Publish Canary

- @vercel/build-utils@2.12.3-canary.44
 - vercel@23.1.3-canary.69
 - @vercel/client@10.2.3-canary.47
 - vercel-plugin-middleware@0.0.0-canary.21
 - vercel-plugin-go@1.0.0-canary.32
 - vercel-plugin-node@1.12.2-canary.36
 - vercel-plugin-python@1.0.0-canary.33
 - vercel-plugin-ruby@1.0.0-canary.32

errors/no-single-file-deployments.md

@@ -0,0 +1,9 @@
+# No Single File Deployments
+
+#### Why This Error Occurred
+
+You attempted to create a Vercel deployment where the input is a file, rather than a directory. Previously this was allowed, however this behavior has been removed as of Vercel CLI v24.0.0 because it exposed a potential security risk if the user accidentally created a deployment from a sensitive file.
+
+#### Possible Ways to Fix It
+
+- Run the `vercel deploy` command against a directory, instead of a file.

packages/build-utils/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@vercel/build-utils",
-  "version": "2.12.3-canary.39",
+  "version": "2.12.3-canary.44",
   "license": "MIT",
   "main": "./dist/index.js",
   "types": "./dist/index.d.js",

packages/build-utils/src/convert-runtime-to-plugin.ts

@@ -86,10 +86,10 @@ export function convertRuntimeToPlugin(
 
     const pages: { [key: string]: any } = {};
     const pluginName = packageName.replace('vercel-plugin-', '');
+    const outputPath = join(workPath, '.output');
 
     const traceDir = join(
-      workPath,
-      `.output`,
+      outputPath,
       `inputs`,
       // Legacy Runtimes can only provide API Routes, so that's
       // why we can use this prefix for all of them. Here, we have to
@@ -100,10 +100,7 @@ export function convertRuntimeToPlugin(
 
     await fs.ensureDir(traceDir);
 
-    let newPathsRuntime: Set<string> = new Set();
-
-    const entryDir = join('.output', 'server', 'pages');
-    const entryRoot = join(workPath, entryDir);
+    const entryRoot = join(outputPath, 'server', 'pages');
 
     for (const entrypoint of Object.keys(entrypoints)) {
       const { output } = await buildRuntime({
@@ -119,17 +116,6 @@ export function convertRuntimeToPlugin(
         },
       });
 
-      // Legacy Runtimes tend to pollute the `workPath` with compiled results,
-      // because the `workPath` used to be a place that was a place where they could
-      // just put anything, but nowadays it's the working directory of the `vercel build`
-      // command, which is the place where the developer keeps their source files,
-      // so we don't want to pollute this space unnecessarily. That means we have to clean
-      // up files that were created by the build, which is done further below.
-      const sourceFilesAfterBuild = await getSourceFiles(
-        workPath,
-        ignoreFilter
-      );
-
       // @ts-ignore This symbol is a private API
       const lambdaFiles: Files = output[FILES_SYMBOL];
 
@@ -145,6 +131,7 @@ export function convertRuntimeToPlugin(
 
       let handlerFileBase = output.handler;
       let handlerFile = lambdaFiles[handlerFileBase];
+      let handlerHasImport = false;
 
       const { handler } = output;
       const handlerMethod = handler.split('.').pop();
@@ -158,6 +145,7 @@ export function convertRuntimeToPlugin(
       if (!handlerFile) {
         handlerFileBase = handlerFileName + ext;
         handlerFile = lambdaFiles[handlerFileBase];
+        handlerHasImport = true;
       }
 
       if (!handlerFile || !handlerFile.fsPath) {
@@ -172,65 +160,89 @@ export function convertRuntimeToPlugin(
       const entryPath = join(dirname(entrypoint), entryBase);
       const entry = join(entryRoot, entryPath);
 
-      // We never want to link here, only copy, because the launcher
-      // file often has the same name for every entrypoint, which means that
-      // every build for every entrypoint overwrites the launcher of the previous
-      // one, so linking would end with a broken reference.
+      // Create the parent directory of the API Route that will be created
+      // for the current entrypoint inside of `.output/server/pages/api`.
       await fs.ensureDir(dirname(entry));
-      await fs.copy(handlerFile.fsPath, entry);
 
-      const newFilesEntrypoint: Array<string> = [];
-      const newDirectoriesEntrypoint: Array<string> = [];
+      // For compiled languages, the launcher file will be binary and therefore
+      // won't try to import a user-provided request handler (instead, it will
+      // contain it). But for interpreted languages, the launcher might try to
+      // load a user-provided request handler from the source file instead of bundling
+      // it, so we have to adjust the import statement inside the launcher to point
+      // to the respective source file. Previously, Legacy Runtimes simply expected
+      // the user-provided request-handler to be copied right next to the launcher,
+      // but with the new File System API, files won't be moved around unnecessarily.
+      if (handlerHasImport) {
+        const { fsPath } = handlerFile;
+        const encoding = 'utf-8';
 
-      const preBuildFiles = Object.values(sourceFilesPreBuild).map(file => {
-        return file.fsPath;
-      });
+        // This is the true directory of the user-provided request handler in the
+        // source files, so that's what we will use as an import path in the launcher.
+        const locationPrefix = relative(entry, outputPath);
 
-      // Generate a list of directories and files that weren't present
-      // before the entrypoint was processed by the Legacy Runtime, so
-      // that we can perform a cleanup later. We need to divide into files
-      // and directories because only cleaning up files might leave empty
-      // directories, and listing directories separately also speeds up the
-      // build because we can just delete them, which wipes all of their nested
-      // paths, instead of iterating through all files that should be deleted.
-      for (const file in sourceFilesAfterBuild) {
-        if (!sourceFilesPreBuild[file]) {
-          const path = sourceFilesAfterBuild[file].fsPath;
-          const dirPath = dirname(path);
+        let handlerContent = await fs.readFile(fsPath, encoding);
 
-          // If none of the files that were present before the entrypoint
-          // was processed are contained within the directory we're looking
-          // at right now, then we know it's a newly added directory
-          // and it can therefore be removed later on.
-          const isNewDir = !preBuildFiles.some(filePath => {
-            return dirname(filePath).startsWith(dirPath);
-          });
+        const importPaths = [
+          // This is the full entrypoint path, like `./api/test.py`. In our tests
+          // Python didn't support importing from a parent directory without using different
+          // code in the launcher that registers it as a location for modules and then changing
+          // the importing syntax, but continuing to import it like before seems to work. If
+          // other languages need this, we should consider excluding Python explicitly.
+          // `./${entrypoint}`,
 
-          // Check out the list of tracked directories that were
-          // newly added and see if one of them contains the path
-          // we're looking at.
-          const hasParentDir = newDirectoriesEntrypoint.some(dir => {
-            return path.startsWith(dir);
-          });
+          // This is the entrypoint path without extension, like `api/test`
+          entrypoint.slice(0, -ext.length),
+        ];
 
-          // If we have already tracked a directory that was newly
-          // added that sits above the file or directory that we're
-          // looking at, we don't need to add more entries to the list
-          // because when the parent will get removed in the future,
-          // all of its children (and therefore the path we're looking at)
-          // will automatically get removed anyways.
-          if (hasParentDir) {
-            continue;
-          }
+        // Generate a list of regular expressions that we can use for
+        // finding matches, but only allow matches if the import path is
+        // wrapped inside single (') or double quotes (").
+        const patterns = importPaths.map(path => {
+          // eslint-disable-next-line no-useless-escape
+          return new RegExp(`('|")(${path.replace(/\./g, '\\.')})('|")`, 'g');
+        });
 
-          if (isNewDir) {
-            newDirectoriesEntrypoint.push(dirPath);
-          } else {
-            newFilesEntrypoint.push(path);
+        let replacedMatch = null;
+
+        for (const pattern of patterns) {
+          const newContent = handlerContent.replace(
+            pattern,
+            (_, p1, p2, p3) => {
+              return `${p1}${join(locationPrefix, p2)}${p3}`;
+            }
+          );
+
+          if (newContent !== handlerContent) {
+            debug(
+              `Replaced "${pattern}" inside "${entry}" to ensure correct import of user-provided request handler`
+            );
+
+            handlerContent = newContent;
+            replacedMatch = true;
           }
         }
+
+        if (!replacedMatch) {
+          new Error(
+            `No replacable matches for "${importPaths[0]}" or "${importPaths[1]}" found in "${fsPath}"`
+          );
+        }
+
+        await fs.writeFile(entry, handlerContent, encoding);
+      } else {
+        await fs.copy(handlerFile.fsPath, entry);
       }
 
+      // Legacy Runtimes based on interpreted languages will create a new launcher file
+      // for every entrypoint, but they will create each one inside `workPath`, which means that
+      // the launcher for one entrypoint will overwrite the launcher provided for the previous
+      // entrypoint. That's why, above, we copy the file contents into the new destination (and
+      // optionally transform them along the way), instead of linking. We then also want to remove
+      // the copy origin right here, so that the `workPath` doesn't contain a useless launcher file
+      // once the build has finished running.
+      await fs.remove(handlerFile.fsPath);
+      debug(`Removed temporary file "${handlerFile.fsPath}"`);
+
       const nft = `${entry}.nft.json`;
 
       const json = JSON.stringify({
@@ -255,18 +267,8 @@ export function convertRuntimeToPlugin(
           .filter(Boolean),
       });
 
-      await fs.ensureDir(dirname(nft));
       await fs.writeFile(nft, json);
 
-      // Extend the list of directories and files that were created by the
-      // Legacy Runtime with the list of directories and files that were
-      // created for the entrypoint that was just processed above.
-      newPathsRuntime = new Set([
-        ...newPathsRuntime,
-        ...newFilesEntrypoint,
-        ...newDirectoriesEntrypoint,
-      ]);
-
       // Add an entry that will later on be added to the `functions-manifest.json`
       // file that is placed inside of the `.output` directory.
       pages[normalizePath(entryPath)] = {
@@ -283,20 +285,6 @@ export function convertRuntimeToPlugin(
       };
     }
 
-    // A list of all the files that were created by the Legacy Runtime,
-    // which we'd like to remove from the File System.
-    const toRemove = Array.from(newPathsRuntime).map(path => {
-      debug(`Removing ${path} as part of cleanup`);
-      return fs.remove(path);
-    });
-
-    // Once all the entrypoints have been processed, we'd like to
-    // remove all the files from `workPath` that originally weren't present
-    // before the Legacy Runtime began running, because the `workPath`
-    // is nowadays the directory in which the user keeps their source code, since
-    // we're no longer running separate parallel builds for every Legacy Runtime.
-    await Promise.all(toRemove);
-
     // Add any Serverless Functions that were exposed by the Legacy Runtime
     // to the `functions-manifest.json` file provided in `.output`.
     await updateFunctionsManifest({ workPath, pages });

packages/build-utils/src/detect-builders.ts

@@ -3,7 +3,13 @@ import { valid as validSemver } from 'semver';
 import { parse as parsePath, extname } from 'path';
 import { Route, Source } from '@vercel/routing-utils';
 import frameworkList, { Framework } from '@vercel/frameworks';
-import { PackageJson, Builder, Config, BuilderFunctions } from './types';
+import {
+  PackageJson,
+  Builder,
+  Config,
+  BuilderFunctions,
+  ProjectSettings,
+} from './types';
 import { isOfficialRuntime } from './';
 const slugToFramework = new Map<string | null, Framework>(
   frameworkList.map(f => [f.slug, f])
@@ -20,14 +26,7 @@ interface Options {
   tag?: 'canary' | 'latest' | string;
   functions?: BuilderFunctions;
   ignoreBuildScript?: boolean;
-  projectSettings?: {
-    framework?: string | null;
-    devCommand?: string | null;
-    installCommand?: string | null;
-    buildCommand?: string | null;
-    outputDirectory?: string | null;
-    createdAt?: number;
-  };
+  projectSettings?: ProjectSettings;
   cleanUrls?: boolean;
   trailingSlash?: boolean;
   featHandleMiss?: boolean;

packages/build-utils/src/detect-file-system-api.ts

@@ -0,0 +1,237 @@
+import semver from 'semver';
+import { isOfficialRuntime } from './';
+import type {
+  Builder,
+  BuilderFunctions,
+  PackageJson,
+  ProjectSettings,
+} from './types';
+
+interface Metadata {
+  plugins: string[];
+  hasDotOutput: boolean;
+  hasMiddleware: boolean;
+}
+
+const enableFileSystemApiFrameworks = new Set(['solidstart']);
+
+/**
+ * If the Deployment can be built with the new File System API,
+ * return the new Builder. Otherwise an "Exclusion Condition"
+ * was hit so return `null` builder with a `reason` for exclusion.
+ */
+export async function detectFileSystemAPI({
+  files,
+  projectSettings,
+  builders,
+  vercelConfig,
+  pkg,
+  tag,
+  enableFlag = false,
+}: {
+  files: { [relPath: string]: any };
+  projectSettings: ProjectSettings;
+  builders: Builder[];
+  vercelConfig:
+    | { builds?: Builder[]; functions?: BuilderFunctions }
+    | null
+    | undefined;
+  pkg: PackageJson | null | undefined;
+  tag: string | undefined;
+  enableFlag: boolean | undefined;
+}): Promise<
+  | { metadata: Metadata; fsApiBuilder: Builder; reason: null }
+  | { metadata: Metadata; fsApiBuilder: null; reason: string }
+> {
+  const framework = projectSettings.framework || '';
+  const deps = Object.assign({}, pkg?.dependencies, pkg?.devDependencies);
+  const plugins = Object.keys(deps).filter(dep =>
+    dep.startsWith('vercel-plugin-')
+  );
+  const hasDotOutput = Object.keys(files).some(file =>
+    file.startsWith('.output/')
+  );
+  const hasMiddleware = Boolean(
+    files['_middleware.js'] || files['_middleware.ts']
+  );
+
+  const metadata: Metadata = {
+    plugins,
+    hasDotOutput,
+    hasMiddleware,
+  };
+
+  const isEnabled =
+    enableFlag ||
+    hasMiddleware ||
+    hasDotOutput ||
+    enableFileSystemApiFrameworks.has(framework);
+  if (!isEnabled) {
+    return { metadata, fsApiBuilder: null, reason: 'Flag not enabled.' };
+  }
+
+  if (vercelConfig?.builds && vercelConfig.builds.length > 0) {
+    return {
+      metadata,
+      fsApiBuilder: null,
+      reason:
+        'Detected `builds` in vercel.json. Please remove it in favor of CLI plugins.',
+    };
+  }
+
+  if (Object.values(vercelConfig?.functions || {}).some(fn => !!fn.runtime)) {
+    return {
+      metadata,
+      fsApiBuilder: null,
+      reason:
+        'Detected `functions.runtime` in vercel.json. Please remove it in favor of CLI plugins.',
+    };
+  }
+
+  if (process.env.HUGO_VERSION) {
+    return {
+      metadata,
+      fsApiBuilder: null,
+      reason: 'Detected `HUGO_VERSION` environment variable. Please remove it.',
+    };
+  }
+
+  if (process.env.ZOLA_VERSION) {
+    return {
+      metadata,
+      fsApiBuilder: null,
+      reason: 'Detected `ZOLA_VERSION` environment variable. Please remove it.',
+    };
+  }
+
+  if (process.env.GUTENBERG_VERSION) {
+    return {
+      metadata,
+      fsApiBuilder: null,
+      reason:
+        'Detected `GUTENBERG_VERSION` environment variable. Please remove it.',
+    };
+  }
+
+  const invalidBuilder = builders.find(({ use }) => {
+    const valid =
+      isOfficialRuntime('go', use) ||
+      isOfficialRuntime('python', use) ||
+      isOfficialRuntime('ruby', use) ||
+      isOfficialRuntime('node', use) ||
+      isOfficialRuntime('next', use) ||
+      isOfficialRuntime('static', use) ||
+      isOfficialRuntime('static-build', use);
+    return !valid;
+  });
+
+  if (invalidBuilder) {
+    return {
+      metadata,
+      fsApiBuilder: null,
+      reason: `Detected \`${invalidBuilder.use}\` in vercel.json. Please remove it in favor of CLI plugins.`,
+    };
+  }
+
+  for (const lang of ['go', 'python', 'ruby']) {
+    for (const { use } of builders) {
+      const plugin = 'vercel-plugin-' + lang;
+      if (isOfficialRuntime(lang, use) && !deps[plugin]) {
+        return {
+          metadata,
+          fsApiBuilder: null,
+          reason: `Detected \`${lang}\` Serverless Function usage without plugin \`${plugin}\`. Please run \`npm i ${plugin}\`.`,
+        };
+      }
+    }
+  }
+
+  if (
+    framework === 'nuxtjs' ||
+    framework === 'sveltekit' ||
+    framework === 'redwoodjs'
+  ) {
+    return {
+      metadata,
+      fsApiBuilder: null,
+      reason: `Detected framework \`${framework}\` that only supports legacy File System API. Please contact the framework author.`,
+    };
+  }
+
+  if (framework === 'nextjs' && !hasDotOutput) {
+    // Use the old pipeline if a custom output directory was specified for Next.js
+    // because `vercel build` cannot ensure that the directory will be in the same
+    // location as `.output`, which can break imports (not just nft.json files).
+    if (projectSettings?.outputDirectory) {
+      return {
+        metadata,
+        fsApiBuilder: null,
+        reason: `Detected Next.js with Output Directory \`${projectSettings.outputDirectory}\` override. Please change it back to the default.`,
+      };
+    }
+    const nextVersion = deps['next'];
+    if (!nextVersion) {
+      return {
+        metadata,
+        fsApiBuilder: null,
+        reason: `Detected Next.js in Project Settings but missing \`next\` package.json dependencies. Please run \`npm i next\`.`,
+      };
+    }
+
+    // TODO: Read version from lockfile instead of package.json
+    if (nextVersion !== 'latest' && nextVersion !== 'canary') {
+      const fixedVersion = semver.valid(semver.coerce(nextVersion) || '');
+
+      if (!fixedVersion || !semver.gte(fixedVersion, '12.0.0')) {
+        return {
+          metadata,
+          fsApiBuilder: null,
+          reason: `Detected legacy Next.js version "${nextVersion}" in package.json. Please run \`npm i next@latest\` to upgrade.`,
+        };
+      }
+    }
+  }
+
+  if (!hasDotOutput) {
+    // TODO: Read version from lockfile instead of package.json
+    const vercelCliVersion = deps['vercel'];
+    if (
+      vercelCliVersion &&
+      vercelCliVersion !== 'latest' &&
+      vercelCliVersion !== 'canary'
+    ) {
+      const fixedVersion = semver.valid(semver.coerce(vercelCliVersion) || '');
+      // TODO: we might want to use '24.0.0' once its released
+      if (!fixedVersion || !semver.gte(fixedVersion, '23.1.3-canary.68')) {
+        return {
+          metadata,
+          fsApiBuilder: null,
+          reason: `Detected legacy Vercel CLI version "${vercelCliVersion}" in package.json. Please run \`npm i vercel@latest\` to upgrade.`,
+        };
+      }
+    }
+  }
+
+  const frontendBuilder = builders.find(
+    ({ use }) =>
+      isOfficialRuntime('next', use) ||
+      isOfficialRuntime('static', use) ||
+      isOfficialRuntime('static-build', use)
+  );
+  const config = frontendBuilder?.config || {};
+  const withTag = tag ? `@${tag}` : '';
+
+  const fsApiBuilder = {
+    use: `@vercelruntimes/file-system-api${withTag}`,
+    src: '**',
+    config: {
+      ...config,
+      fileSystemAPI: true,
+      framework: config.framework || framework || null,
+      projectSettings,
+      hasMiddleware,
+      hasDotOutput,
+    },
+  };
+  return { metadata, fsApiBuilder, reason: null };
+}

packages/build-utils/src/index.ts

@@ -81,6 +81,7 @@ export {
   detectApiDirectory,
   detectApiExtensions,
 } from './detect-builders';
+export { detectFileSystemAPI } from './detect-file-system-api';
 export { detectFramework } from './detect-framework';
 export { DetectorFilesystem } from './detectors/filesystem';
 export { readConfigFile } from './fs/read-config-file';

packages/build-utils/src/types.ts

@@ -29,7 +29,9 @@ export interface Config {
     | number
     | { [key: string]: string }
     | BuilderFunctions
-    | undefined;
+    | ProjectSettings
+    | undefined
+    | null;
   maxLambdaSize?: string;
   includeFiles?: string | string[];
   excludeFiles?: string | string[];
@@ -41,11 +43,12 @@ export interface Config {
   zeroConfig?: boolean;
   import?: { [key: string]: string };
   functions?: BuilderFunctions;
+  projectSettings?: ProjectSettings;
   outputDirectory?: string;
   installCommand?: string;
   buildCommand?: string;
   devCommand?: string;
-  framework?: string;
+  framework?: string | null;
   nodeVersion?: string;
 }
 
@@ -351,3 +354,17 @@ export interface BuilderFunctions {
     excludeFiles?: string;
   };
 }
+
+export interface ProjectSettings {
+  framework?: string | null;
+  devCommand?: string | null;
+  installCommand?: string | null;
+  buildCommand?: string | null;
+  outputDirectory?: string | null;
+  rootDirectory?: string | null;
+  createdAt?: number;
+  autoExposeSystemEnvs?: boolean;
+  sourceFilesOutsideRootDirectory?: boolean;
+  directoryListing?: boolean;
+  gitForkProtection?: boolean;
+}

packages/build-utils/test/unit.detect-file-system-api.test.ts

@@ -0,0 +1,445 @@
+import { detectFileSystemAPI } from '../src/detect-file-system-api';
+
+describe('Test `detectFileSystemAPI`', () => {
+  it('should error when builds in vercel.json', async () => {
+    const vercelConfig = {
+      builds: [{ use: '@vercel/node', src: 'api/**/*.js' }],
+    };
+    const files = {
+      'vercel.json': JSON.stringify(vercelConfig),
+      'api/foo.js': 'console.log("foo")',
+    };
+    const result = await detectFileSystemAPI({
+      files,
+      projectSettings: {},
+      builders: vercelConfig.builds,
+      vercelConfig,
+      pkg: null,
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason:
+        'Detected `builds` in vercel.json. Please remove it in favor of CLI plugins.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+  });
+
+  it('should error when functions.runtimes in vercel.json', async () => {
+    const vercelConfig = {
+      functions: {
+        'api/**/*.rs': {
+          runtime: 'vercel-rust@latest',
+        },
+      },
+    };
+    const files = {
+      'vercel.json': JSON.stringify(vercelConfig),
+      'api/foo.rs': 'println!("foo")',
+    };
+    const result = await detectFileSystemAPI({
+      files,
+      projectSettings: {},
+      builders: [],
+      vercelConfig,
+      pkg: null,
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason:
+        'Detected `functions.runtime` in vercel.json. Please remove it in favor of CLI plugins.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+  });
+
+  it('should error when HUGO_VERSION env var used', async () => {
+    process.env.HUGO_VERSION = 'v0.58.2';
+    const files = { 'foo.html': '<h1>Foo</h1>' };
+    const result = await detectFileSystemAPI({
+      files,
+      projectSettings: {},
+      builders: [],
+      vercelConfig: null,
+      pkg: null,
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason: 'Detected `HUGO_VERSION` environment variable. Please remove it.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+    delete process.env.HUGO_VERSION;
+  });
+
+  it('should error when ZOLA_VERSION env var used', async () => {
+    process.env.ZOLA_VERSION = 'v0.0.1';
+    const files = { 'foo.html': '<h1>Foo</h1>' };
+    const result = await detectFileSystemAPI({
+      files,
+      projectSettings: {},
+      builders: [],
+      vercelConfig: null,
+      pkg: null,
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason: 'Detected `ZOLA_VERSION` environment variable. Please remove it.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+    delete process.env.ZOLA_VERSION;
+  });
+
+  it('should error when GUTENBERG_VERSION env var used', async () => {
+    process.env.GUTENBERG_VERSION = 'v0.0.1';
+    const files = { 'foo.html': '<h1>Foo</h1>' };
+    const result = await detectFileSystemAPI({
+      files,
+      projectSettings: {},
+      builders: [],
+      vercelConfig: null,
+      pkg: null,
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason:
+        'Detected `GUTENBERG_VERSION` environment variable. Please remove it.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+    delete process.env.GUTENBERG_VERSION;
+  });
+
+  it('should error when Go detected without corresponding plugin', async () => {
+    const result = await detectFileSystemAPI({
+      files: { 'api/foo.go': 'print("foo")' },
+      projectSettings: {},
+      builders: [{ use: '@vercel/go', src: 'api/**/*.go' }],
+      vercelConfig: null,
+      pkg: null,
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason:
+        'Detected `go` Serverless Function usage without plugin `vercel-plugin-go`. Please run `npm i vercel-plugin-go`.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+  });
+
+  it('should error when Python detected without corresponding plugin', async () => {
+    const result = await detectFileSystemAPI({
+      files: { 'api/foo.py': 'print("foo")' },
+      projectSettings: {},
+      builders: [{ use: '@vercel/python', src: 'api/**/*.py' }],
+      vercelConfig: null,
+      pkg: null,
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason:
+        'Detected `python` Serverless Function usage without plugin `vercel-plugin-python`. Please run `npm i vercel-plugin-python`.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+  });
+
+  it('should error when Ruby detected without corresponding plugin', async () => {
+    const result = await detectFileSystemAPI({
+      files: { 'api/foo.rb': 'print("foo")' },
+      projectSettings: {},
+      builders: [{ use: '@vercel/ruby', src: 'api/**/*.rb' }],
+      vercelConfig: null,
+      pkg: null,
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason:
+        'Detected `ruby` Serverless Function usage without plugin `vercel-plugin-ruby`. Please run `npm i vercel-plugin-ruby`.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+  });
+
+  it('should succeed when Go detected with corresponding plugin', async () => {
+    const result = await detectFileSystemAPI({
+      files: { 'api/foo.go': 'print("foo")' },
+      projectSettings: {},
+      builders: [{ use: '@vercel/go', src: 'api/**/*.go' }],
+      vercelConfig: null,
+      pkg: { dependencies: { 'vercel-plugin-go': '^1.0.0' } },
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: {
+        use: '@vercelruntimes/file-system-api',
+        src: '**',
+        config: {
+          fileSystemAPI: true,
+          framework: null,
+          hasDotOutput: false,
+          hasMiddleware: false,
+          projectSettings: {},
+        },
+      },
+      reason: null,
+      metadata: {
+        hasDotOutput: false,
+        hasMiddleware: false,
+        plugins: ['vercel-plugin-go'],
+      },
+    });
+  });
+
+  it('should succeed when Python detected with corresponding plugin', async () => {
+    const result = await detectFileSystemAPI({
+      files: { 'api/foo.py': 'print("foo")' },
+      projectSettings: {},
+      builders: [{ use: '@vercel/python', src: 'api/**/*.py' }],
+      vercelConfig: null,
+      pkg: { dependencies: { 'vercel-plugin-python': '^1.0.0' } },
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: {
+        use: '@vercelruntimes/file-system-api',
+        src: '**',
+        config: {
+          fileSystemAPI: true,
+          framework: null,
+          hasDotOutput: false,
+          hasMiddleware: false,
+          projectSettings: {},
+        },
+      },
+      reason: null,
+      metadata: {
+        hasDotOutput: false,
+        hasMiddleware: false,
+        plugins: ['vercel-plugin-python'],
+      },
+    });
+  });
+
+  it('should succeed when Ruby detected with corresponding plugin', async () => {
+    const result = await detectFileSystemAPI({
+      files: { 'api/foo.rb': 'print("foo")' },
+      projectSettings: {},
+      builders: [{ use: '@vercel/ruby', src: 'api/**/*.rb' }],
+      vercelConfig: null,
+      pkg: { dependencies: { 'vercel-plugin-ruby': '^1.0.0' } },
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: {
+        use: '@vercelruntimes/file-system-api',
+        src: '**',
+        config: {
+          fileSystemAPI: true,
+          framework: null,
+          hasDotOutput: false,
+          hasMiddleware: false,
+          projectSettings: {},
+        },
+      },
+      reason: null,
+      metadata: {
+        hasDotOutput: false,
+        hasMiddleware: false,
+        plugins: ['vercel-plugin-ruby'],
+      },
+    });
+  });
+
+  it('should error when framework is nuxtjs', async () => {
+    const result = await detectFileSystemAPI({
+      files: { 'api/foo.js': 'console.log("foo")' },
+      projectSettings: { framework: 'nuxtjs' },
+      builders: [{ use: '@vercel/node', src: 'api/**/*.js' }],
+      vercelConfig: null,
+      pkg: null,
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason:
+        'Detected framework `nuxtjs` that only supports legacy File System API. Please contact the framework author.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+  });
+
+  it('should error when framework is sveltekit', async () => {
+    const result = await detectFileSystemAPI({
+      files: { 'api/foo.js': 'console.log("foo")' },
+      projectSettings: { framework: 'sveltekit' },
+      builders: [{ use: '@vercel/node', src: 'api/**/*.js' }],
+      vercelConfig: null,
+      pkg: null,
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason:
+        'Detected framework `sveltekit` that only supports legacy File System API. Please contact the framework author.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+  });
+
+  it('should error when framework is redwoodjs', async () => {
+    const result = await detectFileSystemAPI({
+      files: { 'api/foo.js': 'console.log("foo")' },
+      projectSettings: { framework: 'redwoodjs' },
+      builders: [{ use: '@vercel/node', src: 'api/**/*.js' }],
+      vercelConfig: null,
+      pkg: null,
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason:
+        'Detected framework `redwoodjs` that only supports legacy File System API. Please contact the framework author.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+  });
+
+  it('should error when framework is nextjs and has output dir', async () => {
+    const result = await detectFileSystemAPI({
+      files: { 'pages/foo.js': 'console.log("foo")' },
+      projectSettings: { framework: 'nextjs', outputDirectory: 'dist' },
+      builders: [{ use: '@vercel/next', src: 'package.json' }],
+      vercelConfig: null,
+      pkg: { dependencies: { next: '^12.0.0' } },
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason:
+        'Detected Next.js with Output Directory `dist` override. Please change it back to the default.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+  });
+
+  it('should error when framework is nextjs but missing from dependencies', async () => {
+    const result = await detectFileSystemAPI({
+      files: { 'pages/foo.js': 'console.log("foo")' },
+      projectSettings: { framework: 'nextjs' },
+      builders: [{ use: '@vercel/next', src: 'package.json' }],
+      vercelConfig: null,
+      pkg: { dependencies: { 'not-next': '^12.0.0' } },
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason:
+        'Detected Next.js in Project Settings but missing `next` package.json dependencies. Please run `npm i next`.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+  });
+
+  it('should error when framework is nextjs but dependency is older version', async () => {
+    const result = await detectFileSystemAPI({
+      files: { 'pages/foo.js': 'console.log("foo")' },
+      projectSettings: { framework: 'nextjs' },
+      builders: [{ use: '@vercel/next', src: 'package.json' }],
+      vercelConfig: null,
+      pkg: { dependencies: { next: '^9.0.0' } },
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason:
+        'Detected legacy Next.js version "^9.0.0" in package.json. Please run `npm i next@latest` to upgrade.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+  });
+
+  it('should error when vercel cli is older version', async () => {
+    const result = await detectFileSystemAPI({
+      files: { 'pages/foo.js': 'console.log("foo")' },
+      projectSettings: { framework: 'nextjs' },
+      builders: [{ use: '@vercel/next', src: 'package.json' }],
+      vercelConfig: null,
+      pkg: { dependencies: { next: '^12.1.0', vercel: '^23.1.1' } },
+      tag: '',
+      enableFlag: true,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: null,
+      reason:
+        'Detected legacy Vercel CLI version "^23.1.1" in package.json. Please run `npm i vercel@latest` to upgrade.',
+      metadata: { hasDotOutput: false, hasMiddleware: false, plugins: [] },
+    });
+  });
+
+  it('should succeed when middleware detected', async () => {
+    const result = await detectFileSystemAPI({
+      files: { '_middleware.js': 'print("foo")' },
+      projectSettings: {},
+      builders: [{ use: '@vercel/static-build', src: 'package.json' }],
+      vercelConfig: null,
+      pkg: null,
+      tag: '',
+      enableFlag: false,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: {
+        use: '@vercelruntimes/file-system-api',
+        src: '**',
+        config: {
+          fileSystemAPI: true,
+          framework: null,
+          hasDotOutput: false,
+          hasMiddleware: true,
+          projectSettings: {},
+        },
+      },
+      reason: null,
+      metadata: { hasDotOutput: false, hasMiddleware: true, plugins: [] },
+    });
+  });
+
+  it('should succeed when .output detected', async () => {
+    const result = await detectFileSystemAPI({
+      files: { '.output/routes-manifest.json': '{}' },
+      projectSettings: { framework: 'remix' },
+      builders: [{ use: '@vercel/static-build', src: 'package.json' }],
+      vercelConfig: null,
+      pkg: null,
+      tag: '',
+      enableFlag: false,
+    });
+    expect(result).toEqual({
+      fsApiBuilder: {
+        use: '@vercelruntimes/file-system-api',
+        src: '**',
+        config: {
+          fileSystemAPI: true,
+          framework: 'remix',
+          hasDotOutput: true,
+          hasMiddleware: false,
+          projectSettings: { framework: 'remix' },
+        },
+      },
+      reason: null,
+      metadata: { hasDotOutput: true, hasMiddleware: false, plugins: [] },
+    });
+  });
+});

packages/cli/README.md

@@ -34,7 +34,7 @@ Finally, [connect your Git repository to Vercel](https://vercel.com/docs/git) an
 
 ## Documentation
 
-For details on how to use Vercel CLI, check out our [documentation](https://vercel.com/docs).
+For details on how to use Vercel CLI, check out our [documentation](https://vercel.com/docs/cli).
 
 ## Local Development
 

packages/cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "vercel",
-  "version": "23.1.3-canary.62",
+  "version": "23.1.3-canary.69",
   "preferGlobal": true,
   "license": "Apache-2.0",
   "description": "The command-line interface for Vercel",
@@ -43,14 +43,14 @@
     "node": ">= 12"
   },
   "dependencies": {
-    "@vercel/build-utils": "2.12.3-canary.39",
+    "@vercel/build-utils": "2.12.3-canary.44",
     "@vercel/go": "1.2.4-canary.4",
     "@vercel/node": "1.12.2-canary.7",
-    "@vercel/python": "2.1.2-canary.1",
+    "@vercel/python": "2.1.2-canary.2",
     "@vercel/ruby": "1.2.10-canary.0",
     "update-notifier": "4.1.0",
-    "vercel-plugin-middleware": "0.0.0-canary.15",
-    "vercel-plugin-node": "1.12.2-canary.31"
+    "vercel-plugin-middleware": "0.0.0-canary.21",
+    "vercel-plugin-node": "1.12.2-canary.36"
   },
   "devDependencies": {
     "@next/env": "11.1.2",
@@ -90,6 +90,7 @@
     "@types/update-notifier": "5.1.0",
     "@types/which": "1.3.2",
     "@types/write-json-file": "2.2.1",
+    "@vercel/client": "10.2.3-canary.47",
     "@vercel/frameworks": "0.5.1-canary.17",
     "@vercel/ncc": "0.24.0",
     "@vercel/nft": "0.17.0",

packages/cli/src/commands/build.ts

@@ -6,6 +6,9 @@ import {
   scanParentDirs,
   spawnAsync,
   glob as buildUtilsGlob,
+  detectFileSystemAPI,
+  detectBuilders,
+  PackageJson,
 } from '@vercel/build-utils';
 import { nodeFileTrace } from '@vercel/nft';
 import Sema from 'async-sema';
@@ -19,6 +22,7 @@ import pluralize from 'pluralize';
 import Client from '../util/client';
 import { VercelConfig } from '../util/dev/types';
 import { emoji, prependEmoji } from '../util/emoji';
+import { CantParseJSONFile } from '../util/errors-ts';
 import getArgs from '../util/get-args';
 import handleError from '../util/handle-error';
 import confirm from '../util/input/confirm';
@@ -32,6 +36,7 @@ import { loadCliPlugins } from '../util/plugins';
 import { findFramework } from '../util/projects/find-framework';
 import { VERCEL_DIR } from '../util/projects/link';
 import { readProjectSettings } from '../util/projects/project-settings';
+import readJSONFile from '../util/read-json-file';
 import pull from './pull';
 
 const sema = new Sema(16, {
@@ -146,6 +151,36 @@ export default async function main(client: Client) {
 
   process.chdir(cwd);
 
+  const pkg = await readJSONFile<PackageJson>('./package.json');
+  if (pkg instanceof CantParseJSONFile) {
+    throw pkg;
+  }
+  const vercelConfig = await readJSONFile<VercelConfig>('./vercel.json');
+  if (vercelConfig instanceof CantParseJSONFile) {
+    throw vercelConfig;
+  }
+
+  if (!process.env.NOW_BUILDER) {
+    // This validation is only necessary when
+    // a user runs `vercel build` locally.
+    const globFiles = await buildUtilsGlob('**', { cwd });
+    const zeroConfig = await detectBuilders(Object.keys(globFiles), pkg);
+    const { reason } = await detectFileSystemAPI({
+      files: globFiles,
+      projectSettings: project.settings,
+      builders: zeroConfig.builders || [],
+      pkg,
+      vercelConfig,
+      tag: '',
+      enableFlag: true,
+    });
+
+    if (reason) {
+      client.output.error(`${cmd(`${getPkgName()} build`)} failed: ${reason}`);
+      return 1;
+    }
+  }
+
   const framework = findFramework(project.settings.framework);
   // If this is undefined, we bail. If it is null, then findFramework should return "Other",
   // so this should really never happen, but just in case....

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

@@ -166,8 +166,8 @@ export default async (client: Client) => {
     return pathValidation.exitCode;
   }
 
-  const { isFile, path } = pathValidation;
-  const autoConfirm = argv['--confirm'] || isFile;
+  const { path } = pathValidation;
+  const autoConfirm = argv['--confirm'];
 
   // deprecate --name
   if (argv['--name']) {
@@ -192,7 +192,7 @@ export default async (client: Client) => {
 
   let newProjectName = null;
   let rootDirectory = project ? project.rootDirectory : null;
-  let sourceFilesOutsideRootDirectory = true;
+  let sourceFilesOutsideRootDirectory: boolean | undefined = true;
 
   if (status === 'not_linked') {
     const shouldStartSetup =
@@ -229,8 +229,7 @@ export default async (client: Client) => {
     // user input.
     const detectedProjectName = getProjectName({
       argv,
-      nowConfig: localConfig || {},
-      isFile,
+      nowConfig: localConfig,
       paths,
     });
 
@@ -447,9 +446,9 @@ export default async (client: Client) => {
       forceNew: argv['--force'],
       withCache: argv['--with-cache'],
       prebuilt: argv['--prebuilt'],
+      rootDirectory,
       quiet,
       wantsPublic: argv['--public'] || localConfig.public,
-      isFile,
       type: null,
       nowConfig: localConfig,
       regions,
@@ -471,7 +470,7 @@ export default async (client: Client) => {
       [sourcePath],
       createArgs,
       org,
-      !project && !isFile,
+      !project,
       path
     );
 
@@ -654,8 +653,7 @@ export default async (client: Client) => {
     client,
     deployment,
     deployStamp,
-    !argv['--no-clipboard'],
-    isFile
+    !argv['--no-clipboard']
   );
 };
 
@@ -790,8 +788,7 @@ const printDeploymentStatus = async (
     };
   },
   deployStamp: () => string,
-  isClipboardEnabled: boolean,
-  isFile: boolean
+  isClipboardEnabled: boolean
 ) => {
   indications = indications || [];
   const isProdDeployment = target === 'production';
@@ -813,7 +810,7 @@ const printDeploymentStatus = async (
     // print preview/production url
     let previewUrl: string;
     let isWildcard: boolean;
-    if (!isFile && Array.isArray(aliasList) && aliasList.length > 0) {
+    if (Array.isArray(aliasList) && aliasList.length > 0) {
       const previewUrlInfo = await getPreferredPreviewURL(client, aliasList);
       if (previewUrlInfo) {
         isWildcard = previewUrlInfo.isWildcard;

packages/cli/src/types.ts

@@ -1,3 +1,5 @@
+export type ProjectSettings = import('@vercel/build-utils').ProjectSettings;
+
 export type Primitive =
   | bigint
   | boolean
@@ -239,16 +241,6 @@ export interface ProjectEnvVariable {
   gitBranch?: string;
 }
 
-export interface ProjectSettings {
-  framework?: string | null;
-  devCommand?: string | null;
-  buildCommand?: string | null;
-  outputDirectory?: string | null;
-  rootDirectory?: string | null;
-  autoExposeSystemEnvs?: boolean;
-  directoryListing?: boolean;
-}
-
 export interface Project extends ProjectSettings {
   id: string;
   name: string;
@@ -260,8 +252,6 @@ export interface Project extends ProjectSettings {
   framework?: string | null;
   rootDirectory?: string | null;
   latestDeployments?: Partial<Deployment>[];
-  autoExposeSystemEnvs?: boolean;
-  sourceFilesOutsideRootDirectory: boolean;
 }
 
 export interface Org {

packages/cli/src/util/config/read-config.ts

@@ -6,14 +6,14 @@ import getLocalConfigPath from './local-path';
 
 export default async function readConfig(dir: string) {
   const pkgFilePath = getLocalConfigPath(join(process.cwd(), dir));
-  const result = await readJSONFile(pkgFilePath);
+  const result = await readJSONFile<VercelConfig>(pkgFilePath);
 
   if (result instanceof CantParseJSONFile) {
     return result;
   }
 
   if (result) {
-    return result as VercelConfig;
+    return result;
   }
 
   return null;

packages/cli/src/util/deploy/process-deployment.ts

@@ -52,6 +52,7 @@ export default async function processDeployment({
   isSettingUpProject: boolean;
   skipAutoDetectionConfirmation?: boolean;
   cwd?: string;
+  rootDirectory?: string;
 }) {
   let {
     now,
@@ -64,6 +65,7 @@ export default async function processDeployment({
     nowConfig,
     quiet,
     prebuilt,
+    rootDirectory,
   } = args;
 
   const { debug } = output;
@@ -86,6 +88,7 @@ export default async function processDeployment({
     force,
     withCache,
     prebuilt,
+    rootDirectory,
     skipAutoDetectionConfirmation,
   };
 

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

@@ -40,6 +40,7 @@ import {
   detectApiExtensions,
   spawnCommand,
   isOfficialRuntime,
+  detectFileSystemAPI,
 } from '@vercel/build-utils';
 import frameworkList from '@vercel/frameworks';
 
@@ -599,6 +600,32 @@ export default class DevServer {
         );
       }
 
+      const { reason, metadata } = await detectFileSystemAPI({
+        files,
+        builders: builders || [],
+        projectSettings: projectSettings || this.projectSettings || {},
+        vercelConfig,
+        pkg,
+        tag: '',
+        enableFlag: true,
+      });
+
+      if (reason) {
+        if (metadata.hasMiddleware) {
+          this.output.error(
+            `Detected middleware usage which requires the latest API. ${reason}`
+          );
+          await this.exit();
+        } else if (metadata.plugins.length > 0) {
+          this.output.error(
+            `Detected CLI plugins which requires the latest API. ${reason}`
+          );
+          await this.exit();
+        } else {
+          this.output.warn(`Unable to use latest API. ${reason}`);
+        }
+      }
+
       if (builders) {
         if (this.devCommand) {
           builders = builders.filter(filterFrontendBuilds);

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

@@ -39,12 +39,12 @@ export default async function getConfig(
     output.debug(
       `Found config in provided --local-config path ${localFilePath}`
     );
-    const localConfig = await readJSONFile(localFilePath);
+    const localConfig = await readJSONFile<VercelConfig>(localFilePath);
     if (localConfig instanceof CantParseJSONFile) {
       return localConfig;
     }
     if (localConfig !== null) {
-      config = localConfig as VercelConfig;
+      config = localConfig;
       config[fileNameSymbol] = configFile;
       return config;
     }
@@ -54,8 +54,8 @@ export default async function getConfig(
   const vercelFilePath = path.resolve(localPath, 'vercel.json');
   const nowFilePath = path.resolve(localPath, 'now.json');
   const [vercelConfig, nowConfig] = await Promise.all([
-    readJSONFile(vercelFilePath),
-    readJSONFile(nowFilePath),
+    readJSONFile<VercelConfig>(vercelFilePath),
+    readJSONFile<VercelConfig>(nowFilePath),
   ]);
   if (vercelConfig instanceof CantParseJSONFile) {
     return vercelConfig;
@@ -68,13 +68,13 @@ export default async function getConfig(
   }
   if (vercelConfig !== null) {
     output.debug(`Found config in file "${vercelFilePath}"`);
-    config = vercelConfig as VercelConfig;
+    config = vercelConfig;
     config[fileNameSymbol] = 'vercel.json';
     return config;
   }
   if (nowConfig !== null) {
     output.debug(`Found config in file "${nowFilePath}"`);
-    config = nowConfig as VercelConfig;
+    config = nowConfig;
     config[fileNameSymbol] = 'now.json';
     return config;
   }

packages/cli/src/util/get-project-name.ts

@@ -4,14 +4,12 @@ import { VercelConfig } from '@vercel/client';
 export interface GetProjectNameOptions {
   argv: { '--name'?: string };
   nowConfig?: VercelConfig;
-  isFile?: boolean;
   paths?: string[];
 }
 
 export default function getProjectName({
   argv,
   nowConfig = {},
-  isFile = false,
   paths = [],
 }: GetProjectNameOptions) {
   const nameCli = argv['--name'];
@@ -24,10 +22,6 @@ export default function getProjectName({
     return nowConfig.name;
   }
 
-  if (isFile || paths.length > 1) {
-    return 'files';
-  }
-
   // Otherwise, use the name of the directory
   return basename(paths[0] || '');
 }

packages/cli/src/util/index.ts

@@ -30,13 +30,13 @@ export interface NowOptions {
 export interface CreateOptions {
   // Legacy
   nowConfig?: VercelConfig;
-  isFile?: boolean;
 
   // Latest
   name: string;
   project?: string;
   wantsPublic: boolean;
   prebuilt?: boolean;
+  rootDirectory?: string;
   meta: Dictionary<string>;
   regions?: string[];
   quiet?: boolean;
@@ -113,6 +113,7 @@ export default class Now extends EventEmitter {
       name,
       project,
       prebuilt = false,
+      rootDirectory,
       wantsPublic,
       meta,
       regions,
@@ -168,6 +169,7 @@ export default class Now extends EventEmitter {
       skipAutoDetectionConfirmation,
       cwd,
       prebuilt,
+      rootDirectory,
     });
 
     if (deployment && deployment.warnings) {

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

@@ -11,7 +11,7 @@ export default async function inputProject(
   client: Client,
   org: Org,
   detectedProjectName: string,
-  autoConfirm: boolean
+  autoConfirm = false
 ): Promise<Project | string> {
   const { output } = client;
   const slugifiedName = slugify(detectedProjectName);

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

@@ -7,7 +7,7 @@ import { validateRootDirectory } from '../validate-paths';
 export async function inputRootDirectory(
   cwd: string,
   output: Output,
-  autoConfirm: boolean
+  autoConfirm = false
 ) {
   if (autoConfirm) {
     return null;

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

@@ -158,7 +158,6 @@ export default async function setupAndLink(
         withCache: undefined,
         quiet,
         wantsPublic: localConfig?.public || false,
-        isFile,
         nowConfig: localConfig,
         regions: undefined,
         meta: {},
@@ -179,7 +178,7 @@ export default async function setupAndLink(
         [sourcePath],
         createArgs,
         org,
-        !isFile,
+        true,
         path
       );
 

packages/cli/src/util/read-json-file.ts

@@ -1,9 +1,9 @@
 import fs from 'fs-extra';
 import { CantParseJSONFile } from './errors-ts';
 
-export default async function readJSONFile(
+export default async function readJSONFile<T>(
   file: string
-): Promise<Object | null | CantParseJSONFile> {
+): Promise<T | null | CantParseJSONFile> {
   const content = await readFileSafe(file);
   if (content === null) {
     return content;

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

@@ -4,7 +4,6 @@ import { Output } from './output';
 import chalk from 'chalk';
 import { homedir } from 'os';
 import confirm from './input/confirm';
-import { prependEmoji, emoji } from './emoji';
 import toHumanPath from './humanize-path';
 
 const stat = promisify(lstatRaw);
@@ -54,10 +53,7 @@ export async function validateRootDirectory(
 export default async function validatePaths(
   output: Output,
   paths: string[]
-): Promise<
-  | { valid: true; path: string; isFile: boolean }
-  | { valid: false; exitCode: number }
-> {
+): Promise<{ valid: true; path: string } | { valid: false; exitCode: number }> {
   // can't deploy more than 1 path
   if (paths.length > 1) {
     output.print(`${chalk.red('Error!')} Can't deploy more than one path.\n`);
@@ -78,14 +74,12 @@ export default async function validatePaths(
     return { valid: false, exitCode: 1 };
   }
 
-  const isFile = pathStat && !pathStat.isDirectory();
-  if (isFile) {
-    output.print(
-      `${prependEmoji(
-        'Deploying files with Vercel is deprecated (https://vercel.link/faq-deploy-file)',
-        emoji('warning')
-      )}\n`
-    );
+  if (!pathStat.isDirectory()) {
+    output.prettyError({
+      message: 'Support for single file deployments has been removed.',
+      link: 'https://vercel.link/no-single-file-deployments',
+    });
+    return { valid: false, exitCode: 1 };
   }
 
   // ask confirmation if the directory is home
@@ -101,5 +95,5 @@ export default async function validatePaths(
     }
   }
 
-  return { valid: true, path, isFile };
+  return { valid: true, path };
 }

packages/cli/test/commands/deploy.test.ts

@@ -0,0 +1,60 @@
+import { join } from 'path';
+import { fileNameSymbol } from '@vercel/client';
+import { client } from '../mocks/client';
+import deploy from '../../src/commands/deploy';
+
+describe('deploy', () => {
+  it('should reject deploying a single file', async () => {
+    client.setArgv('deploy', __filename);
+    const exitCode = await deploy(client);
+    expect(exitCode).toEqual(1);
+    expect(client.outputBuffer).toEqual(
+      `Error! Support for single file deployments has been removed.\nLearn More: https://vercel.link/no-single-file-deployments\n`
+    );
+  });
+
+  it('should reject deploying multiple files', async () => {
+    client.setArgv('deploy', __filename, join(__dirname, 'inspect.test.ts'));
+    const exitCode = await deploy(client);
+    expect(exitCode).toEqual(1);
+    expect(client.outputBuffer).toEqual(
+      `Error! Can't deploy more than one path.\n`
+    );
+  });
+
+  it('should reject deploying a directory that does not exist', async () => {
+    client.setArgv('deploy', 'does-not-exists');
+    const exitCode = await deploy(client);
+    expect(exitCode).toEqual(1);
+    expect(client.outputBuffer).toEqual(
+      `Error! The specified file or directory "does-not-exists" does not exist.\n`
+    );
+  });
+
+  it('should reject deploying "version: 1"', async () => {
+    client.setArgv('deploy');
+    client.localConfig = {
+      [fileNameSymbol]: 'vercel.json',
+      version: 1,
+    };
+    const exitCode = await deploy(client);
+    expect(exitCode).toEqual(1);
+    expect(client.outputBuffer).toEqual(
+      'Error! The value of the `version` property within vercel.json can only be `2`.\n'
+    );
+  });
+
+  it('should reject deploying "version: {}"', async () => {
+    client.setArgv('deploy');
+    client.localConfig = {
+      [fileNameSymbol]: 'vercel.json',
+      // @ts-ignore
+      version: {},
+    };
+    const exitCode = await deploy(client);
+    expect(exitCode).toEqual(1);
+    expect(client.outputBuffer).toEqual(
+      'Error! The `version` property inside your vercel.json file must be a number.\n'
+    );
+  });
+});

packages/cli/test/integration.js

@@ -1913,59 +1913,6 @@ test('create a production deployment', async t => {
   t.is(deployment.target, 'production', JSON.stringify(deployment, null, 2));
 });
 
-test('deploying a file should not show prompts and display deprecation', async t => {
-  const file = fixture('static-single-file/first.png');
-
-  const output = await execute([file], {
-    reject: false,
-  });
-
-  const { stdout, stderr, exitCode } = output;
-
-  // Ensure the exit code is right
-  t.is(exitCode, 0, formatOutput(output));
-  t.true(stderr.includes('Deploying files with Vercel is deprecated'));
-
-  // Ensure `.vercel` was not created
-  t.is(
-    await exists(path.join(path.dirname(file), '.vercel')),
-    false,
-    '.vercel should not exists'
-  );
-
-  // Test if the output is really a URL
-  const { href, host } = new URL(stdout);
-  t.is(host.split('-')[0], 'files');
-
-  // Send a test request to the deployment
-  const response = await fetch(href);
-  const contentType = response.headers.get('content-type');
-
-  t.is(contentType, 'image/png');
-  t.deepEqual(await readFile(file), await response.buffer());
-});
-
-test('deploying more than 1 path should fail', async t => {
-  const file1 = fixture('static-multiple-files/first.png');
-  const file2 = fixture('static-multiple-files/second.png');
-
-  const { stdout, stderr, exitCode } = await execa(
-    binaryPath,
-    [file1, file2, '--public', '--name', session, ...defaultArgs, '--confirm'],
-    {
-      reject: false,
-    }
-  );
-
-  console.log(stderr);
-  console.log(stdout);
-  console.log(exitCode);
-
-  // Ensure the exit code is right
-  t.is(exitCode, 1);
-  t.true(stderr.trim().endsWith(`Can't deploy more than one path.`));
-});
-
 test('use build-env', async t => {
   const directory = fixture('build-env');
 

packages/cli/test/util/get-project-name.test.ts

@@ -10,7 +10,7 @@ describe('getProjectName', () => {
     expect(project).toEqual('abc');
   });
 
-  it('should work with now.json', () => {
+  it('should work with `vercel.json` config', () => {
     const project = getProjectName({
       argv: {},
       nowConfig: { name: 'abc' },
@@ -18,24 +18,6 @@ describe('getProjectName', () => {
     expect(project).toEqual('abc');
   });
 
-  it('should work with a file', () => {
-    const project = getProjectName({
-      argv: {},
-      nowConfig: {},
-      isFile: true,
-    });
-    expect(project).toEqual('files');
-  });
-
-  it('should work with a multiple files', () => {
-    const project = getProjectName({
-      argv: {},
-      nowConfig: {},
-      paths: ['/tmp/aa/abc.png', '/tmp/aa/bbc.png'],
-    });
-    expect(project).toEqual('files');
-  });
-
   it('should work with a directory', () => {
     const project = getProjectName({
       argv: {},

packages/client/.gitignore

@@ -6,3 +6,5 @@ node_modules
 !tests/fixtures/nowignore/node_modules
 !tests/fixtures/vercelignore-allow-nodemodules/node_modules
 !tests/fixtures/vercelignore-allow-nodemodules/sub/node_modules
+!tests/fixtures/file-system-api/.output
+!tests/fixtures/file-system-api-root-directory/**/.output

packages/client/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@vercel/client",
-  "version": "10.2.3-canary.40",
+  "version": "10.2.3-canary.47",
   "main": "dist/index.js",
   "typings": "dist/index.d.ts",
   "homepage": "https://vercel.com",
@@ -40,7 +40,7 @@
     ]
   },
   "dependencies": {
-    "@vercel/build-utils": "2.12.3-canary.39",
+    "@vercel/build-utils": "2.12.3-canary.44",
     "@zeit/fetch": "5.2.0",
     "async-retry": "1.2.3",
     "async-sema": "3.0.0",

packages/client/src/create-deployment.ts

@@ -1,12 +1,12 @@
 import { lstatSync } from 'fs-extra';
 
 import { relative, isAbsolute } from 'path';
-import hashes, { mapToObject } from './utils/hashes';
+import { hashes, mapToObject, resolveNftJsonFiles } from './utils/hashes';
 import { upload } from './upload';
 import { buildFileTree, createDebug, parseVercelConfig } from './utils';
 import { DeploymentError } from './errors';
 import {
-  NowConfig,
+  VercelConfig,
   VercelClientOptions,
   DeploymentOptions,
   DeploymentEventType,
@@ -16,7 +16,7 @@ export default function buildCreateDeployment() {
   return async function* createDeployment(
     clientOptions: VercelClientOptions,
     deploymentOptions: DeploymentOptions = {},
-    nowConfig: NowConfig = {}
+    nowConfig: VercelConfig = {}
   ): AsyncIterableIterator<{ type: DeploymentEventType; payload: any }> {
     const { path } = clientOptions;
 
@@ -74,12 +74,7 @@ export default function buildCreateDeployment() {
       debug(`Provided 'path' is a single file`);
     }
 
-    let { fileList } = await buildFileTree(
-      path,
-      clientOptions.isDirectory,
-      debug,
-      clientOptions.prebuilt
-    );
+    let { fileList } = await buildFileTree(path, clientOptions, debug);
 
     let configPath: string | undefined;
     if (!nowConfig) {
@@ -114,7 +109,11 @@ export default function buildCreateDeployment() {
       };
     }
 
-    const files = await hashes(fileList);
+    const hashedFileMap = await hashes(fileList);
+    const nftFileList = clientOptions.prebuilt
+      ? await resolveNftJsonFiles(hashedFileMap)
+      : [];
+    const files = await hashes(nftFileList, hashedFileMap);
 
     debug(`Yielding a 'hashes-calculated' event with ${files.size} hashes`);
     yield { type: 'hashes-calculated', payload: mapToObject(files) };

packages/client/src/types.ts

@@ -1,4 +1,8 @@
-import { Builder, BuilderFunctions } from '@vercel/build-utils';
+import {
+  Builder,
+  BuilderFunctions,
+  ProjectSettings,
+} from '@vercel/build-utils';
 import { Header, Route, Redirect, Rewrite } from '@vercel/routing-utils';
 
 export { DeploymentEventType } from './utils';
@@ -15,6 +19,7 @@ export interface VercelClientOptions {
   apiUrl?: string;
   force?: boolean;
   prebuilt?: boolean;
+  rootDirectory?: string;
   withCache?: boolean;
   userAgent?: string;
   defaultName?: string;
@@ -123,12 +128,7 @@ export interface VercelConfig {
   scope?: string;
   alias?: string | string[];
   regions?: string[];
-  projectSettings?: {
-    devCommand?: string | null;
-    buildCommand?: string | null;
-    outputDirectory?: string | null;
-    framework?: string | null;
-  };
+  projectSettings?: ProjectSettings;
 }
 
 /**
@@ -154,9 +154,5 @@ export interface DeploymentOptions {
   name?: string;
   public?: boolean;
   meta?: Dictionary<string>;
-  projectSettings?: {
-    devCommand?: string | null;
-    buildCommand?: string | null;
-    outputDirectory?: string | null;
-  };
+  projectSettings?: ProjectSettings;
 }

packages/client/src/utils/hashes.ts

@@ -1,6 +1,7 @@
 import { createHash } from 'crypto';
 import fs from 'fs-extra';
 import { Sema } from 'async-sema';
+import { join, dirname } from 'path';
 
 export interface DeploymentFile {
   names: string[];
@@ -15,9 +16,7 @@ export interface DeploymentFile {
  * @return {String} hex digest
  */
 function hash(buf: Buffer): string {
-  return createHash('sha1')
-    .update(buf)
-    .digest('hex');
+  return createHash('sha1').update(buf).digest('hex');
 }
 
 /**
@@ -39,34 +38,68 @@ export const mapToObject = (
 /**
  * Computes hashes for the contents of each file given.
  *
- * @param {Array} of {String} full paths
- * @return {Map}
+ * @param files - absolute file paths
+ * @param map - optional map of files to append
+ * @return Map of hash digest to file object
  */
-async function hashes(files: string[]): Promise<Map<string, DeploymentFile>> {
-  const map = new Map<string, DeploymentFile>();
+export async function hashes(
+  files: string[],
+  map = new Map<string, DeploymentFile>()
+): Promise<Map<string, DeploymentFile>> {
   const semaphore = new Sema(100);
 
   await Promise.all(
-    files.map(
-      async (name: string): Promise<void> => {
-        await semaphore.acquire();
-        const data = await fs.readFile(name);
-        const { mode } = await fs.stat(name);
+    files.map(async (name: string): Promise<void> => {
+      await semaphore.acquire();
+      const data = await fs.readFile(name);
+      const { mode } = await fs.stat(name);
 
-        const h = hash(data);
-        const entry = map.get(h);
+      const h = hash(data);
+      const entry = map.get(h);
 
-        if (entry) {
-          entry.names.push(name);
-        } else {
-          map.set(h, { names: [name], data, mode });
-        }
-
-        semaphore.release();
+      if (entry) {
+        const names = new Set(entry.names);
+        names.add(name);
+        entry.names = [...names];
+      } else {
+        map.set(h, { names: [name], data, mode });
       }
-    )
+
+      semaphore.release();
+    })
   );
   return map;
 }
 
-export default hashes;
+export async function resolveNftJsonFiles(
+  hashedFiles: Map<string, DeploymentFile>
+): Promise<string[]> {
+  const semaphore = new Sema(100);
+  const existingFiles = Array.from(hashedFiles.values());
+  const resolvedFiles = new Set<string>();
+
+  await Promise.all(
+    existingFiles.map(async file => {
+      await semaphore.acquire();
+      const fsPath = file.names[0];
+      if (fsPath.endsWith('.nft.json')) {
+        const json = file.data.toString('utf8');
+        const { version, files } = JSON.parse(json) as {
+          version: number;
+          files: string[] | { input: string; output: string }[];
+        };
+        if (version === 1 || version === 2) {
+          for (let f of files) {
+            const relPath = typeof f === 'string' ? f : f.input;
+            resolvedFiles.add(join(dirname(fsPath), relPath));
+          }
+        } else {
+          console.error(`Invalid nft.json version: ${version}`);
+        }
+      }
+      semaphore.release();
+    })
+  );
+
+  return Array.from(resolvedFiles);
+}

packages/client/src/utils/index.ts

@@ -1,7 +1,7 @@
 import { DeploymentFile } from './hashes';
 import { FetchOptions } from '@zeit/fetch';
 import { nodeFetch, zeitFetch } from './fetch';
-import { join, sep, relative } from 'path';
+import { join, sep, relative, posix } from 'path';
 import { URL } from 'url';
 import ignore from 'ignore';
 type Ignore = ReturnType<typeof ignore>;
@@ -81,13 +81,16 @@ const maybeRead = async function <T>(path: string, default_: T) {
 
 export async function buildFileTree(
   path: string | string[],
-  isDirectory: boolean,
-  debug: Debug,
-  prebuilt?: boolean
+  {
+    isDirectory,
+    prebuilt,
+    rootDirectory,
+  }: Pick<VercelClientOptions, 'isDirectory' | 'prebuilt' | 'rootDirectory'>,
+  debug: Debug
 ): Promise<{ fileList: string[]; ignoreList: string[] }> {
   const ignoreList: string[] = [];
   let fileList: string[];
-  let { ig, ignores } = await getVercelIgnore(path, prebuilt);
+  let { ig, ignores } = await getVercelIgnore(path, prebuilt, rootDirectory);
 
   debug(`Found ${ignores.length} rules in .vercelignore`);
   debug('Building file tree...');
@@ -119,37 +122,50 @@ export async function buildFileTree(
 
 export async function getVercelIgnore(
   cwd: string | string[],
-  prebuilt?: boolean
+  prebuilt?: boolean,
+  rootDirectory?: string
 ): Promise<{ ig: Ignore; ignores: string[] }> {
-  const ignores: string[] = prebuilt
-    ? ['*', '!.output', '!.output/**']
-    : [
-        '.hg',
-        '.git',
-        '.gitmodules',
-        '.svn',
-        '.cache',
-        '.next',
-        '.now',
-        '.vercel',
-        '.npmignore',
-        '.dockerignore',
-        '.gitignore',
-        '.*.swp',
-        '.DS_Store',
-        '.wafpicke-*',
-        '.lock-wscript',
-        '.env.local',
-        '.env.*.local',
-        '.venv',
-        'npm-debug.log',
-        'config.gypi',
-        'node_modules',
-        '__pycache__',
-        'venv',
-        'CVS',
-        '.output',
-      ];
+  let ignores: string[] = [];
+
+  const outputDir = posix.join(rootDirectory || '', '.output');
+
+  if (prebuilt) {
+    ignores.push('*');
+    const parts = outputDir.split('/');
+    parts.forEach((_, i) => {
+      const level = parts.slice(0, i + 1).join('/');
+      ignores.push(`!${level}`);
+    });
+    ignores.push(`!${outputDir}/**`);
+  } else {
+    ignores = [
+      '.hg',
+      '.git',
+      '.gitmodules',
+      '.svn',
+      '.cache',
+      '.next',
+      '.now',
+      '.vercel',
+      '.npmignore',
+      '.dockerignore',
+      '.gitignore',
+      '.*.swp',
+      '.DS_Store',
+      '.wafpicke-*',
+      '.lock-wscript',
+      '.env.local',
+      '.env.*.local',
+      '.venv',
+      'npm-debug.log',
+      'config.gypi',
+      'node_modules',
+      '__pycache__',
+      'venv',
+      'CVS',
+      `.output`,
+    ];
+  }
   const cwds = Array.isArray(cwd) ? cwd : [cwd];
 
   const files = await Promise.all(
@@ -250,39 +266,31 @@ export const prepareFiles = (
   files: Map<string, DeploymentFile>,
   clientOptions: VercelClientOptions
 ): PreparedFile[] => {
-  const preparedFiles = [...files.keys()].reduce(
-    (acc: PreparedFile[], sha: string): PreparedFile[] => {
-      const next = [...acc];
+  const preparedFiles: PreparedFile[] = [];
+  for (const [sha, file] of files) {
+    for (const name of file.names) {
+      let fileName: string;
 
-      const file = files.get(sha) as DeploymentFile;
-
-      for (const name of file.names) {
-        let fileName: string;
-
-        if (clientOptions.isDirectory) {
-          // Directory
-          fileName =
-            typeof clientOptions.path === 'string'
-              ? relative(clientOptions.path, name)
-              : name;
-        } else {
-          // Array of files or single file
-          const segments = name.split(sep);
-          fileName = segments[segments.length - 1];
-        }
-
-        next.push({
-          file: isWin ? fileName.replace(/\\/g, '/') : fileName,
-          size: file.data.byteLength || file.data.length,
-          mode: file.mode,
-          sha,
-        });
+      if (clientOptions.isDirectory) {
+        // Directory
+        fileName =
+          typeof clientOptions.path === 'string'
+            ? relative(clientOptions.path, name)
+            : name;
+      } else {
+        // Array of files or single file
+        const segments = name.split(sep);
+        fileName = segments[segments.length - 1];
       }
 
-      return next;
-    },
-    []
-  );
+      preparedFiles.push({
+        file: isWin ? fileName.replace(/\\/g, '/') : fileName,
+        size: file.data.byteLength || file.data.length,
+        mode: file.mode,
+        sha,
+      });
+    }
+  }
 
   return preparedFiles;
 };

packages/client/tests/fixtures/file-system-api-root-directory/foo.txt

@@ -0,0 +1 @@
+foo

packages/client/tests/fixtures/file-system-api-root-directory/root/.output/baz.txt

@@ -0,0 +1 @@
+baz

packages/client/tests/fixtures/file-system-api-root-directory/root/.output/sub/qux.txt

@@ -0,0 +1 @@
+qux

packages/client/tests/fixtures/file-system-api-root-directory/root/bar.txt

@@ -0,0 +1 @@
+bar

packages/client/tests/fixtures/file-system-api-root-directory/someother/.output/baz.txt

@@ -0,0 +1 @@
+baz

packages/client/tests/fixtures/file-system-api-root-directory/someother/.output/sub/qux.txt

@@ -0,0 +1 @@
+qux

packages/client/tests/fixtures/file-system-api-root-directory/someother/bar.txt

@@ -0,0 +1 @@
+bar

packages/client/tests/fixtures/file-system-api/.output/baz.txt

@@ -0,0 +1 @@
+baz

packages/client/tests/fixtures/file-system-api/.output/sub/qux.txt

@@ -0,0 +1 @@
+qux

packages/client/tests/fixtures/file-system-api/foo.txt

@@ -0,0 +1 @@
+foo

packages/client/tests/fixtures/file-system-api/sub/bar.txt

@@ -0,0 +1 @@
+bar

packages/client/tests/tsconfig.json

@@ -0,0 +1,4 @@
+{
+  "extends": "../tsconfig.json",
+  "include": ["*.test.ts"]
+}

packages/client/tests/unit.utils.test.ts

@@ -17,7 +17,11 @@ const toAbsolutePaths = (cwd: string, files: string[]) =>
 describe('buildFileTree()', () => {
   it('should exclude files using `.nowignore` blocklist', async () => {
     const cwd = fixture('nowignore');
-    const { fileList, ignoreList } = await buildFileTree(cwd, true, noop);
+    const { fileList, ignoreList } = await buildFileTree(
+      cwd,
+      { isDirectory: true },
+      noop
+    );
 
     const expectedFileList = toAbsolutePaths(cwd, ['.nowignore', 'index.txt']);
     expect(normalizeWindowsPaths(expectedFileList).sort()).toEqual(
@@ -36,7 +40,11 @@ describe('buildFileTree()', () => {
 
   it('should include the node_modules using `.vercelignore` allowlist', async () => {
     const cwd = fixture('vercelignore-allow-nodemodules');
-    const { fileList, ignoreList } = await buildFileTree(cwd, true, noop);
+    const { fileList, ignoreList } = await buildFileTree(
+      cwd,
+      { isDirectory: true },
+      noop
+    );
 
     const expected = toAbsolutePaths(cwd, [
       'node_modules/one.txt',
@@ -54,4 +62,90 @@ describe('buildFileTree()', () => {
       normalizeWindowsPaths(ignoreList).sort()
     );
   });
+
+  it('should find root files but ignore .output files when prebuilt=false', async () => {
+    const cwd = fixture('file-system-api');
+    const { fileList, ignoreList } = await buildFileTree(
+      cwd,
+      { isDirectory: true, prebuilt: false },
+      noop
+    );
+
+    const expectedFileList = toAbsolutePaths(cwd, ['foo.txt', 'sub/bar.txt']);
+    expect(normalizeWindowsPaths(expectedFileList).sort()).toEqual(
+      normalizeWindowsPaths(fileList).sort()
+    );
+
+    const expectedIgnoreList = ['.output'];
+    expect(normalizeWindowsPaths(expectedIgnoreList).sort()).toEqual(
+      normalizeWindowsPaths(ignoreList).sort()
+    );
+  });
+
+  it('should find .output files but ignore other files when prebuilt=true', async () => {
+    const cwd = fixture('file-system-api');
+    const { fileList, ignoreList } = await buildFileTree(
+      cwd,
+      { isDirectory: true, prebuilt: true },
+      noop
+    );
+
+    const expectedFileList = toAbsolutePaths(cwd, [
+      '.output/baz.txt',
+      '.output/sub/qux.txt',
+    ]);
+    expect(normalizeWindowsPaths(expectedFileList).sort()).toEqual(
+      normalizeWindowsPaths(fileList).sort()
+    );
+
+    const expectedIgnoreList = ['foo.txt', 'sub'];
+    expect(normalizeWindowsPaths(expectedIgnoreList).sort()).toEqual(
+      normalizeWindowsPaths(ignoreList).sort()
+    );
+  });
+
+  it('should find root files but ignore all .output files when prebuilt=false and rootDirectory=root', async () => {
+    const cwd = fixture('file-system-api-root-directory');
+    const { fileList, ignoreList } = await buildFileTree(
+      cwd,
+      { isDirectory: true, prebuilt: false, rootDirectory: 'root' },
+      noop
+    );
+
+    const expectedFileList = toAbsolutePaths(cwd, [
+      'foo.txt',
+      'root/bar.txt',
+      'someother/bar.txt',
+    ]);
+    expect(normalizeWindowsPaths(expectedFileList).sort()).toEqual(
+      normalizeWindowsPaths(fileList).sort()
+    );
+
+    const expectedIgnoreList = ['root/.output', 'someother/.output'];
+    expect(normalizeWindowsPaths(expectedIgnoreList).sort()).toEqual(
+      normalizeWindowsPaths(ignoreList).sort()
+    );
+  });
+
+  it('should find root/.output files but ignore other files when prebuilt=true and rootDirectory=root', async () => {
+    const cwd = fixture('file-system-api-root-directory');
+    const { fileList, ignoreList } = await buildFileTree(
+      cwd,
+      { isDirectory: true, prebuilt: true, rootDirectory: 'root' },
+      noop
+    );
+
+    const expectedFileList = toAbsolutePaths(cwd, [
+      'root/.output/baz.txt',
+      'root/.output/sub/qux.txt',
+    ]);
+    expect(normalizeWindowsPaths(expectedFileList).sort()).toEqual(
+      normalizeWindowsPaths(fileList).sort()
+    );
+
+    const expectedIgnoreList = ['foo.txt', 'root/bar.txt', 'someother'];
+    expect(normalizeWindowsPaths(expectedIgnoreList).sort()).toEqual(
+      normalizeWindowsPaths(ignoreList).sort()
+    );
+  });
 });

packages/middleware/package.json

@@ -1,6 +1,6 @@
 {
   "name": "vercel-plugin-middleware",
-  "version": "0.0.0-canary.15",
+  "version": "0.0.0-canary.21",
   "license": "MIT",
   "main": "./dist/index",
   "homepage": "",
@@ -30,7 +30,7 @@
     "@types/node-fetch": "^2",
     "@types/ua-parser-js": "0.7.36",
     "@types/uuid": "8.3.1",
-    "@vercel/build-utils": "2.12.3-canary.39",
+    "@vercel/build-utils": "2.12.3-canary.44",
     "@vercel/ncc": "0.24.0",
     "cookie": "0.4.1",
     "formdata-node": "4.3.1",

packages/middleware/src/esbuild-plugins.ts

@@ -0,0 +1,52 @@
+import path from 'path';
+import * as esbuild from 'esbuild';
+
+const processInjectFile = `
+// envOverride is passed by esbuild plugin
+const env = envOverride
+function cwd() {
+    return '/'
+}
+function chdir(dir) {
+    throw new Error('process.chdir is not supported')
+}
+export const process = {
+  argv: [],
+  env,
+  chdir,
+  cwd,
+};
+`;
+
+export function nodeProcessPolyfillPlugin({ env = {} } = {}): esbuild.Plugin {
+  return {
+    name: 'node-process-polyfill',
+    setup({ initialOptions, onResolve, onLoad }) {
+      onResolve({ filter: /_virtual-process-polyfill_\.js/ }, ({ path }) => {
+        return {
+          path,
+          sideEffects: false,
+        };
+      });
+
+      onLoad({ filter: /_virtual-process-polyfill_\.js/ }, () => {
+        const contents = `const envOverride = ${JSON.stringify(
+          env
+        )};\n${processInjectFile}`;
+        return {
+          loader: 'js',
+          contents,
+        };
+      });
+
+      const polyfills = [
+        path.resolve(__dirname, '_virtual-process-polyfill_.js'),
+      ];
+      if (initialOptions.inject) {
+        initialOptions.inject.push(...polyfills);
+      } else {
+        initialOptions.inject = [...polyfills];
+      }
+    },
+  };
+}

packages/middleware/src/index.ts

@@ -17,6 +17,7 @@ import {
   UrlWithParsedQuery,
 } from 'url';
 import { toNodeHeaders } from './websandbox/utils';
+import { nodeProcessPolyfillPlugin } from './esbuild-plugins';
 
 const glob = util.promisify(libGlob);
 const SUPPORTED_EXTENSIONS = ['.js', '.ts'];
@@ -80,6 +81,7 @@ export async function build({ workPath }: { workPath: string }) {
       banner: {
         js: '"use strict";',
       },
+      plugins: [nodeProcessPolyfillPlugin({ env: process.env })],
       format: 'cjs',
     });
     // Create `_ENTRIES` wrapper

packages/middleware/test/__snapshots__/build.test.ts.snap

@@ -15,6 +15,6 @@ Object {
       "sortingIndex": 1,
     },
   },
-  "version": 1,
+  "version": 2,
 }
 `;

packages/middleware/test/build.test.ts

@@ -63,6 +63,32 @@ describe('build()', () => {
     ).toEqual('1');
   });
 
+  it('should build simple middleware with env vars', async () => {
+    const expectedEnvVar = 'expected-env-var';
+    const fixture = join(__dirname, 'fixtures/env');
+    process.env.ENV_VAR_SHOULD_BE_DEFINED = expectedEnvVar;
+    await build({
+      workPath: fixture,
+    });
+    // env var should be inlined in the output
+    delete process.env.ENV_VAR_SHOULD_BE_DEFINED;
+
+    const outputFile = join(fixture, '.output/server/pages/_middleware.js');
+    expect(await fsp.stat(outputFile)).toBeTruthy();
+
+    require(outputFile);
+    //@ts-ignore
+    const middleware = global._ENTRIES['middleware_pages/_middleware'].default;
+    expect(typeof middleware).toStrictEqual('function');
+    const handledResponse = await middleware({
+      request: {},
+    });
+    expect(String(handledResponse.response.body)).toEqual(expectedEnvVar);
+    expect(
+      (handledResponse.response as Response).headers.get('x-middleware-next')
+    ).toEqual(null);
+  });
+
   it('should create a middleware that runs in strict mode', async () => {
     const { middleware } = await setupFixture('use-strict');
     const response = await middleware({

packages/middleware/test/fixtures/env/_middleware.js

@@ -0,0 +1,3 @@
+export default req => {
+  return new Response(process.env.ENV_VAR_SHOULD_BE_DEFINED);
+};

packages/plugin-go/package.json

@@ -1,7 +1,7 @@
 {
   "private": false,
   "name": "vercel-plugin-go",
-  "version": "1.0.0-canary.27",
+  "version": "1.0.0-canary.32",
   "main": "dist/index.js",
   "license": "MIT",
   "files": [
@@ -17,7 +17,7 @@
     "prepublishOnly": "tsc"
   },
   "dependencies": {
-    "@vercel/build-utils": "2.12.3-canary.39",
+    "@vercel/build-utils": "2.12.3-canary.44",
     "@vercel/go": "1.2.4-canary.4"
   },
   "devDependencies": {

packages/plugin-node/package.json

@@ -1,6 +1,6 @@
 {
   "name": "vercel-plugin-node",
-  "version": "1.12.2-canary.31",
+  "version": "1.12.2-canary.36",
   "license": "MIT",
   "main": "./dist/index",
   "homepage": "https://vercel.com/docs/runtimes#official-runtimes/node-js",
@@ -34,7 +34,7 @@
     "@types/node-fetch": "2",
     "@types/test-listen": "1.1.0",
     "@types/yazl": "2.4.2",
-    "@vercel/build-utils": "2.12.3-canary.39",
+    "@vercel/build-utils": "2.12.3-canary.44",
     "@vercel/fun": "1.0.3",
     "@vercel/ncc": "0.24.0",
     "@vercel/nft": "0.14.0",

packages/plugin-python/package.json

@@ -1,7 +1,7 @@
 {
   "private": false,
   "name": "vercel-plugin-python",
-  "version": "1.0.0-canary.28",
+  "version": "1.0.0-canary.33",
   "main": "dist/index.js",
   "license": "MIT",
   "files": [
@@ -17,8 +17,8 @@
     "prepublishOnly": "tsc"
   },
   "dependencies": {
-    "@vercel/build-utils": "2.12.3-canary.39",
-    "@vercel/python": "2.1.2-canary.1"
+    "@vercel/build-utils": "2.12.3-canary.44",
+    "@vercel/python": "2.1.2-canary.2"
   },
   "devDependencies": {
     "@types/node": "*",

packages/plugin-ruby/package.json

@@ -1,7 +1,7 @@
 {
   "private": false,
   "name": "vercel-plugin-ruby",
-  "version": "1.0.0-canary.27",
+  "version": "1.0.0-canary.32",
   "main": "dist/index.js",
   "license": "MIT",
   "files": [
@@ -17,7 +17,7 @@
     "prepublishOnly": "tsc"
   },
   "dependencies": {
-    "@vercel/build-utils": "2.12.3-canary.39",
+    "@vercel/build-utils": "2.12.3-canary.44",
     "@vercel/ruby": "1.2.10-canary.0"
   },
   "devDependencies": {

packages/python/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@vercel/python",
-  "version": "2.1.2-canary.1",
+  "version": "2.1.2-canary.2",
   "main": "./dist/index.js",
   "license": "MIT",
   "homepage": "https://vercel.com/docs/runtimes#official-runtimes/python",

packages/python/src/install.ts

@@ -1,4 +1,3 @@
-import { relative, basename } from 'path';
 import execa from 'execa';
 import { Meta, debug } from '@vercel/build-utils';
 
@@ -136,17 +135,10 @@ export async function installRequirementsFile({
   meta,
   args = [],
 }: InstallRequirementsFileArg) {
-  const fileAtRoot = relative(workPath, filePath) === basename(filePath);
-
-  // If the `requirements.txt` file is located in the Root Directory of the project and
-  // the new File System API is used (`avoidTopLevelInstall`), the Install Command
-  // will have already installed its dependencies, so we don't need to do it again.
-  if (meta.avoidTopLevelInstall && fileAtRoot) {
-    debug(
-      `Skipping requirements file installation, already installed by Install Command`
-    );
-    return;
-  }
+  // The Vercel platform already handles `requirements.txt` for frontend projects,
+  // but the installation logic there is different, because it seems to install all
+  // of the dependencies globally, whereas, for this Runtime, we want it to happen only
+  // locally, so we'll run a separate installation.
 
   if (
     meta.isDev &&