[heft-lint-plugin] Lint files selected by ESLint flat config

apps/playwright-browser-tunnel/eslint.config.js

@@ -3,6 +3,9 @@
 
 const nodeTrustedToolProfile = require('local-node-rig/profiles/default/includes/eslint/flat/profile/node-trusted-tool');
 const friendlyLocalsMixin = require('local-node-rig/profiles/default/includes/eslint/flat/mixins/friendly-locals');
+const {
+  withoutTypeInformation
+} = require('local-node-rig/profiles/default/includes/eslint/flat/without-type-information');
 
 module.exports = [
   ...nodeTrustedToolProfile,
@@ -14,5 +17,8 @@ module.exports = [
         tsconfigRootDir: __dirname
       }
     }
-  }
+  },
+  // The Playwright config and test files are not part of the project's TypeScript program (they are excluded
+  // from tsconfig.json), so lint them with only the non-type-aware rules.
+  ...withoutTypeInformation({ files: ['playwright.config.ts', 'tests/**/*.ts'] })
 ];

apps/playwright-browser-tunnel/playwright.config.ts

@@ -1,3 +1,6 @@
+// Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.
+// See LICENSE in the project root for license information.
+
 import { defineConfig, devices } from '@playwright/test';
 
 export default defineConfig({

apps/playwright-browser-tunnel/tests/testFixture.ts

@@ -2,14 +2,18 @@
 // See LICENSE in the project root for license information.
 
 import { test as base } from '@playwright/test';
-import { tunneledBrowser } from '../src/tunneledBrowserConnection';
 
-export const test = base.extend({
+import {
+  createTunneledBrowserAsync,
+  type IDisposableTunneledBrowser
+} from '../src/tunneledBrowserConnection';
+
+export const test: typeof base = base.extend({
   browser: [
     async ({ browserName, launchOptions, channel, headless }, use) => {
-      console.log(`Starting tunnel server for browser: ${browserName}, channel: ${channel}`);
+      console.info(`Starting tunnel server for browser: ${browserName}, channel: ${channel}`);
 
-      await using tunnel = await tunneledBrowser(browserName, {
+      await using tunnel: IDisposableTunneledBrowser = await createTunneledBrowserAsync(browserName, {
         channel,
         headless,
         ...launchOptions

build-tests/eslint-9-test/.eslint-bulk-suppressions.json

@@ -4,6 +4,11 @@
       "file": "src/index.ts",
       "scopeId": ".",
       "rule": "@typescript-eslint/naming-convention"
+    },
+    {
+      "file": "src/non-program.custom",
+      "scopeId": ".",
+      "rule": "no-undef"
     }
   ]
 }

build-tests/eslint-9-test/eslint.config.js

@@ -7,6 +7,9 @@ const nodeTrustedToolProfile = require('local-node-rig/profiles/default/includes
 const friendlyLocalsMixin = require('local-node-rig/profiles/default/includes/eslint/flat/mixins/friendly-locals');
 
 module.exports = [
+  {
+    ignores: ['coverage/**']
+  },
   ...nodeTrustedToolProfile,
   ...friendlyLocalsMixin,
   {
@@ -25,5 +28,11 @@ module.exports = [
         tsconfigRootDir: __dirname
       }
     }
+  },
+  {
+    files: ['**/*.custom'],
+    rules: {
+      'no-undef': 'warn'
+    }
   }
 ];

build-tests/eslint-9-test/src/__snapshots__/sarif.test.ts.snap

@@ -16,6 +16,16 @@ Object {
             "uri": "src/sarif.test.ts",
           },
         },
+        Object {
+          "location": Object {
+            "uri": "eslint.config.js",
+          },
+        },
+        Object {
+          "location": Object {
+            "uri": "src/non-program.custom",
+          },
+        },
       ],
       "results": Array [
         Object {
@@ -78,6 +88,36 @@ Object {
             },
           ],
         },
+        Object {
+          "level": "warning",
+          "locations": Array [
+            Object {
+              "physicalLocation": Object {
+                "artifactLocation": Object {
+                  "index": 3,
+                  "uri": "src/non-program.custom",
+                },
+                "region": Object {
+                  "endColumn": 14,
+                  "endLine": 1,
+                  "startColumn": 1,
+                  "startLine": 1,
+                },
+              },
+            },
+          ],
+          "message": Object {
+            "text": "'missingGlobal' is not defined.",
+          },
+          "ruleId": "no-undef",
+          "ruleIndex": 2,
+          "suppressions": Array [
+            Object {
+              "justification": "",
+              "kind": "external",
+            },
+          ],
+        },
       ],
       "tool": Object {
         "driver": Object {
@@ -100,6 +140,14 @@ Object {
                 "text": "Enforce naming conventions for everything across a codebase",
               },
             },
+            Object {
+              "helpUri": "https://eslint.org/docs/latest/rules/no-undef",
+              "id": "no-undef",
+              "properties": Object {},
+              "shortDescription": Object {
+                "text": "Disallow the use of undeclared variables unless mentioned in \`/*global */\` comments",
+              },
+            },
           ],
           "version": "9.37.0",
         },

build-tests/eslint-9-test/src/non-program.custom

@@ -0,0 +1 @@
+missingGlobal;

build-tests/rush-redis-cobuild-plugin-integration-test/eslint.config.js

@@ -5,6 +5,11 @@ const nodeProfile = require('local-node-rig/profiles/default/includes/eslint/fla
 
 module.exports = [
   ...nodeProfile,
+  // The sandbox contains checked-in fixture repositories (including bootstrap scripts) that are not source
+  // code for this project and should not be linted.
+  {
+    ignores: ['sandbox/**']
+  },
   {
     files: ['**/*.ts', '**/*.tsx'],
     languageOptions: {

common/changes/@rushstack/eslint-config/eslint-config-ignore-build-output_2026-09-20-04-00-00.json

@@ -0,0 +1,9 @@
+{
+  "changes": [
+    {
+      "packageName": "@rushstack/eslint-config",
+      "comment": "Globally ignore build-output folders (`lib`, `lib-*`, `dist`, `temp`, `coverage`) so that generated output is not linted, which matters for tools that enumerate files from the ESLint configuration (ESLint's flat config does not respect `.gitignore`).",
+      "type": "minor"
+    }
+  ]
+}

common/changes/@rushstack/heft-lint-plugin/eslint-flat-config-files_2026-09-01-12-00-00.json

@@ -0,0 +1,9 @@
+{
+  "changes": [
+    {
+      "packageName": "@rushstack/heft-lint-plugin",
+      "comment": "Lint files selected by ESLint flat config even when they are not part of the TypeScript program.",
+      "type": "minor"
+    }
+  ]
+}

common/changes/@rushstack/package-extractor/heft-lint-flat-config-ignore-test-output_2026-09-20-04-00-00.json

@@ -0,0 +1,9 @@
+{
+  "changes": [
+    {
+      "packageName": "@rushstack/package-extractor",
+      "comment": "",
+      "type": "none"
+    }
+  ]
+}

common/changes/@rushstack/playwright-browser-tunnel/heft-lint-flat-config-files_2026-09-16-04-00-00.json

@@ -0,0 +1,9 @@
+{
+  "changes": [
+    {
+      "packageName": "@rushstack/playwright-browser-tunnel",
+      "comment": "",
+      "type": "none"
+    }
+  ]
+}

eslint/eslint-config/src/flat/profile/_common.ts

@@ -242,6 +242,13 @@ const commonConfig: Linter.Config[] = [
   // so we simply ignore them.
   globalIgnores(['**/*.d.ts']) as Linter.Config,
 
+  // Build output and other generated folders are not source code and should never be linted.  This is
+  // particularly important for tools that enumerate files from the ESLint configuration itself (rather than
+  // only linting a known set of source files), since ESLint's flat config does not respect ".gitignore".
+  // These patterns are anchored to the project root (they are evaluated relative to the cwd), so a source
+  // folder such as "src/lib" is not affected.
+  globalIgnores(['lib/**', 'lib-*/**', 'dist/**', 'temp/**', 'coverage/**']) as Linter.Config,
+
   {
     files: ['**/*.ts', '**/*.tsx'],
     languageOptions: {

eslint/local-eslint-config/.gitignore

@@ -1,3 +1,4 @@
 /flat/mixins
 /flat/patch
-/flat/profile
+/flat/profile
+/flat/without-type-information.js