[build-utils][cli][go][node][ruby][static-build] Explicitly set PATH when copying env vars (#8532)

On Windows 10 and 11 machines, environment variables are not case sensitive. The system PATH is actually defined as `process.env.Path`, however Node.js kindly handles the case sensitivity and will automatically return the system path when specifying `process.env.PATH`.

When we clone the environment variables via `{ ...process.env }`, we lose the automatic resolving of `Path` to `PATH`. To fix this, we need to explicitly copy the `PATH`.

#### Tests

- [x] The code changed/added as part of this PR has been covered with tests
- [x] All tests pass locally with `yarn test-unit`

#### Code Review

- [ ] This PR has a concise title and thorough description useful to a reviewer
- [ ] Issue from task tracker has a link to this PR

packages/build-utils/src/clone-env.ts

@@ -0,0 +1,29 @@
+import type { Env } from './types';
+
+const { hasOwnProperty } = Object.prototype;
+
+/**
+ * Clones zero or more objects into a single new object while ensuring that the
+ * `PATH` environment variable is defined when the `PATH` or `Path` environment
+ * variables are defined.
+ *
+ * @param {Object} [...envs] Objects and/or `process.env` to clone and merge
+ * @returns {Object} The new object
+ */
+export function cloneEnv(...envs: (Env | undefined)[]): Env {
+  return envs.reduce((obj: Env, env) => {
+    if (env === undefined || env === null) {
+      return obj;
+    }
+
+    // the system path is called `Path` on Windows and Node.js will
+    // automatically return the system path when accessing `PATH`,
+    // however we lose this proxied value when we destructure and
+    // thus we must explicitly copy it
+    if (hasOwnProperty.call(env, 'PATH') || hasOwnProperty.call(env, 'Path')) {
+      obj.PATH = env.PATH;
+    }
+
+    return Object.assign(obj, env);
+  }, {});
+}

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

@@ -11,6 +11,7 @@ import { NowBuildError } from '../errors';
 import { Meta, PackageJson, NodeVersion, Config } from '../types';
 import { getSupportedNodeVersion, getLatestNodeVersion } from './node-version';
 import { readConfigFile } from './read-config-file';
+import { cloneEnv } from '../clone-env';
 
 // Only allow one `runNpmInstall()` invocation to run concurrently
 const runNpmInstallSema = new Sema(1);
@@ -217,7 +218,7 @@ export function getSpawnOptions(
   nodeVersion: NodeVersion
 ): SpawnOptions {
   const opts = {
-    env: { ...process.env },
+    env: cloneEnv(process.env),
   };
 
   if (!meta.isDev) {
@@ -449,7 +450,7 @@ export async function runNpmInstall(
     debug(`Installing to ${destPath}`);
 
     const opts: SpawnOptionsExtended = { cwd: destPath, ...spawnOpts };
-    const env = opts.env ? { ...opts.env } : { ...process.env };
+    const env = cloneEnv(opts.env || process.env);
     delete env.NODE_ENV;
     opts.env = getEnvForPackageManager({
       cliType,
@@ -591,10 +592,7 @@ export async function runPackageJsonScript(
       cliType,
       lockfileVersion,
       nodeVersion: undefined,
-      env: {
-        ...process.env,
-        ...spawnOpts?.env,
-      },
+      env: cloneEnv(process.env, spawnOpts?.env),
     }),
   };
 

packages/build-utils/src/index.ts

@@ -41,6 +41,7 @@ import debug from './debug';
 import getIgnoreFilter from './get-ignore-filter';
 import { getPlatformEnv } from './get-platform-env';
 import { getPrefixedEnvVars } from './get-prefixed-env-vars';
+import { cloneEnv } from './clone-env';
 
 export {
   FileBlob,
@@ -84,6 +85,7 @@ export {
   getLambdaOptionsFromFunction,
   scanParentDirs,
   getIgnoreFilter,
+  cloneEnv,
 };
 
 export { EdgeFunction } from './edge-function';

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

@@ -0,0 +1,120 @@
+import { cloneEnv } from '../src';
+
+it('should clone env with Path', () => {
+  expect(
+    cloneEnv(
+      new Proxy(
+        {
+          foo: 'bar',
+          Path: 'baz',
+        },
+        {
+          get(target: typeof process.env, prop: string) {
+            if (prop === 'PATH') {
+              return target.PATH ?? target.Path;
+            }
+            return target[prop];
+          },
+        }
+      )
+    )
+  ).toEqual({
+    foo: 'bar',
+    Path: 'baz',
+    PATH: 'baz',
+  });
+});
+
+it('should clone env with PATH', () => {
+  expect(
+    cloneEnv({
+      foo: 'bar',
+      PATH: 'baz',
+    })
+  ).toEqual({
+    foo: 'bar',
+    PATH: 'baz',
+  });
+});
+
+it('should clone and merge multiple env objects', () => {
+  // note: this also tests the last object doesn't overwrite `PATH` with
+  // `undefined`
+  expect(
+    cloneEnv(
+      {
+        foo: 'bar',
+      },
+      {
+        PATH: 'baz',
+      },
+      {
+        baz: 'wiz',
+      }
+    )
+  ).toEqual({
+    foo: 'bar',
+    PATH: 'baz',
+    baz: 'wiz',
+  });
+});
+
+it('should clone the actual process.env object', () => {
+  expect(cloneEnv(process.env).PATH).toEqual(process.env.PATH);
+});
+
+it('should overwrite PATH with last value', () => {
+  expect(
+    cloneEnv(
+      new Proxy(
+        {
+          Path: 'foo',
+        },
+        {
+          get(target: typeof process.env, prop: string) {
+            if (prop === 'PATH') {
+              return target.PATH ?? target.Path;
+            }
+            return target[prop];
+          },
+        }
+      ),
+      {
+        PATH: 'bar',
+      },
+      {
+        PATH: undefined,
+      }
+    )
+  ).toEqual({
+    Path: 'foo',
+    PATH: undefined,
+  });
+});
+
+it('should handle process.env at any argument position', () => {
+  expect(
+    cloneEnv(
+      {
+        foo: 'bar',
+      },
+      new Proxy(
+        {
+          Path: 'baz',
+        },
+        {
+          get(target: typeof process.env, prop: string) {
+            if (prop === 'PATH') {
+              return target.PATH ?? target.Path;
+            }
+            return target[prop];
+          },
+        }
+      )
+    )
+  ).toEqual({
+    foo: 'bar',
+    Path: 'baz',
+    PATH: 'baz',
+  });
+});

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

@@ -31,6 +31,7 @@ import {
 } from '@vercel/routing-utils';
 import {
   Builder,
+  cloneEnv,
   Env,
   StartDevServerResult,
   FileFsRef,
@@ -2222,18 +2223,22 @@ export default class DevServer {
 
     const port = await getPort();
 
-    const env: Env = {
-      // Because of child process 'pipe' below, isTTY will be false.
-      // Most frameworks use `chalk`/`supports-color` so we enable it anyway.
-      FORCE_COLOR: process.stdout.isTTY ? '1' : '0',
-      // Prevent framework dev servers from automatically opening a web
-      // browser window, since it will not be the port that `vc dev`
-      // is listening on and thus will be missing Vercel features.
-      BROWSER: 'none',
-      ...process.env,
-      ...this.envConfigs.allEnv,
-      PORT: `${port}`,
-    };
+    const env: Env = cloneEnv(
+      {
+        // Because of child process 'pipe' below, isTTY will be false.
+        // Most frameworks use `chalk`/`supports-color` so we enable it anyway.
+        FORCE_COLOR: process.stdout.isTTY ? '1' : '0',
+        // Prevent framework dev servers from automatically opening a web
+        // browser window, since it will not be the port that `vc dev`
+        // is listening on and thus will be missing Vercel features.
+        BROWSER: 'none',
+      },
+      process.env,
+      this.envConfigs.allEnv,
+      {
+        PORT: `${port}`,
+      }
+    );
 
     // This is necesary so that the dev command in the Project
     // will work cross-platform (especially Windows).

packages/go/index.ts

@@ -27,6 +27,7 @@ import {
   getWriteableDirectory,
   shouldServe,
   debug,
+  cloneEnv,
 } from '@vercel/build-utils';
 
 const TMP = tmpdir();
@@ -694,11 +695,9 @@ Learn more: https://vercel.com/docs/runtimes#official-runtimes/go`
     `vercel-dev-port-${Math.random().toString(32).substring(2)}`
   );
 
-  const env: typeof process.env = {
-    ...process.env,
-    ...meta.env,
+  const env = cloneEnv(process.env, meta.env, {
     VERCEL_DEV_PORT_FILE: portFile,
-  };
+  });
 
   const tmpRelative = `.${sep}${entrypointDir}`;
   const child = spawn('go', ['run', tmpRelative], {

packages/node/src/index.ts

@@ -36,6 +36,7 @@ import {
   debug,
   isSymbolicLink,
   walkParentDirs,
+  cloneEnv,
 } from '@vercel/build-utils';
 import type {
   File,
@@ -525,15 +526,13 @@ export const startDevServer: StartDevServer = async opts => {
   const child = fork(devServerPath, [], {
     cwd: workPath,
     execArgv: [],
-    env: {
-      ...process.env,
-      ...meta.env,
+    env: cloneEnv(process.env, meta.env, {
       VERCEL_DEV_ENTRYPOINT: entrypoint,
       VERCEL_DEV_TSCONFIG: projectTsConfig || '',
       VERCEL_DEV_IS_ESM: isEsm ? '1' : undefined,
       VERCEL_DEV_CONFIG: JSON.stringify(config),
       VERCEL_DEV_BUILD_ENV: JSON.stringify(meta.buildEnv || {}),
-    },
+    }),
   });
 
   const { pid } = child;

packages/ruby/index.ts

@@ -16,6 +16,7 @@ import {
   createLambda,
   debug,
   walkParentDirs,
+  cloneEnv,
 } from '@vercel/build-utils';
 import { installBundler } from './install-ruby';
 
@@ -63,12 +64,11 @@ async function bundleInstall(
     ['install', '--deployment', '--gemfile', gemfilePath, '--path', bundleDir],
     {
       stdio: 'pipe',
-      env: {
-        ...process.env,
+      env: cloneEnv(process.env, {
         BUNDLE_SILENCE_ROOT_WARNING: '1',
         BUNDLE_APP_CONFIG: bundleAppConfig,
         BUNDLE_JOBS: '4',
-      },
+      }),
     }
   );
 }

packages/static-build/src/index.ts

@@ -31,6 +31,7 @@ import {
   debug,
   NowBuildError,
   scanParentDirs,
+  cloneEnv,
 } from '@vercel/build-utils';
 import type { Route, RouteWithSrc } from '@vercel/routing-utils';
 import * as BuildOutputV1 from './utils/build-output-v1';
@@ -465,8 +466,7 @@ export const build: BuildV2 = async ({
           debug('Detected Gemfile');
           printInstall();
           const opts = {
-            env: {
-              ...process.env,
+            env: cloneEnv(process.env, {
               // See more: https://github.com/rubygems/rubygems/blob/a82d04856deba58be6b90f681a5e42a7c0f2baa7/bundler/lib/bundler/man/bundle-config.1.ronn
               BUNDLE_BIN: 'vendor/bin',
               BUNDLE_CACHE_PATH: 'vendor/cache',
@@ -476,7 +476,7 @@ export const build: BuildV2 = async ({
               BUNDLE_SILENCE_ROOT_WARNING: '1',
               BUNDLE_DISABLE_SHARED_GEMS: '1',
               BUNDLE_DISABLE_VERSION_CHECK: '1',
-            },
+            }),
           };
           await runBundleInstall(workPath, [], opts, meta);
           isBundleInstall = true;