eslint · fasttime · Apr 2, 2025 · Jan 29, 2025 · Jan 30, 2025 · Mar 7, 2025
@@ -71,11 +71,19 @@ jobs:
             matrix:
                 os: [ubuntu-latest]
                 node: [23.x, 22.x, 21.x, 20.x, 18.x, "18.18.0"]
+                NODE_OPTIONS: [""]
                 include:
                     - os: windows-latest
                       node: "lts/*"
                     - os: macOS-latest
                       node: "lts/*"
+                    - os: ubuntu-latest
+                      node: 22.x
+
+                      # `--experimental-strip-types` is enabled by default in Node.js 23.x.
+                      # This additional environment is necessary only to test `--experimental-transform-types`,
+                      # as it is not enabled by default in any Node.js version yet.
+                      NODE_OPTIONS: "--experimental-transform-types"
         runs-on: ${{ matrix.os }}
         steps:
             - uses: actions/checkout@v4
@@ -85,6 +93,8 @@ jobs:
             - name: Install Packages
               run: npm install
             - name: Test
+              env:
+                  NODE_OPTIONS: ${{ matrix.NODE_OPTIONS }}
               run: node Makefile mocha
             - name: Fuzz Test
               run: node Makefile fuzz

@@ -673,6 +673,16 @@ You can then create a configuration file with a `.ts`, `.mts`, or `.cts` extensi
 ESLint does not perform type checking on your configuration file and does not apply any settings from `tsconfig.json`.
 :::
 
+### Native TypeScript Support
+
+If you're using **Node.js >= 22.6.0**, you can load TypeScript configuration files natively without requiring [`jiti`](https://github.com/unjs/jiti). This is possible thanks to the [**`--experimental-strip-types`**](https://nodejs.org/docs/latest-v22.x/api/cli.html#--experimental-strip-types) flag.
+
+Since this feature is still experimental, you must also enable the `unstable_native_nodejs_ts_config` flag.
+
+```bash
+npx --node-options='--experimental-strip-types' eslint --flag unstable_native_nodejs_ts_config
+```
+
 ### Configuration File Precedence
 
 If you have multiple ESLint configuration files, ESLint prioritizes JavaScript files over TypeScript files. The order of precedence is as follows:

@@ -21,16 +21,19 @@ const { FlatConfigArray } = require("./flat-config-array");
 //-----------------------------------------------------------------------------
 
 /**
- * @typedef {import("../shared/types").FlatConfigObject} FlatConfigObject
- * @typedef {import("../shared/types").FlatConfigArray} FlatConfigArray
+ * @import { ConfigData, ConfigData as FlatConfigObject } from "../shared/types.js";
+ */
+
+/**
  * @typedef {Object} ConfigLoaderOptions
  * @property {string|false|undefined} configFile The path to the config file to use.
  * @property {string} cwd The current working directory.
  * @property {boolean} ignoreEnabled Indicates if ignore patterns should be honored.
  * @property {FlatConfigArray} [baseConfig] The base config to use.
  * @property {Array<FlatConfigObject>} [defaultConfigs] The default configs to use.
  * @property {Array<string>} [ignorePatterns] The ignore patterns to use.
- * @property {FlatConfigObject|Array<FlatConfigObject>} overrideConfig The override config to use.
+ * @property {FlatConfigObject|Array<FlatConfigObject>} [overrideConfig] The override config to use.
+ * @property {boolean} [hasUnstableNativeNodeJsTSConfigFlag] The flag to indicate whether the `unstable_native_nodejs_ts_config` flag is enabled.
  */
 
 //------------------------------------------------------------------------------
@@ -108,12 +111,87 @@ function isRunningInDeno() {
 	return !!globalThis.Deno;
 }
 
+/**
+ * Checks if native TypeScript support is
+ * enabled in the current Node.js process.
+ *
+ * This function determines if the
+ * {@linkcode NodeJS.ProcessFeatures.typescript | typescript}
+ * feature is present in the
+ * {@linkcode process.features} object
+ * and if its value is either "strip" or "transform".
+ * @returns {boolean} `true` if native TypeScript support is enabled, otherwise `false`.
+ * @since 9.24.0
+ */
+function isNativeTypeScriptSupportEnabled() {
+	return (
+		// eslint-disable-next-line n/no-unsupported-features/node-builtins -- it's still an experimental feature.
+		["strip", "transform"].includes(process.features.typescript)
+	);
+}
+
+/**
+ * Load the TypeScript configuration file.
+ * @param {string} filePath The absolute file path to load.
+ * @param {URL} fileURL The file URL to load.
+ * @param {number} mtime The last modified timestamp of the file.
+ * @returns {Promise<any>} The configuration loaded from the file.
+ * @since 9.24.0
+ */
+async function loadTypeScriptConfigFileWithJiti(filePath, fileURL, mtime) {
+	// eslint-disable-next-line no-use-before-define -- `ConfigLoader.loadJiti` can be overwritten for testing
+	const { createJiti } = await ConfigLoader.loadJiti().catch(() => {
+		throw new Error(
+			"The 'jiti' library is required for loading TypeScript configuration files. Make sure to install it.",
+		);
+	});
+
+	// `createJiti` was added in jiti v2.
+	if (typeof createJiti !== "function") {
+		throw new Error(
+			"You are using an outdated version of the 'jiti' library. Please update to the latest version of 'jiti' to ensure compatibility and access to the latest features.",
+		);
+	}
+
+	/*
+	 * Disabling `moduleCache` allows us to reload a
+	 * config file when the last modified timestamp changes.
+	 */
+
+	const jiti = createJiti(__filename, {
+		moduleCache: false,
+		interopDefault: false,
+	});
+	const config = await jiti.import(fileURL.href);
+
+	importedConfigFileModificationTime.set(filePath, mtime);
+
+	return config?.default ?? config;
+}
+
+/**
+ * Dynamically imports a module from the given file path.
+ * @param {string} filePath The absolute file path of the module to import.
+ * @param {URL} fileURL The file URL to load.
+ * @param {number} mtime The last modified timestamp of the file.
+ * @returns {Promise<any>} - A {@linkcode Promise | promise} that resolves to the imported ESLint config.
+ * @since 9.24.0
+ */
+async function dynamicImportConfig(filePath, fileURL, mtime) {
+	const module = await import(fileURL.href);
+
+	importedConfigFileModificationTime.set(filePath, mtime);
+
+	return module.default;
+}
+
 /**
  * Load the config array from the given filename.
  * @param {string} filePath The filename to load from.
+ * @param {boolean} hasUnstableNativeNodeJsTSConfigFlag The flag to indicate whether the `unstable_native_nodejs_ts_config` flag is enabled.
  * @returns {Promise<any>} The config loaded from the config file.
  */
-async function loadConfigFile(filePath) {
+async function loadConfigFile(filePath, hasUnstableNativeNodeJsTSConfigFlag) {
 	debug(`Loading config from ${filePath}`);
 
 	const fileURL = pathToFileURL(filePath);
@@ -161,44 +239,36 @@ async function loadConfigFile(filePath) {
 	 *
 	 * When Node.js supports native TypeScript imports, we can remove this check.
 	 */
-	if (isTS && !isDeno && !isBun) {
-		// eslint-disable-next-line no-use-before-define -- `ConfigLoader.loadJiti` can be overwritten for testing
-		const { createJiti } = await ConfigLoader.loadJiti().catch(() => {
-			throw new Error(
-				"The 'jiti' library is required for loading TypeScript configuration files. Make sure to install it.",
-			);
-		});
 
-		// `createJiti` was added in jiti v2.
-		if (typeof createJiti !== "function") {
+	if (isTS) {
+		if (hasUnstableNativeNodeJsTSConfigFlag) {
+			if (isNativeTypeScriptSupportEnabled()) {
+				return await dynamicImportConfig(filePath, fileURL, mtime);
+			}
+
+			if (!("typescript" in process.features)) {
+				throw new Error(
+					"The unstable_native_nodejs_ts_config flag is not supported in older versions of Node.js.",
+				);
+			}
+
 			throw new Error(
-				"You are using an outdated version of the 'jiti' library. Please update to the latest version of 'jiti' to ensure compatibility and access to the latest features.",
+				"The unstable_native_nodejs_ts_config flag is enabled, but native TypeScript support is not enabled in the current Node.js process. You need to either enable native TypeScript support by passing --experimental-strip-types or remove the unstable_native_nodejs_ts_config flag.",
 			);
 		}
 
-		/*
-		 * Disabling `moduleCache` allows us to reload a
-		 * config file when the last modified timestamp changes.
-		 */
-
-		const jiti = createJiti(__filename, {
-			moduleCache: false,
-			interopDefault: false,
-		});
-		const config = await jiti.import(fileURL.href);
-
-		importedConfigFileModificationTime.set(filePath, mtime);
-
-		return config?.default ?? config;
+		if (!isDeno && !isBun) {
+			return await loadTypeScriptConfigFileWithJiti(
+				filePath,
+				fileURL,
+				mtime,
+			);
+		}
 	}
 
 	// fallback to normal runtime behavior
 
-	const config = (await import(fileURL)).default;
-
-	importedConfigFileModificationTime.set(filePath, mtime);
-
-	return config;
+	return await dynamicImportConfig(filePath, fileURL, mtime);
 }
 
 //-----------------------------------------------------------------------------
@@ -495,6 +565,7 @@ class ConfigLoader {
 			ignoreEnabled,
 			ignorePatterns,
 			overrideConfig,
+			hasUnstableNativeNodeJsTSConfigFlag = false,
 			defaultConfigs = [],
 		} = options;
 
@@ -510,7 +581,10 @@ class ConfigLoader {
 		// load config file
 		if (configFilePath) {
 			debug(`Loading config file ${configFilePath}`);
-			const fileConfig = await loadConfigFile(configFilePath);
+			const fileConfig = await loadConfigFile(
+				configFilePath,
+				hasUnstableNativeNodeJsTSConfigFlag,
+			);
 
 			/*
 			 * It's possible that a config file could be empty or else

@@ -9,7 +9,10 @@
 // Typedefs
 //------------------------------------------------------------------------------
 
-/** @typedef {import("../types").Rule.RuleModule} Rule */
+/**
+ * @import { RuleDefinition } from "@eslint/core";
+ * @import { Linter } from "eslint";
+ */
 
 //------------------------------------------------------------------------------
 // Private Members
@@ -59,8 +62,8 @@ function parseRuleId(ruleId) {
 /**
  * Retrieves a rule instance from a given config based on the ruleId.
  * @param {string} ruleId The rule ID to look for.
- * @param {FlatConfig} config The config to search.
- * @returns {import("../shared/types").Rule|undefined} The rule if found
+ * @param {Linter.Config} config The config to search.
+ * @returns {RuleDefinition|undefined} The rule if found
  *      or undefined if not.
  */
 function getRuleFromConfig(ruleId, config) {
@@ -71,7 +74,7 @@ function getRuleFromConfig(ruleId, config) {
 
 /**
  * Gets a complete options schema for a rule.
- * @param {Rule} rule A rule object
+ * @param {RuleDefinition} rule A rule object
  * @throws {TypeError} If `meta.schema` is specified but is not an array, object or `false`.
  * @returns {Object|null} JSON Schema for the rule's options. `null` if `meta.schema` is `false`.
  */

@@ -28,6 +28,12 @@ const MINIMATCH_OPTIONS = { dot: true };
 // Types
 //-----------------------------------------------------------------------------
 
+/**
+ * @import { ESLintOptions } from "./eslint.js";
+ * @import { LintMessage, LintResult } from "../shared/types.js";
+ * @import { ConfigLoader, LegacyConfigLoader } from "../config/config-loader.js";
+ */
+
 /**
  * @typedef {Object} GlobSearch
  * @property {Array<string>} patterns The normalized patterns to use for a search.
@@ -115,7 +121,7 @@ function isNonEmptyString(value) {
  */
 function isArrayOfNonEmptyString(value) {
 	return (
-		Array.isArray(value) && value.length && value.every(isNonEmptyString)
+		Array.isArray(value) && !!value.length && value.every(isNonEmptyString)
 	);
 }
 
@@ -351,7 +357,7 @@ async function globSearch({
  *      as the user inputted them. Used for errors.
  * @param {Array<string>} options.unmatchedPatterns A non-empty array of absolute path glob patterns
  *      that were unmatched in the original search.
- * @returns {void} Always throws an error.
+ * @returns {Promise<never>} Always throws an error.
  * @throws {NoFilesFoundError} If the first unmatched pattern
  *      doesn't match any files even when there are no ignores.
  * @throws {AllFilesIgnoredError} If the first unmatched pattern
@@ -454,7 +460,7 @@ async function globMultiSearch({
 		}
 	}
 
-	// second loop for `fulfulled` results
+	// second loop for `fulfilled` results
 	return results.flatMap(result => result.value);
 }
 

@@ -52,19 +52,15 @@ const { ConfigLoader, LegacyConfigLoader } = require("../config/config-loader");
 //------------------------------------------------------------------------------
 
 // For VSCode IntelliSense
-/** @typedef {import("../cli-engine/cli-engine").ConfigArray} ConfigArray */
-/** @typedef {import("../shared/types").ConfigData} ConfigData */
-/** @typedef {import("../shared/types").DeprecatedRuleInfo} DeprecatedRuleInfo */
-/** @typedef {import("../shared/types").LintMessage} LintMessage */
-/** @typedef {import("../shared/types").LintResult} LintResult */
-/** @typedef {import("../shared/types").ParserOptions} ParserOptions */
-/** @typedef {import("../shared/types").Plugin} Plugin */
-/** @typedef {import("../shared/types").ResultsMeta} ResultsMeta */
-/** @typedef {import("../shared/types").RuleConf} RuleConf */
-/** @typedef {import("../types").Rule.RuleModule} Rule */
+/**
+ * @import { ConfigArray } from "../cli-engine/cli-engine.js";
+ * @import { CLIEngineLintReport } from "./legacy-eslint.js";
+ * @import { FlatConfigArray } from "../config/flat-config-array.js";
+ * @import { RuleDefinition } from "@eslint/core";
+ * @import { ConfigData, DeprecatedRuleInfo, LintMessage, LintResult, Plugin, ResultsMeta } from "../shared/types.js";
+ */
+
 /** @typedef {ReturnType<ConfigArray.extractConfig>} ExtractedConfig */
-/** @typedef {import('../cli-engine/cli-engine').CLIEngine} CLIEngine */
-/** @typedef {import('./legacy-eslint').CLIEngineLintReport} CLIEngineLintReport */
 
 /**
  * The options with which to configure the ESLint instance.
@@ -113,7 +109,7 @@ const removedFormatters = new Set([
 
 /**
  * Create rulesMeta object.
- * @param {Map<string,Rule>} rules a map of rules from which to generate the object.
+ * @param {Map<string,RuleDefinition>} rules a map of rules from which to generate the object.
  * @returns {Object} metadata for all enabled rules.
  */
 function createRulesMeta(rules) {
@@ -138,7 +134,7 @@ const usedDeprecatedRulesCache = new WeakMap();
 
 /**
  * Create used deprecated rule list.
- * @param {CLIEngine} eslint The CLIEngine instance.
+ * @param {ESLint} eslint The ESLint instance.
  * @param {string} maybeFilePath The absolute path to a lint target file or `"<text>"`.
  * @returns {DeprecatedRuleInfo[]} The used deprecated rule list.
  */
@@ -191,7 +187,7 @@ function getOrFindUsedDeprecatedRules(eslint, maybeFilePath) {
 /**
  * Processes the linting results generated by a CLIEngine linting report to
  * match the ESLint class's API.
- * @param {CLIEngine} eslint The CLIEngine instance.
+ * @param {ESLint} eslint The ESLint instance.
  * @param {CLIEngineLintReport} report The CLIEngine linting report to process.
  * @returns {LintResult[]} The processed linting results.
  */
@@ -347,7 +343,7 @@ function verifyText({
 /**
  * Checks whether a message's rule type should be fixed.
  * @param {LintMessage} message The message to check.
- * @param {FlatConfig} config The config for the file that generated the message.
+ * @param {FlatConfigArray} config The config for the file that generated the message.
  * @param {string[]} fixTypes An array of fix types to check.
  * @returns {boolean} Whether the message should be fixed.
  */
@@ -375,7 +371,7 @@ function createExtraneousResultsError() {
  * Creates a fixer function based on the provided fix, fixTypesSet, and config.
  * @param {Function|boolean} fix The original fix option.
  * @param {Set<string>} fixTypesSet A set of fix types to filter messages for fixing.
- * @param {FlatConfig} config The config for the file that generated the message.
+ * @param {FlatConfigArray} config The config for the file that generated the message.
  * @returns {Function|boolean} The fixer function or the original fix value.
  */
 function getFixerForFixTypes(fix, fixTypesSet, config) {
@@ -440,6 +436,9 @@ class ESLint {
 			ignoreEnabled: processedOptions.ignore,
 			ignorePatterns: processedOptions.ignorePatterns,
 			defaultConfigs,
+			hasUnstableNativeNodeJsTSConfigFlag: linter.hasFlag(
+				"unstable_native_nodejs_ts_config",
+			),
 		};
 
 		this.#configLoader = linter.hasFlag("unstable_config_lookup_from_file")