await dev.kill('SIGTERM');
+
+    expect(await res.text()).toMatch(
+      /<strong>500<\/strong>: INTERNAL_SERVER_ERROR/g
+    );
+    expect(stderr).toMatch(/Failed to instantiate edge runtime./g);
+    expect(stderr).toMatch(/intentional startup error/g);
+    expect(stderr).toMatch(
+      /Failed to complete request to \/api\/edge-error-startup: Error: socket hang up/g
+    );
+  } finally {
+    await dev.kill('SIGTERM');
+  }
+});
+
+test('[vercel dev] should handle syntax errors thrown in edge functions', async () => {
+  const dir = fixture('edge-function-error');
+  const { dev, port, readyResolver } = await testFixture(dir);
+
+  try {
+    await readyResolver;
+
+    let res = await fetch(`http://localhost:${port}/api/edge-error-syntax`, {
+      method: 'GET',
+      headers: {
+        Accept:
+          'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
+      },
+    });
+    validateResponseHeaders(res);
+
+    const { stderr } = await dev.kill('SIGTERM');
+
+    expect(await res.text()).toMatch(
+      /<strong>500<\/strong>: INTERNAL_SERVER_ERROR/g
+    );
+    expect(stderr).toMatch(/Failed to instantiate edge runtime./g);
+    expect(stderr).toMatch(/Unexpected end of file/g);
+    expect(stderr).toMatch(
+      /Failed to complete request to \/api\/edge-error-syntax: Error: socket hang up/g
+    );
+  } finally {
+    await dev.kill('SIGTERM');
+  }
+});
+
+test('[vercel dev] should handle import errors thrown in edge functions', async () => {
+  const dir = fixture('edge-function-error');
+  const { dev, port, readyResolver } = await testFixture(dir);
+
+  try {
+    await readyResolver;
+
+    let res = await fetch(
+      `http://localhost:${port}/api/edge-error-unknown-import`,
+      {
+        method: 'GET',
+        headers: {
+          Accept:
+            'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
+        },
+      }
+    );
+    validateResponseHeaders(res);
+
+    const { stderr } = await dev.kill('SIGTERM');
+
+    expect(await res.text()).toMatch(
+      /<strong>500<\/strong>: INTERNAL_SERVER_ERROR/g
+    );
+    expect(stderr).toMatch(
+      /Could not resolve "unknown-module-893427589372458934795843"/g
+    );
+    expect(stderr).toMatch(
+      /Failed to complete request to \/api\/edge-error-unknown-import: Error: socket hang up/g
+    );
+  } finally {
+    await dev.kill('SIGTERM');
+  }
+});
+
+test('[vercel dev] should handle missing handler errors thrown in edge functions', async () => {
+  const dir = fixture('edge-function-error');
+  const { dev, port, readyResolver } = await testFixture(dir);
+
+  try {
+    await readyResolver;
+
+    let res = await fetch(
+      `http://localhost:${port}/api/edge-error-no-handler`,
+      {
+        method: 'GET',
+        headers: {
+          Accept:
+            'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
+        },
+      }
+    );
+    validateResponseHeaders(res);
+
+    const { stdout, stderr } = await dev.kill('SIGTERM');
+
+    expect(await res.text()).toMatch(
+      /<strong>500<\/strong>: INTERNAL_SERVER_ERROR/g
+    );
+    expect(stdout).toMatch(
+      /No default export was found. Add a default export to handle requests./g
+    );
+    expect(stderr).toMatch(
+      /Failed to complete request to \/api\/edge-error-no-handler: Error: socket hang up/g
+    );
+  } finally {
+    await dev.kill('SIGTERM');
+  }
+});
+
 test('[vercel dev] should support request body', async () => {
   const dir = fixture('node-request-body');
   const { dev, port, readyResolver } = await testFixture(dir);

packages/cli/test/dev/integration-2.test.ts

@@ -1,7 +1,17 @@
 // eslint-disable-next-line
-import path from 'path';
+import { join } from 'path';
+import ms from 'ms';
+import fs, { mkdirp } from 'fs-extra';
 
-const { exec, fixture, testFixture, testFixtureStdio } = require('./utils.js');
+const {
+  exec,
+  fetch,
+  fixture,
+  sleep,
+  testFixture,
+  testFixtureStdio,
+  validateResponseHeaders,
+} = require('./utils.js');
 
 test('[vercel dev] validate redirects', async () => {
   const directory = fixture('invalid-redirects');
@@ -334,3 +344,44 @@ test(
     await testPath(200, '/', /A simple deployment with the Vercel API!/m);
   })
 );
+
+test(
+  '[vercel dev] add a `api/fn.ts` when `api` does not exist at startup`',
+  testFixtureStdio('no-api', async (_testPath: any, port: any) => {
+    const directory = fixture('no-api');
+    const apiDir = join(directory, 'api');
+
+    try {
+      {
+        const response = await fetch(`http://localhost:${port}/api/new-file`);
+        validateResponseHeaders(response);
+        expect(response.status).toBe(404);
+      }
+
+      const fileContents = `
+          export const config = {
+            runtime: 'experimental-edge'
+          }
+
+          export default async function edge(request, event) {
+            return new Response('from new file');
+          }
+        `;
+
+      await mkdirp(apiDir);
+      await fs.writeFile(join(apiDir, 'new-file.js'), fileContents);
+
+      // Wait until file events have been processed
+      await sleep(ms('1s'));
+
+      {
+        const response = await fetch(`http://localhost:${port}/api/new-file`);
+        validateResponseHeaders(response);
+        const body = await response.text();
+        expect(body.trim()).toBe('from new file');
+      }
+    } finally {
+      await fs.remove(apiDir);
+    }
+  })
+);

packages/cli/test/dev/integration-4.test.ts

@@ -433,3 +433,98 @@ test(
     await testPath(404, '/i-do-not-exist');
   })
 );
+
+test(
+  '[vercel dev] Middleware that returns a 200 response',
+  testFixtureStdio('middleware-response', async (testPath: any) => {
+    await testPath(200, '/', 'hi from middleware');
+    await testPath(200, '/another', 'hi from middleware');
+  })
+);
+
+test(
+  '[vercel dev] Middleware that does basic rewrite',
+  testFixtureStdio('middleware-rewrite', async (testPath: any) => {
+    await testPath(200, '/', '<h1>Index</h1>');
+    await testPath(200, '/index', '<h1>Another</h1>');
+    await testPath(200, '/another', '<h1>Another</h1>');
+    await testPath(200, '/another.html', '<h1>Another</h1>');
+    await testPath(200, '/foo', '<h1>Another</h1>');
+  })
+);
+
+test(
+  '[vercel dev] Middleware that rewrites with custom query params',
+  testFixtureStdio('middleware-rewrite-query', async (testPath: any) => {
+    await testPath(200, '/?foo=bar', '{"url":"/?from-middleware=true"}');
+    await testPath(
+      200,
+      '/another?foo=bar',
+      '{"url":"/another?from-middleware=true"}'
+    );
+    await testPath(
+      200,
+      '/api/fn?foo=bar',
+      '{"url":"/api/fn?from-middleware=true"}'
+    );
+  })
+);
+
+test(
+  '[vercel dev] Middleware that redirects',
+  testFixtureStdio('middleware-redirect', async (testPath: any) => {
+    await testPath(302, '/', null, {
+      location: 'https://vercel.com/',
+    });
+    await testPath(302, '/home', null, {
+      location: 'https://vercel.com/home',
+    });
+    await testPath(302, '/?foo=bar', null, {
+      location: 'https://vercel.com/?foo=bar',
+    });
+  })
+);
+
+test(
+  '[vercel dev] Middleware with error in function handler',
+  testFixtureStdio('middleware-error-in-handler', async (testPath: any) => {
+    await testPath(500, '/', /EDGE_FUNCTION_INVOCATION_FAILED/);
+  })
+);
+
+test(
+  '[vercel dev] Middleware with error at init',
+  testFixtureStdio('middleware-error-at-init', async (testPath: any) => {
+    await testPath(500, '/', /EDGE_FUNCTION_INVOCATION_FAILED/);
+  })
+);
+
+test(
+  '[vercel dev] Middleware with an explicit 500 response',
+  testFixtureStdio('middleware-500-response', async (testPath: any) => {
+    await testPath(500, '/', /EDGE_FUNCTION_INVOCATION_FAILED/);
+  })
+);
+
+test(
+  '[vercel dev] Middleware with `matchers` config',
+  testFixtureStdio('middleware-matchers', async (testPath: any) => {
+    await testPath(404, '/');
+    await testPath(404, '/another');
+    await testPath(
+      200,
+      '/about/page',
+      '{"pathname":"/about/page","search":"","fromMiddleware":true}'
+    );
+    await testPath(
+      200,
+      '/dashboard/home',
+      '{"pathname":"/dashboard/home","search":"","fromMiddleware":true}'
+    );
+    await testPath(
+      200,
+      '/dashboard/home?a=b',
+      '{"pathname":"/dashboard/home","search":"?a=b","fromMiddleware":true}'
+    );
+  })
+);

packages/cli/test/dev/utils.js

@@ -257,6 +257,10 @@ async function testFixture(directory, opts = {}, args = []) {
   dev.kill = async (...args) => {
     dev._kill(...args);
     await exitResolver;
+    return {
+      stdout,
+      stderr,
+    };
   };
 
   return {

packages/cli/test/integration.js

@@ -1958,7 +1958,7 @@ test('ensure we render a prompt when deploying home directory', async t => {
   t.is(exitCode, 0);
 
   t.true(
-    stdout.includes(
+    stderr.includes(
       'You are deploying your home directory. Do you want to continue? [y/N]'
     )
   );

packages/cli/test/mocks/client.ts

@@ -1,4 +1,8 @@
+// Register Jest matcher extensions for CLI unit tests
+import './matchers';
+
 import chalk from 'chalk';
+import { PassThrough } from 'stream';
 import { createServer, Server } from 'http';
 import express, { Express, Router } from 'express';
 import listen from 'async-listen';
@@ -11,23 +15,42 @@ chalk.level = 0;
 
 export type Scenario = Router;
 
+class MockStream extends PassThrough {
+  isTTY: boolean;
+
+  constructor() {
+    super();
+    this.isTTY = true;
+  }
+
+  // These is for the `ora` module
+  clearLine() {}
+  cursorTo() {}
+}
+
 export class MockClient extends Client {
-  mockServer?: Server;
-  mockOutput: jest.Mock<void, Parameters<Output['print']>>;
-  private app: Express;
+  stdin!: MockStream;
+  stdout!: MockStream;
+  stderr!: MockStream;
   scenario: Scenario;
+  mockServer?: Server;
+  private app: Express;
 
   constructor() {
     super({
-      argv: [],
       // Gets populated in `startMockServer()`
       apiUrl: '',
+
+      // Gets re-initialized for every test in `reset()`
+      argv: [],
       authConfig: {},
-      output: new Output(),
       config: {},
       localConfig: {},
+      stdin: new PassThrough(),
+      stdout: new PassThrough(),
+      stderr: new PassThrough(),
+      output: new Output(new PassThrough()),
     });
-    this.mockOutput = jest.fn();
 
     this.app = express();
     this.app.use(express.json());
@@ -53,27 +76,29 @@ export class MockClient extends Client {
   }
 
   reset() {
-    this.output = new Output();
-    this.mockOutput = jest.fn();
-    this.output.print = s => {
-      return this.mockOutput(s);
-    };
+    this.stdin = new MockStream();
+
+    this.stdout = new MockStream();
+    this.stdout.setEncoding('utf8');
+    this.stdout.end = () => {};
+    this.stdout.pause();
+
+    this.stderr = new MockStream();
+    this.stderr.setEncoding('utf8');
+    this.stderr.end = () => {};
+    this.stderr.pause();
+    this.stderr.isTTY = true;
+
+    this._createPromptModule();
+
+    this.output = new Output(this.stderr);
 
     this.argv = [];
     this.authConfig = {};
     this.config = {};
     this.localConfig = {};
 
-    // Just make this one silent
-    this.output.spinner = () => {};
-
     this.scenario = Router();
-
-    this.output.isTTY = true;
-  }
-
-  get outputBuffer() {
-    return this.mockOutput.mock.calls.map(c => c[0]).join('');
   }
 
   async startMockServer() {

packages/cli/test/mocks/matchers/index.ts

@@ -0,0 +1,65 @@
+/**
+ * This file registers the custom Jest "matchers" that are useful for
+ * writing CLI unit tests, and sets them up to be recognized by TypeScript.
+ *
+ * References:
+ *  - https://haspar.us/notes/adding-jest-custom-matchers-in-typescript
+ *  - https://gist.github.com/hasparus/4ebaa17ec5d3d44607f522bcb1cda9fb
+ */
+
+/// <reference types="@types/jest" />
+
+import * as matchers from './matchers';
+
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
+type Tail<T extends unknown[]> = T extends [infer _Head, ...infer Tail]
+  ? Tail
+  : never;
+
+type AnyFunction = (...args: any[]) => any;
+type PromiseFunction = (...args: any[]) => Promise<any>;
+
+type GetMatcherType<TP, TResult> = TP extends PromiseFunction
+  ? (...args: Tail<Parameters<TP>>) => Promise<TResult>
+  : TP extends AnyFunction
+  ? (...args: Tail<Parameters<TP>>) => TResult
+  : TP;
+
+//type T = GetMatcherType<typeof matchers['toOutput'], void>;
+
+type GetMatchersType<TMatchers, TResult> = {
+  [P in keyof TMatchers]: GetMatcherType<TMatchers[P], TResult>;
+};
+
+type FirstParam<T extends AnyFunction> = Parameters<T>[0];
+
+type OnlyMethodsWhereFirstArgIsOfType<TObject, TWantedFirstArg> = {
+  [P in keyof TObject]: TObject[P] extends AnyFunction
+    ? TWantedFirstArg extends FirstParam<TObject[P]>
+      ? TObject[P]
+      : [
+          `Error: this function is present only when received is:`,
+          FirstParam<TObject[P]>
+        ]
+    : TObject[P];
+};
+
+declare global {
+  // eslint-disable-next-line @typescript-eslint/no-namespace
+  namespace jest {
+    // eslint-disable-next-line @typescript-eslint/no-empty-interface
+    interface Matchers<R, T = {}>
+      extends GetMatchersType<
+        OnlyMethodsWhereFirstArgIsOfType<typeof matchers, T>,
+        R
+      > {}
+  }
+}
+
+const jestExpect = (global as any).expect;
+
+if (jestExpect !== undefined) {
+  jestExpect.extend(matchers);
+} else {
+  console.error("Couldn't find Jest's global expect.");
+}

packages/cli/test/mocks/matchers/matchers.ts

@@ -0,0 +1 @@
+export * from './to-output';

packages/cli/test/mocks/matchers/to-output.ts

@@ -0,0 +1,67 @@
+import {
+  getLabelPrinter,
+  matcherHint,
+  printExpected,
+  printReceived,
+} from 'jest-matcher-utils';
+import type { Readable } from 'stream';
+import type { MatcherState } from 'expect';
+import type { MatcherHintOptions } from 'jest-matcher-utils';
+
+export async function toOutput(
+  this: MatcherState,
+  stream: Readable,
+  test: string,
+  timeout = 3000
+) {
+  const { isNot } = this;
+  const matcherName = 'toOutput';
+  const matcherHintOptions: MatcherHintOptions = {
+    isNot,
+    promise: this.promise,
+  };
+  return new Promise(resolve => {
+    let output = '';
+    let timeoutId = setTimeout(onTimeout, timeout);
+
+    const message = () => {
+      const labelExpected = 'Expected output';
+      const labelReceived = 'Received output';
+      const printLabel = getLabelPrinter(labelExpected, labelReceived);
+      const hint =
+        matcherHint(matcherName, 'stream', 'test', matcherHintOptions) + '\n\n';
+      return (
+        hint +
+        printLabel(labelExpected) +
+        (isNot ? 'not ' : '') +
+        printExpected(test) +
+        '\n' +
+        printLabel(labelReceived) +
+        (isNot ? '    ' : '') +
+        printReceived(output)
+      );
+    };
+
+    function onData(data: string) {
+      output += data;
+      if (output.includes(test)) {
+        cleanup();
+        resolve({ pass: true, message });
+      }
+    }
+
+    function onTimeout() {
+      cleanup();
+      resolve({ pass: false, message });
+    }
+
+    function cleanup() {
+      clearTimeout(timeoutId);
+      stream.removeListener('data', onData);
+      stream.pause();
+    }
+
+    stream.on('data', onData);
+    stream.resume();
+  });
+}