feat: Enable eslint.config.js lookup from CLI

.eslintrc.js

@@ -1,3 +1,20 @@
+/*
+ * IMPORTANT!
+ *
+ * Any changes made to this file must also be made to eslint.config.js.
+ *
+ * Internally, ESLint is using the eslint.config.js file to lint itself.
+ * This file is needed too, because:
+ *
+ * 1. There are tests that expect .eslintrc.js to be present to actually run.
+ * 2. ESLint VS Code extension expects eslintrc config files to be
+ *    present to work correctly.
+ *
+ * Once we no longer need to support both eslintrc and flat config, we will
+ * remove this file.
+ */
+
+
 "use strict";
 
 const path = require("path");

bin/eslint.js

@@ -9,9 +9,6 @@
 
 "use strict";
 
-// to use V8's code cache to speed up instantiation time
-require("v8-compile-cache");
-
 // must do this initialization *before* other requires in order to work
 if (process.argv.includes("--debug")) {
     require("debug").enable("eslint:*,-eslint:code-path,eslintrc:*");
@@ -137,6 +134,7 @@ ${message}`);
     // Otherwise, call the CLI.
     process.exitCode = await require("../lib/cli").execute(
         process.argv,
-        process.argv.includes("--stdin") ? await readStdin() : null
+        process.argv.includes("--stdin") ? await readStdin() : null,
+        true
     );
 }()).catch(onFatalError);

docs/src/user-guide/configuring/configuration-files-new.md

@@ -10,7 +10,7 @@ eleventyNavigation:
 ---
 
 ::: warning
-This is an experimental feature that is not enabled by default. You can use the configuration system described on this page by using the `FlatESLint` class, the `FlatRuleTester` class, or by setting `configType: "flat"` in the `Linter` class.
+This is an experimental feature. To opt-in, place a `eslint.config.js` file in the root of your project. If you are using the API, you can use the configuration system described on this page by using the `FlatESLint` class, the `FlatRuleTester` class, or by setting `configType: "flat"` in the `Linter` class.
 :::
 
 ## Configuration File

eslint.config.js

@@ -5,12 +5,29 @@
 
 "use strict";
 
+/*
+ * IMPORTANT!
+ *
+ * Any changes made to this file must also be made to .eslintrc.js.
+ *
+ * Internally, ESLint is using the eslint.config.js file to lint itself.
+ * The .eslintrc.js file is needed too, because:
+ *
+ * 1. There are tests that expect .eslintrc.js to be present to actually run.
+ * 2. ESLint VS Code extension expects eslintrc config files to be
+ *    present to work correctly.
+ *
+ * Once we no longer need to support both eslintrc and flat config, we will
+ * remove .eslintrc.js.
+ */
+
 //-----------------------------------------------------------------------------
 // Requirements
 //-----------------------------------------------------------------------------
 
 const path = require("path");
 const internalPlugin = require("eslint-plugin-internal-rules");
+const eslintPlugin = require("eslint-plugin-eslint-plugin");
 const { FlatCompat } = require("@eslint/eslintrc");
 const globals = require("globals");
 
@@ -24,7 +41,6 @@ const compat = new FlatCompat({
 
 const INTERNAL_FILES = {
     CLI_ENGINE_PATTERN: "lib/cli-engine/**/*",
-    INIT_PATTERN: "lib/init/**/*",
     LINTER_PATTERN: "lib/linter/**/*",
     RULE_TESTER_PATTERN: "lib/rule-tester/**/*",
     RULES_PATTERN: "lib/rules/**/*",
@@ -60,11 +76,6 @@ function createInternalFilesPatterns(pattern = null) {
         }));
 }
 
-
-//-----------------------------------------------------------------------------
-// Config
-//-----------------------------------------------------------------------------
-
 module.exports = [
     ...compat.extends("eslint", "plugin:eslint-plugin/recommended"),
     {
@@ -101,13 +112,25 @@ module.exports = [
             "eslint-plugin/test-case-shorthand-strings": "error",
             "internal-rules/multiline-comment-style": "error"
         }
-
+    },
+    {
+        files: ["tools/*.js"],
+        rules: {
+            "no-console": "off"
+        }
     },
     {
         files: ["lib/rules/*", "tools/internal-rules/*"],
-        ignores: ["index.js"],
+        ignores: ["**/index.js"],
         rules: {
-            "eslint-plugin/prefer-object-rule": "error",
+            ...eslintPlugin.configs["rules-recommended"].rules,
+            "eslint-plugin/no-missing-message-ids": "error",
+            "eslint-plugin/no-unused-message-ids": "error",
+            "eslint-plugin/prefer-message-ids": "error",
+            "eslint-plugin/prefer-placeholders": "error",
+            "eslint-plugin/prefer-replace-text": "error",
+            "eslint-plugin/report-message-format": ["error", "[^a-z].*\\.$"],
+            "eslint-plugin/require-meta-docs-description": ["error", { pattern: "^(Enforce|Require|Disallow)" }],
             "internal-rules/no-invalid-meta": "error"
         }
     },
@@ -119,7 +142,16 @@ module.exports = [
         }
     },
     {
-        files: ["tests/**/*"],
+        files: ["tests/lib/rules/*", "tests/tools/internal-rules/*"],
+        rules: {
+            ...eslintPlugin.configs["tests-recommended"].rules,
+            "eslint-plugin/prefer-output-null": "error",
+            "eslint-plugin/test-case-property-ordering": "error",
+            "eslint-plugin/test-case-shorthand-strings": "error"
+        }
+    },
+    {
+        files: ["tests/**/*.js"],
         languageOptions: {
             globals: {
                 ...globals.mocha
@@ -147,17 +179,7 @@ module.exports = [
         files: [INTERNAL_FILES.CLI_ENGINE_PATTERN],
         rules: {
             "n/no-restricted-require": ["error", [
-                ...createInternalFilesPatterns(INTERNAL_FILES.CLI_ENGINE_PATTERN),
-                resolveAbsolutePath("lib/init/index.js")
-            ]]
-        }
-    },
-    {
-        files: [INTERNAL_FILES.INIT_PATTERN],
-        rules: {
-            "n/no-restricted-require": ["error", [
-                ...createInternalFilesPatterns(INTERNAL_FILES.INIT_PATTERN),
-                resolveAbsolutePath("lib/rule-tester/index.js")
+                ...createInternalFilesPatterns(INTERNAL_FILES.CLI_ENGINE_PATTERN)
             ]]
         }
     },
@@ -168,7 +190,6 @@ module.exports = [
                 ...createInternalFilesPatterns(INTERNAL_FILES.LINTER_PATTERN),
                 "fs",
                 resolveAbsolutePath("lib/cli-engine/index.js"),
-                resolveAbsolutePath("lib/init/index.js"),
                 resolveAbsolutePath("lib/rule-tester/index.js")
             ]]
         }
@@ -180,7 +201,6 @@ module.exports = [
                 ...createInternalFilesPatterns(INTERNAL_FILES.RULES_PATTERN),
                 "fs",
                 resolveAbsolutePath("lib/cli-engine/index.js"),
-                resolveAbsolutePath("lib/init/index.js"),
                 resolveAbsolutePath("lib/linter/index.js"),
                 resolveAbsolutePath("lib/rule-tester/index.js"),
                 resolveAbsolutePath("lib/source-code/index.js")
@@ -193,7 +213,6 @@ module.exports = [
             "n/no-restricted-require": ["error", [
                 ...createInternalFilesPatterns(),
                 resolveAbsolutePath("lib/cli-engine/index.js"),
-                resolveAbsolutePath("lib/init/index.js"),
                 resolveAbsolutePath("lib/linter/index.js"),
                 resolveAbsolutePath("lib/rule-tester/index.js"),
                 resolveAbsolutePath("lib/source-code/index.js")
@@ -207,7 +226,6 @@ module.exports = [
                 ...createInternalFilesPatterns(INTERNAL_FILES.SOURCE_CODE_PATTERN),
                 "fs",
                 resolveAbsolutePath("lib/cli-engine/index.js"),
-                resolveAbsolutePath("lib/init/index.js"),
                 resolveAbsolutePath("lib/linter/index.js"),
                 resolveAbsolutePath("lib/rule-tester/index.js"),
                 resolveAbsolutePath("lib/rules/index.js")
@@ -219,8 +237,7 @@ module.exports = [
         rules: {
             "n/no-restricted-require": ["error", [
                 ...createInternalFilesPatterns(INTERNAL_FILES.RULE_TESTER_PATTERN),
-                resolveAbsolutePath("lib/cli-engine/index.js"),
-                resolveAbsolutePath("lib/init/index.js")
+                resolveAbsolutePath("lib/cli-engine/index.js")
             ]]
         }
     }