### Website Team
@@ -320,11 +325,11 @@ The following companies, organizations, and individuals support ESLint's ongoing
to get your logo on our READMEs and [website](https://eslint.org/sponsors).
Diamond Sponsors
-
Platinum Sponsors
+
Platinum Sponsors
Gold Sponsors
Silver Sponsors
Bronze Sponsors
-
+
Technology Sponsors
Technology sponsors allow us to use their products and services for free as part of a contribution to the open source ecosystem and our work.
diff --git a/bin/eslint.js b/bin/eslint.js
index 7f979557ee82..9b202a982331 100755
--- a/bin/eslint.js
+++ b/bin/eslint.js
@@ -157,19 +157,15 @@ ${getErrorMessage(error)}`;
// start the MCP server if `--mcp` is present
if (process.argv.includes("--mcp")) {
- const { mcpServer } = require("../lib/mcp/mcp-server");
- const {
- StdioServerTransport,
- } = require("@modelcontextprotocol/sdk/server/stdio.js");
-
- await mcpServer.connect(new StdioServerTransport());
+ console.warn(
+ "You can also run this command directly using 'npx @eslint/mcp@latest'.",
+ );
- // Note: do not use console.log() because stdout is part of the server transport
- console.error(`ESLint MCP server is running. cwd: ${process.cwd()}`);
+ const spawn = require("cross-spawn");
- process.on("SIGINT", () => {
- mcpServer.close();
- process.exitCode = 0;
+ spawn.sync("npx", ["@eslint/mcp@latest"], {
+ encoding: "utf8",
+ stdio: "inherit",
});
return;
}
diff --git a/conf/rule-type-list.json b/conf/rule-type-list.json
index 03a757808f20..05ddd3cb02af 100644
--- a/conf/rule-type-list.json
+++ b/conf/rule-type-list.json
@@ -69,7 +69,8 @@
"removed": "space-in-brackets",
"replacedBy": [
{ "rule": { "name": "object-curly-spacing" } },
- { "rule": { "name": "array-bracket-spacing" } }
+ { "rule": { "name": "array-bracket-spacing" } },
+ { "rule": { "name": "computed-property-spacing" } }
]
},
{
diff --git a/docs/package.json b/docs/package.json
index 9fc63463d42b..ff8817574ab6 100644
--- a/docs/package.json
+++ b/docs/package.json
@@ -1,7 +1,7 @@
{
"name": "docs-eslint",
"private": true,
- "version": "9.26.0",
+ "version": "9.27.0",
"description": "",
"main": "index.js",
"keywords": [],
diff --git a/docs/src/_data/rule_versions.json b/docs/src/_data/rule_versions.json
index dbded69dfbae..c497cace7193 100644
--- a/docs/src/_data/rule_versions.json
+++ b/docs/src/_data/rule_versions.json
@@ -309,7 +309,8 @@
"no-empty-static-block": "8.27.0",
"no-new-native-nonconstructor": "8.27.0",
"no-object-constructor": "8.50.0",
- "no-useless-assignment": "9.0.0-alpha.1"
+ "no-useless-assignment": "9.0.0-alpha.1",
+ "no-unassigned-vars": "9.27.0"
},
"removed": {
"generator-star": "1.0.0-rc-1",
diff --git a/docs/src/_data/rules.json b/docs/src/_data/rules.json
index c3f68d59278c..bd66c84caa20 100644
--- a/docs/src/_data/rules.json
+++ b/docs/src/_data/rules.json
@@ -337,6 +337,14 @@
"frozen": false,
"hasSuggestions": false
},
+ {
+ "name": "no-unassigned-vars",
+ "description": "Disallow `let` or `var` variables that are read but never assigned",
+ "recommended": false,
+ "fixable": false,
+ "frozen": false,
+ "hasSuggestions": false
+ },
{
"name": "no-undef",
"description": "Disallow the use of undeclared variables unless mentioned in `/*global */` comments",
@@ -743,7 +751,7 @@
"name": "no-array-constructor",
"description": "Disallow `Array` constructors",
"recommended": false,
- "fixable": false,
+ "fixable": true,
"frozen": false,
"hasSuggestions": true
},
@@ -3437,6 +3445,11 @@
"rule": {
"name": "array-bracket-spacing"
}
+ },
+ {
+ "rule": {
+ "name": "computed-property-spacing"
+ }
}
]
},
diff --git a/docs/src/_data/rules_meta.json b/docs/src/_data/rules_meta.json
index 9abf524e8166..291e85c82370 100644
--- a/docs/src/_data/rules_meta.json
+++ b/docs/src/_data/rules_meta.json
@@ -1347,6 +1347,11 @@
},
"max-params": {
"type": "suggestion",
+ "dialects": [
+ "typescript",
+ "javascript"
+ ],
+ "language": "javascript",
"docs": {
"description": "Enforce a maximum number of parameters in function definitions",
"recommended": false,
@@ -1612,6 +1617,7 @@
"recommended": false,
"url": "https://eslint.org/docs/latest/rules/no-array-constructor"
},
+ "fixable": "code",
"hasSuggestions": true
},
"no-async-promise-executor": {
@@ -3260,6 +3266,19 @@
},
"fixable": "whitespace"
},
+ "no-unassigned-vars": {
+ "type": "problem",
+ "dialects": [
+ "typescript",
+ "javascript"
+ ],
+ "language": "javascript",
+ "docs": {
+ "description": "Disallow `let` or `var` variables that are read but never assigned",
+ "recommended": false,
+ "url": "https://eslint.org/docs/latest/rules/no-unassigned-vars"
+ }
+ },
"no-undef": {
"type": "problem",
"defaultOptions": [
@@ -3539,6 +3558,11 @@
},
"no-useless-escape": {
"type": "suggestion",
+ "defaultOptions": [
+ {
+ "allowRegexCharacters": []
+ }
+ ],
"docs": {
"description": "Disallow unnecessary escape characters",
"recommended": true,
diff --git a/docs/src/_data/versions.json b/docs/src/_data/versions.json
index 5c985905e075..df69aa53e92d 100644
--- a/docs/src/_data/versions.json
+++ b/docs/src/_data/versions.json
@@ -6,7 +6,7 @@
"path": "/docs/head/"
},
{
- "version": "9.26.0",
+ "version": "9.27.0",
"branch": "latest",
"path": "/docs/latest/"
},
diff --git a/docs/src/contribute/core-rules.md b/docs/src/contribute/core-rules.md
index a2dbd04b75da..e5dd8991c5a6 100644
--- a/docs/src/contribute/core-rules.md
+++ b/docs/src/contribute/core-rules.md
@@ -117,6 +117,7 @@ When a rule is frozen, it means:
- **Bug fixes**: We will still fix confirmed bugs.
- **New ECMAScript features**: We will ensure compatibility with new ECMAScript features, meaning the rule will not break on new syntax.
+- **TypeScript support**: We will ensure compatibility with TypeScript syntax, meaning the rule will not break on TypeScript syntax and violations are appropriate for TypeScript.
- **New options**: We will **not** add any new options unless an option is the only way to fix a bug or support a newly-added ECMAScript feature.
If you find that a frozen rule would work better for you with a change, we recommend copying the rule source code and modifying it to fit your needs.
diff --git a/docs/src/contribute/package-json-conventions.md b/docs/src/contribute/package-json-conventions.md
index f347f154d733..16327785b46a 100644
--- a/docs/src/contribute/package-json-conventions.md
+++ b/docs/src/contribute/package-json-conventions.md
@@ -18,7 +18,7 @@ Here is a summary of the proposal in ABNF.
```abnf
name = life-cycle / main target? option* ":watch"?
life-cycle = "prepare" / "preinstall" / "install" / "postinstall" / "prepublish" / "preprepare" / "prepare" / "postprepare" / "prepack" / "postpack" / "prepublishOnly"
-main = "build" / "lint" ":fix"? / "release" / "start" / "test" / "fetch"
+main = "build" / "lint" ":fix"? / "fmt" ":check"? / "release" / "start" / "test" / "fetch"
target = ":" word ("-" word)* / extension ("+" extension)*
option = ":" word ("-" word)*
word = ALPHA +
@@ -27,7 +27,7 @@ extension = ( ALPHA / DIGIT )+
## Order
-The script names MUST appear in the package.json file in alphabetical order. The other conventions outlined in this document ensure that alphabetical order will coincide with logical groupings.
+The script names MUST appear in the `package.json` file in alphabetical order. The other conventions outlined in this document ensure that alphabetical order will coincide with logical groupings.
## Main Script Names
@@ -47,7 +47,7 @@ If a package contains any `fetch:*` scripts, there MAY be a script named `fetch`
### Release
-Scripts that have public side effects (publishing the web site, committing to Git, etc.) MUST begin with `release`.
+Scripts that have public side effects (publishing the website, committing to Git, etc.) MUST begin with `release`.
### Lint
@@ -57,6 +57,12 @@ If a package contains any `lint:*` scripts, there SHOULD be a script named `lint
If fixing is available, a linter MUST NOT apply fixes UNLESS the script contains the `:fix` modifier (see below).
+### Fmt
+
+Scripts that format source code MUST have names that begin with `fmt`.
+
+If a package contains any `fmt:*` scripts, there SHOULD be a script named `fmt` that applies formatting fixes to all source files. There SHOULD also be a script named `fmt:check` that validates code formatting without modifying files and exits non-zero if any files are out of compliance.
+
### Start
A `start` script is used to start a server. As of this writing, no ESLint package has more than one `start` script, so there's no need `start` to have any modifiers.
@@ -79,6 +85,10 @@ One or more of the following modifiers MAY be appended to the standard script na
If it's possible for a linter to fix problems that it finds, add a copy of the script with `:fix` appended to the end that also fixes.
+### Check
+
+If a script validates code or artifacts without making any modifications, append `:check` to the script name. This modifier is typically used for formatters (e.g., `fmt:check`) to verify that files conform to the expected format and to exit with a non-zero status if any issues are found. Scripts with the `:check` modifier MUST NOT alter any files or outputs.
+
### Target
The name of the target of the action being run. In the case of a `build` script, it SHOULD identify the build artifact(s), e.g. "javascript" or "css" or "website". In the case of a `lint` or `test` script, it SHOULD identify the item(s) being linted or tested. In the case of a `start` script, it SHOULD identify which server is starting.
diff --git a/docs/src/integrate/nodejs-api.md b/docs/src/integrate/nodejs-api.md
index 0f7e5c14706b..f3e91febbd1b 100644
--- a/docs/src/integrate/nodejs-api.md
+++ b/docs/src/integrate/nodejs-api.md
@@ -140,9 +140,9 @@ The `ESLint` constructor takes an `options` object. If you omit the `options` ob
- `options.allowInlineConfig` (`boolean`)
Default is `true`. If `false` is present, ESLint suppresses directive comments in source code. If this option is `false`, it overrides the `noInlineConfig` setting in your configurations.
-- `options.baseConfig` (`ConfigData | ConfigData[] | null`)
+- `options.baseConfig` (`Config | Config[] | null`)
Default is `null`. [Configuration object], extended by all configurations used with this instance. You can use this option to define the default settings that will be used if your configuration files don't configure it.
-- `options.overrideConfig` (`ConfigData | ConfigData[] | null`)
+- `options.overrideConfig` (`Config | Config[] | null`)
Default is `null`. [Configuration object], added after any existing configuration and therefore applies after what's contained in your configuration file (if used).
- `options.overrideConfigFile` (`null | true | string`)
Default is `null`. By default, ESLint searches for a configuration file. When this option is set to `true`, ESLint does not search for a configuration file. When this option is set to a `string` value, ESLint does not search for a configuration file, and uses the provided value as the path to the configuration file.
diff --git a/docs/src/pages/flags.md b/docs/src/pages/flags.md
index 4d12207180af..0d873fac6bf5 100644
--- a/docs/src/pages/flags.md
+++ b/docs/src/pages/flags.md
@@ -82,6 +82,16 @@ On the command line, you can specify feature flags using the `--flag` option. Yo
args: ["--flag", "flag_one", "--flag", "flag_two", "file.js"]
}) }}
+### Enable Feature Flags with Environment Variables
+
+You can also set feature flags using the `ESLINT_FLAGS` environment variable. Multiple flags can be specified as a comma-separated list and are merged with any flags passed on the CLI or in the API. For example, here's how you can add feature flags to your `.bashrc` or `.bash_profile` files:
+
+```bash
+export ESLINT_FLAGS="flag_one,flag_two"
+```
+
+This approach is especially useful in CI/CD pipelines or when you want to enable the same flags across multiple ESLint commands.
+
### Enable Feature Flags with the API
When using the API, you can pass a `flags` array to both the `ESLint` and `Linter` classes:
@@ -98,6 +108,10 @@ const linter = new Linter({
});
```
+::: tip
+The `ESLint` class also reads the `ESLINT_FLAGS` environment variable to set flags.
+:::
+
### Enable Feature Flags in VS Code
To enable flags in the VS Code ESLint Extension for the editor, specify the flags you'd like in the `eslint.options` setting in your `settings.json` file:
diff --git a/docs/src/rules/init-declarations.md b/docs/src/rules/init-declarations.md
index a6d9f4e6e568..846dd7075a7e 100644
--- a/docs/src/rules/init-declarations.md
+++ b/docs/src/rules/init-declarations.md
@@ -1,6 +1,8 @@
---
title: init-declarations
rule_type: suggestion
+related_rules:
+- no-unassigned-vars
---
diff --git a/docs/src/rules/max-params.md b/docs/src/rules/max-params.md
index 92d7dde8dfe5..456729237eea 100644
--- a/docs/src/rules/max-params.md
+++ b/docs/src/rules/max-params.md
@@ -29,6 +29,7 @@ This rule enforces a maximum number of parameters allowed in function definition
This rule has a number or object option:
* `"max"` (default `3`) enforces a maximum number of parameters in function definitions
+* `"countVoidThis"` (default `false`) counts a `this` declaration when the type is `void` (TypeScript only)
**Deprecated:** The object property `maximum` is deprecated; please use the object property `max` instead.
@@ -69,3 +70,63 @@ let foo2 = (bar, baz, qux) => {
```
:::
+
+### countVoidThis (TypeScript only)
+
+This rule has a TypeScript-specific option `countVoidThis` that allows you to count a `this` declaration when the type is `void`.
+
+Examples of **correct** TypeScript code for this rule with the default `{ "countVoidThis": false }` option:
+
+:::correct
+
+```ts
+/*eslint max-params: ["error", { "max": 2, "countVoidThis": false }]*/
+
+function hasNoThis(this: void, first: string, second: string) {
+ // ...
+}
+```
+
+:::
+
+Examples of **incorrect** TypeScript code for this rule with the default `{ "countVoidThis": false }` option:
+
+:::incorrect
+
+```ts
+/*eslint max-params: ["error", { "max": 2, "countVoidThis": false }]*/
+
+function hasNoThis(this: void, first: string, second: string, third: string) {
+ // ...
+}
+```
+
+:::
+
+Examples of **correct** TypeScript code for this rule with the `{ "countVoidThis": true }` option:
+
+:::correct
+
+```ts
+/*eslint max-params: ["error", { "max": 2, "countVoidThis": true }]*/
+
+function hasNoThis(this: void, first: string) {
+ // ...
+}
+```
+
+:::
+
+Examples of **incorrect** TypeScript code for this rule with the `{ "countVoidThis": true }` option:
+
+:::incorrect
+
+```ts
+/*eslint max-params: ["error", { "max": 2, "countVoidThis": true }]*/
+
+function hasNoThis(this: void, first: string, second: string) {
+ // ...
+}
+```
+
+:::
diff --git a/docs/src/rules/no-unassigned-vars.md b/docs/src/rules/no-unassigned-vars.md
new file mode 100644
index 000000000000..a2ae0ba393b7
--- /dev/null
+++ b/docs/src/rules/no-unassigned-vars.md
@@ -0,0 +1,141 @@
+---
+title: no-unassigned-vars
+rule_type: problem
+related_rules:
+- init-declarations
+- no-unused-vars
+- prefer-const
+---
+
+
+This rule flags `let` or `var` declarations that are never assigned a value but are still read or used in the code. Since these variables will always be `undefined`, their usage is likely a programming mistake.
+
+For example, if you check the value of a `status` variable, but it was never given a value, it will always be `undefined`:
+
+```js
+let status;
+
+// ...forgot to assign a value to status...
+
+if (status === 'ready') {
+ console.log('Ready!');
+}
+```
+
+## Rule Details
+
+Examples of **incorrect** code for this rule:
+
+::: incorrect
+
+```js
+/*eslint no-unassigned-vars: "error"*/
+
+let status;
+if (status === 'ready') {
+ console.log('Ready!');
+}
+
+let user;
+greet(user);
+
+function test() {
+ let error;
+ return error || "Unknown error";
+}
+
+let options;
+const { debug } = options || {};
+
+let flag;
+while (!flag) {
+ // Do something...
+}
+
+let config;
+function init() {
+ return config?.enabled;
+}
+```
+
+:::
+
+In TypeScript:
+
+::: incorrect
+
+```ts
+/*eslint no-unassigned-vars: "error"*/
+
+let value: number | undefined;
+console.log(value);
+```
+
+:::
+
+Examples of **correct** code for this rule:
+
+::: correct
+
+```js
+/*eslint no-unassigned-vars: "error"*/
+
+let message = "hello";
+console.log(message);
+
+let user;
+user = getUser();
+console.log(user.name);
+
+let count;
+count = 1;
+count++;
+
+// Variable is unused (should be reported by `no-unused-vars` only)
+let temp;
+
+let error;
+if (somethingWentWrong) {
+ error = "Something went wrong";
+}
+console.log(error);
+
+let item;
+for (item of items) {
+ process(item);
+}
+
+let config;
+function setup() {
+ config = { debug: true };
+}
+setup();
+console.log(config);
+
+let one = undefined;
+if (one === two) {
+ // Noop
+}
+```
+
+:::
+
+In TypeScript:
+
+::: correct
+
+```ts
+/*eslint no-unassigned-vars: "error"*/
+
+declare let value: number | undefined;
+console.log(value);
+```
+
+:::
+
+## When Not To Use It
+
+You can disable this rule if your code intentionally uses variables that are declared and used, but are never assigned a value. This might be the case in:
+
+- Legacy codebases where uninitialized variables are used as placeholders.
+- Certain TypeScript use cases where variables are declared with a type and intentionally left unassigned (though using `declare` is preferred).
diff --git a/docs/src/rules/no-unused-vars.md b/docs/src/rules/no-unused-vars.md
index 96e70e6becc0..872a888bed50 100644
--- a/docs/src/rules/no-unused-vars.md
+++ b/docs/src/rules/no-unused-vars.md
@@ -2,6 +2,7 @@
title: no-unused-vars
rule_type: problem
related_rules:
+- no-unassigned-vars
- no-useless-assignment
---
diff --git a/docs/src/rules/no-useless-escape.md b/docs/src/rules/no-useless-escape.md
index ff173c229c2f..05375e3df4ad 100644
--- a/docs/src/rules/no-useless-escape.md
+++ b/docs/src/rules/no-useless-escape.md
@@ -67,6 +67,42 @@ Examples of **correct** code for this rule:
:::
+## Options
+
+This rule has an object option:
+
+* `allowRegexCharacters` - An array of characters that should be allowed to have unnecessary escapes in regular expressions. This is useful for characters like `-` where escaping can prevent accidental character ranges. For example, in `/[0\-]/`, the escape is technically unnecessary but helps prevent the pattern from becoming a range if another character is added later (e.g., `/[0\-9]/` vs `/[0-9]/`).
+
+### allowRegexCharacters
+
+Examples of **incorrect** code for the `{ "allowRegexCharacters": ["-"] }` option:
+
+::: incorrect
+
+```js
+/*eslint no-useless-escape: ["error", { "allowRegexCharacters": ["-"] }]*/
+
+/\!/;
+/\@/;
+/[a-z\^]/;
+```
+
+:::
+
+Examples of **correct** code for the `{ "allowRegexCharacters": ["-"] }` option:
+
+::: correct
+
+```js
+/*eslint no-useless-escape: ["error", { "allowRegexCharacters": ["-"] }]*/
+
+/[0\-]/;
+/[\-9]/;
+/a\-b/;
+```
+
+:::
+
## When Not To Use It
If you don't want to be notified about unnecessary escapes, you can safely disable this rule.
diff --git a/docs/src/rules/prefer-const.md b/docs/src/rules/prefer-const.md
index b61b5e6ae73d..449a41b82a6e 100644
--- a/docs/src/rules/prefer-const.md
+++ b/docs/src/rules/prefer-const.md
@@ -3,6 +3,7 @@ title: prefer-const
rule_type: suggestion
related_rules:
- no-var
+- no-unassigned-vars
- no-use-before-define
---
diff --git a/docs/src/use/configure/combine-configs.md b/docs/src/use/configure/combine-configs.md
index cf2c33ee956a..89aee283f460 100644
--- a/docs/src/use/configure/combine-configs.md
+++ b/docs/src/use/configure/combine-configs.md
@@ -11,7 +11,7 @@ In many cases, you won't write an ESLint config file from scratch, but rather, y
## Apply a Config Object
-If you are importing an object from another module, in most cases, you can just insert the object directly into your config file's exported array. For example, you can use the recommended rule configurations for JavaScript by importing the `recommended` config and using it in your array:
+If you are importing an object from another module, in most cases, you can just pass the object directly to the `defineConfig()` helper. For example, you can use the recommended rule configurations for JavaScript by importing the `recommended` config and using it in your array:
```js
// eslint.config.js
@@ -54,7 +54,7 @@ Here, the `js/recommended` config object is applied only to files that match the
## Apply a Config Array
-If you are importing an array from another module, insert the array directly into your exported array. Here's an example:
+If you are importing an array from another module, pass the array directly to the `defineConfig()` helper. Here's an example:
```js
// eslint.config.js
diff --git a/docs/src/use/configure/configuration-files.md b/docs/src/use/configure/configuration-files.md
index f3a789aadbe5..119a73dbc96c 100644
--- a/docs/src/use/configure/configuration-files.md
+++ b/docs/src/use/configure/configuration-files.md
@@ -90,14 +90,40 @@ Each configuration object contains all of the information ESLint needs to execut
Patterns specified in `files` and `ignores` use [`minimatch`](https://www.npmjs.com/package/minimatch) syntax and are evaluated relative to the location of the `eslint.config.js` file. If using an alternate config file via the `--config` command line option, then all patterns are evaluated relative to the current working directory.
:::
-You can use a combination of `files` and `ignores` to determine which files the configuration object should apply to and which not. By default, ESLint lints files that match the patterns `**/*.js`, `**/*.cjs`, and `**/*.mjs`. Those files are always matched unless you explicitly exclude them using [global ignores](#globally-ignoring-files-with-ignores).
-Because config objects that don't specify `files` or `ignores` apply to all files that have been matched by any other configuration object, they will apply to all JavaScript files. For example:
+You can use a combination of `files` and `ignores` to determine which files the configuration object should apply to and which not. Here's an example:
```js
// eslint.config.js
import { defineConfig } from "eslint/config";
export default defineConfig([
+ // matches all files ending with .js
+ {
+ files: ["**/*.js"],
+ rules: {
+ semi: "error",
+ },
+ },
+
+ // matches all files ending with .js except those in __tests
+ {
+ files: ["**/*.js"],
+ ignores: ["__tests/**"],
+ rules: {
+ "no-console": "error",
+ },
+ },
+]);
+```
+
+Configuration objects without `files` or `ignores` are automatically applied to any file that is matched by any other configuration object. For example:
+
+```js
+// eslint.config.js
+import { defineConfig } from "eslint/config";
+
+export default defineConfig([
+ // matches all files because it doesn't specify the `files` or `ignores` key
{
rules: {
semi: "error",
@@ -108,6 +134,10 @@ export default defineConfig([
With this configuration, the `semi` rule is enabled for all files that match the default files in ESLint. So if you pass `example.js` to ESLint, the `semi` rule is applied. If you pass a non-JavaScript file, like `example.txt`, the `semi` rule is not applied because there are no other configuration objects that match that filename. (ESLint outputs an error message letting you know that the file was ignored due to missing configuration.)
+::: important
+By default, ESLint lints files that match the patterns `**/*.js`, `**/*.cjs`, and `**/*.mjs`. Those files are always matched unless you explicitly exclude them using [global ignores](#globally-ignoring-files-with-ignores).
+:::
+
#### Excluding files with `ignores`
You can limit which files a configuration object applies to by specifying a combination of `files` and `ignores` patterns. For example, you may want certain rules to apply only to files in your `src` directory:
@@ -129,6 +159,7 @@ export default defineConfig([
Here, only the JavaScript files in the `src` directory have the `semi` rule applied. If you run ESLint on files in another directory, this configuration object is skipped. By adding `ignores`, you can also remove some of the files in `src` from this configuration object:
```js
+// eslint.config.js
import { defineConfig } from "eslint/config";
export default defineConfig([
@@ -145,6 +176,7 @@ export default defineConfig([
This configuration object matches all JavaScript files in the `src` directory except those that end with `.config.js`. You can also use negation patterns in `ignores` to exclude files from the ignore patterns, such as:
```js
+// eslint.config.js
import { defineConfig } from "eslint/config";
export default defineConfig([
@@ -165,6 +197,7 @@ Non-global `ignores` patterns can only match file names. A pattern like `"dir-to
If `ignores` is used without `files` and there are other keys (such as `rules`), then the configuration object applies to all linted files except the ones excluded by `ignores`, for example:
```js
+// eslint.config.js
import { defineConfig } from "eslint/config";
export default defineConfig([
diff --git a/docs/src/use/formatters/html-formatter-example.html b/docs/src/use/formatters/html-formatter-example.html
index e657bdc7ab1c..3b75a1d772b1 100644
--- a/docs/src/use/formatters/html-formatter-example.html
+++ b/docs/src/use/formatters/html-formatter-example.html
@@ -118,7 +118,7 @@
ESLint Report
- 8 problems (4 errors, 4 warnings) - Generated on Fri May 02 2025 21:32:27 GMT+0000 (Coordinated Universal Time)
+ 8 problems (4 errors, 4 warnings) - Generated on Fri May 16 2025 18:53:28 GMT+0000 (Coordinated Universal Time)
diff --git a/docs/src/use/integrations.md b/docs/src/use/integrations.md
index b050c906c3f1..548dc0e5194d 100644
--- a/docs/src/use/integrations.md
+++ b/docs/src/use/integrations.md
@@ -19,6 +19,9 @@ If you would like to recommend an integration to be added to this page, [submit
- Vim:
- [ALE](https://github.com/dense-analysis/ale)
- [Syntastic](https://github.com/vim-syntastic/syntastic/tree/master/syntax_checkers/javascript)
+- Neovim:
+ - [nvim-lspconfig](https://github.com/neovim/nvim-lspconfig/blob/master/doc/configs.md#eslint)
+ - [nvim-lint](https://github.com/mfussenegger/nvim-lint)
- Emacs: [Flycheck](http://www.flycheck.org/) supports ESLint with the [javascript-eslint](http://www.flycheck.org/en/latest/languages.html#javascript) checker.
- Eclipse Orion: ESLint is the [default linter](https://dev.eclipse.org/mhonarc/lists/orion-dev/msg02718.html)
- Eclipse IDE: [Tern ESLint linter](https://github.com/angelozerr/tern.java/wiki/Tern-Linter-ESLint)
diff --git a/docs/src/use/mcp.md b/docs/src/use/mcp.md
index ed20c9ea63c8..ece841cff7c2 100644
--- a/docs/src/use/mcp.md
+++ b/docs/src/use/mcp.md
@@ -23,7 +23,7 @@ Create a `.vscode/mcp.json` file in your project with the following configuratio
"ESLint": {
"type": "stdio",
"command": "npx",
- "args": ["eslint", "--mcp"]
+ "args": ["@eslint/mcp@latest"]
}
}
}
@@ -34,7 +34,7 @@ Alternatively, you can use the Command Palette:
1. Press `Ctrl+Shift+P` (Windows/Linux) or `Cmd+Shift+P` (macOS)
2. Type and select `MCP: Add Server`
3. Select `Command (stdio)` from the dropdown
-4. Enter `npx eslint --mcp` as the command
+4. Enter `npx @eslint/mcp@latest` as the command
5. Type `ESLint` as the server ID
6. Choose `Workspace Settings` to create the configuration in `.vscode/mcp.json`
@@ -76,7 +76,7 @@ Create a `.cursor/mcp.json` file in your project directory with the following co
"mcpServers": {
"eslint": {
"command": "npx",
- "args": ["eslint", "--mcp"],
+ "args": ["@eslint/mcp@latest"],
"env": {}
}
}
@@ -112,7 +112,7 @@ Add the following configuration to your `~/.codeium/windsurf/mcp_config.json` fi
"mcpServers": {
"eslint": {
"command": "npx",
- "args": ["eslint", "--mcp"],
+ "args": ["@eslint/mcp@latest"],
"env": {}
}
}
diff --git a/docs/src/use/suppressions.md b/docs/src/use/suppressions.md
index d24d3aeee081..5b75cd3a8752 100644
--- a/docs/src/use/suppressions.md
+++ b/docs/src/use/suppressions.md
@@ -47,7 +47,7 @@ eslint --suppressions-location .github/.eslint-suppressions
## Resolving Suppressions
-You can address any of the reported violations by making the necessary changes to the code as usual. If you run ESLint again you will notice that a warning is reported about unused suppressions. This is because the violations have been resolved but the suppressions are still in place.
+You can address any of the reported violations by making the necessary changes to the code as usual. If you run ESLint again you will notice that it exits with a non-zero exit code and an error is reported about unused suppressions. This is because the violations have been resolved but the suppressions are still in place.
```bash
> eslint
diff --git a/lib/cli-engine/cli-engine.js b/lib/cli-engine/cli-engine.js
index 3c9537cceb2f..a0c3bc67bfed 100644
--- a/lib/cli-engine/cli-engine.js
+++ b/lib/cli-engine/cli-engine.js
@@ -58,15 +58,15 @@ const validFixTypes = new Set(["directive", "problem", "suggestion", "layout"]);
//------------------------------------------------------------------------------
// For VSCode IntelliSense
-/** @typedef {import("../shared/types").ConfigData} ConfigData */
-/** @typedef {import("../shared/types").DeprecatedRuleInfo} DeprecatedRuleInfo */
-/** @typedef {import("../shared/types").LintMessage} LintMessage */
-/** @typedef {import("../shared/types").SuppressedLintMessage} SuppressedLintMessage */
-/** @typedef {import("../shared/types").ParserOptions} ParserOptions */
-/** @typedef {import("../shared/types").RuleConf} RuleConf */
-/** @typedef {import("../types").Rule.RuleModule} Rule */
+/** @typedef {import("../types").ESLint.ConfigData} ConfigData */
+/** @typedef {import("../types").ESLint.DeprecatedRuleUse} DeprecatedRuleInfo */
/** @typedef {import("../types").ESLint.FormatterFunction} FormatterFunction */
+/** @typedef {import("../types").Linter.LintMessage} LintMessage */
+/** @typedef {import("../types").Linter.ParserOptions} ParserOptions */
/** @typedef {import("../types").ESLint.Plugin} Plugin */
+/** @typedef {import("../types").Rule.RuleModule} Rule */
+/** @typedef {import("../types").Linter.RuleEntry} RuleConf */
+/** @typedef {import("../types").Linter.SuppressedLintMessage} SuppressedLintMessage */
/** @typedef {ReturnType} ConfigArray */
/** @typedef {ReturnType} ExtractedConfig */
diff --git a/lib/cli.js b/lib/cli.js
index b503587d92f9..e9133ab355ca 100644
--- a/lib/cli.js
+++ b/lib/cli.js
@@ -40,12 +40,13 @@ const debug = require("debug")("eslint:cli");
// Types
//------------------------------------------------------------------------------
-/** @typedef {import("./eslint/eslint").ESLintOptions} ESLintOptions */
-/** @typedef {import("./eslint/eslint").LintMessage} LintMessage */
-/** @typedef {import("./eslint/eslint").LintResult} LintResult */
+/** @import { ESLintOptions } from "./eslint/eslint.js" */
+
/** @typedef {import("./options").ParsedCLIOptions} ParsedCLIOptions */
-/** @typedef {import("./shared/types").ResultsMeta} ResultsMeta */
+/** @typedef {import("./types").Linter.LintMessage} LintMessage */
+/** @typedef {import("./types").ESLint.LintResult} LintResult */
/** @typedef {import("./types").ESLint.Plugin} Plugin */
+/** @typedef {import("./types").ESLint.ResultsMeta} ResultsMeta */
//------------------------------------------------------------------------------
// Helpers
diff --git a/lib/config/config-loader.js b/lib/config/config-loader.js
index 39908f79fa5b..3557f5cc8954 100644
--- a/lib/config/config-loader.js
+++ b/lib/config/config-loader.js
@@ -20,19 +20,17 @@ const { FlatConfigArray } = require("./flat-config-array");
// Types
//-----------------------------------------------------------------------------
-/**
- * @import { ConfigData, ConfigData as FlatConfigObject } from "../shared/types.js";
- */
+/** @typedef {import("../types").Linter.Config} Config */
/**
* @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} [defaultConfigs] The default configs to use.
+ * @property {Config|Array} [baseConfig] The base config to use.
+ * @property {Array} [defaultConfigs] The default configs to use.
* @property {Array} [ignorePatterns] The ignore patterns to use.
- * @property {FlatConfigObject|Array} [overrideConfig] The override config to use.
+ * @property {Config|Array} [overrideConfig] The override config to use.
* @property {boolean} [hasUnstableNativeNodeJsTSConfigFlag] The flag to indicate whether the `unstable_native_nodejs_ts_config` flag is enabled.
*/
@@ -394,8 +392,7 @@ class ConfigLoader {
* This is the same logic used by the ESLint CLI executable to determine
* configuration for each file it processes.
* @param {string} filePath The path of the file or directory to retrieve config for.
- * @returns {Promise} A configuration object for the file
- * or `undefined` if there is no configuration data for the file.
+ * @returns {Promise} A configuration object for the file.
* @throws {Error} If no configuration for `filePath` exists.
*/
async loadConfigArrayForFile(filePath) {
@@ -415,8 +412,7 @@ class ConfigLoader {
* This is the same logic used by the ESLint CLI executable to determine
* configuration for each file it processes.
* @param {string} dirPath The path of the directory to retrieve config for.
- * @returns {Promise} A configuration object for the directory
- * or `undefined` if there is no configuration data for the directory.
+ * @returns {Promise} A configuration object for the directory.
*/
async loadConfigArrayForDirectory(dirPath) {
assertValidFilePath(dirPath);
@@ -440,8 +436,7 @@ class ConfigLoader {
* intended to be used in locations where we know the config file has already
* been loaded and we just need to get the configuration for a file.
* @param {string} filePath The path of the file to retrieve a config object for.
- * @returns {ConfigData|undefined} A configuration object for the file
- * or `undefined` if there is no configuration data for the file.
+ * @returns {FlatConfigArray} A configuration object for the file.
* @throws {Error} If `filePath` is not a non-empty string.
* @throws {Error} If `filePath` is not an absolute path.
* @throws {Error} If the config file was not already loaded.
@@ -460,8 +455,7 @@ class ConfigLoader {
* intended to be used in locations where we know the config file has already
* been loaded and we just need to get the configuration for a file.
* @param {string} fileOrDirPath The path of the directory to retrieve a config object for.
- * @returns {ConfigData|undefined} A configuration object for the directory
- * or `undefined` if there is no configuration data for the directory.
+ * @returns {FlatConfigArray} A configuration object for the directory.
* @throws {Error} If `dirPath` is not a non-empty string.
* @throws {Error} If `dirPath` is not an absolute path.
* @throws {Error} If the config file was not already loaded.
@@ -789,8 +783,7 @@ class LegacyConfigLoader extends ConfigLoader {
* This is the same logic used by the ESLint CLI executable to determine
* configuration for each file it processes.
* @param {string} dirPath The path of the directory to retrieve config for.
- * @returns {Promise} A configuration object for the file
- * or `undefined` if there is no configuration data for the file.
+ * @returns {Promise} A configuration object for the file.
*/
async loadConfigArrayForDirectory(dirPath) {
assertValidFilePath(dirPath);
@@ -812,8 +805,7 @@ class LegacyConfigLoader extends ConfigLoader {
* intended to be used in locations where we know the config file has already
* been loaded and we just need to get the configuration for a file.
* @param {string} dirPath The path of the directory to retrieve a config object for.
- * @returns {ConfigData|undefined} A configuration object for the file
- * or `undefined` if there is no configuration data for the file.
+ * @returns {FlatConfigArray} A configuration object for the file.
* @throws {Error} If `dirPath` is not a non-empty string.
* @throws {Error} If `dirPath` is not an absolute path.
* @throws {Error} If the config file was not already loaded.
diff --git a/lib/config/config.js b/lib/config/config.js
index 74ddaad3f5b5..bb638bb32ca2 100644
--- a/lib/config/config.js
+++ b/lib/config/config.js
@@ -10,16 +10,31 @@
//-----------------------------------------------------------------------------
const { deepMergeArrays } = require("../shared/deep-merge-arrays");
-const { getRuleFromConfig } = require("./flat-config-helpers");
const { flatConfigSchema, hasMethod } = require("./flat-config-schema");
-const { RuleValidator } = require("./rule-validator");
const { ObjectSchema } = require("@eslint/config-array");
+const ajvImport = require("../shared/ajv");
+const ajv = ajvImport();
+const ruleReplacements = require("../../conf/replacements.json");
//-----------------------------------------------------------------------------
-// Helpers
+// Typedefs
+//-----------------------------------------------------------------------------
+
+/**
+ * @import { RuleDefinition } from "@eslint/core";
+ * @import { Linter } from "eslint";
+ */
+
//-----------------------------------------------------------------------------
+// Private Members
+//------------------------------------------------------------------------------
-const ruleValidator = new RuleValidator();
+// JSON schema that disallows passing any options
+const noOptionsSchema = Object.freeze({
+ type: "array",
+ minItems: 0,
+ maxItems: 0,
+});
const severities = new Map([
[0, 0],
@@ -30,6 +45,174 @@ const severities = new Map([
["error", 2],
]);
+/**
+ * A collection of compiled validators for rules that have already
+ * been validated.
+ * @type {WeakMap}
+ */
+const validators = new WeakMap();
+
+//-----------------------------------------------------------------------------
+// Helpers
+//-----------------------------------------------------------------------------
+
+/**
+ * Throws a helpful error when a rule cannot be found.
+ * @param {Object} ruleId The rule identifier.
+ * @param {string} ruleId.pluginName The ID of the rule to find.
+ * @param {string} ruleId.ruleName The ID of the rule to find.
+ * @param {Object} config The config to search in.
+ * @throws {TypeError} For missing plugin or rule.
+ * @returns {void}
+ */
+function throwRuleNotFoundError({ pluginName, ruleName }, config) {
+ const ruleId = pluginName === "@" ? ruleName : `${pluginName}/${ruleName}`;
+
+ const errorMessageHeader = `Key "rules": Key "${ruleId}"`;
+
+ let errorMessage = `${errorMessageHeader}: Could not find plugin "${pluginName}" in configuration.`;
+
+ const missingPluginErrorMessage = errorMessage;
+
+ // if the plugin exists then we need to check if the rule exists
+ if (config.plugins && config.plugins[pluginName]) {
+ const replacementRuleName = ruleReplacements.rules[ruleName];
+
+ if (pluginName === "@" && replacementRuleName) {
+ errorMessage = `${errorMessageHeader}: Rule "${ruleName}" was removed and replaced by "${replacementRuleName}".`;
+ } else {
+ errorMessage = `${errorMessageHeader}: Could not find "${ruleName}" in plugin "${pluginName}".`;
+
+ // otherwise, let's see if we can find the rule name elsewhere
+ for (const [otherPluginName, otherPlugin] of Object.entries(
+ config.plugins,
+ )) {
+ if (otherPlugin.rules && otherPlugin.rules[ruleName]) {
+ errorMessage += ` Did you mean "${otherPluginName}/${ruleName}"?`;
+ break;
+ }
+ }
+ }
+
+ // falls through to throw error
+ }
+
+ const error = new TypeError(errorMessage);
+
+ if (errorMessage === missingPluginErrorMessage) {
+ error.messageTemplate = "config-plugin-missing";
+ error.messageData = { pluginName, ruleId };
+ }
+
+ throw error;
+}
+
+/**
+ * The error type when a rule has an invalid `meta.schema`.
+ */
+class InvalidRuleOptionsSchemaError extends Error {
+ /**
+ * Creates a new instance.
+ * @param {string} ruleId Id of the rule that has an invalid `meta.schema`.
+ * @param {Error} processingError Error caught while processing the `meta.schema`.
+ */
+ constructor(ruleId, processingError) {
+ super(
+ `Error while processing options validation schema of rule '${ruleId}': ${processingError.message}`,
+ { cause: processingError },
+ );
+ this.code = "ESLINT_INVALID_RULE_OPTIONS_SCHEMA";
+ }
+}
+
+/**
+ * Parses a ruleId into its plugin and rule parts.
+ * @param {string} ruleId The rule ID to parse.
+ * @returns {{pluginName:string,ruleName:string}} The plugin and rule
+ * parts of the ruleId;
+ */
+function parseRuleId(ruleId) {
+ let pluginName, ruleName;
+
+ // distinguish between core rules and plugin rules
+ if (ruleId.includes("/")) {
+ // mimic scoped npm packages
+ if (ruleId.startsWith("@")) {
+ pluginName = ruleId.slice(0, ruleId.lastIndexOf("/"));
+ } else {
+ pluginName = ruleId.slice(0, ruleId.indexOf("/"));
+ }
+
+ ruleName = ruleId.slice(pluginName.length + 1);
+ } else {
+ pluginName = "@";
+ ruleName = ruleId;
+ }
+
+ return {
+ pluginName,
+ ruleName,
+ };
+}
+
+/**
+ * Retrieves a rule instance from a given config based on the ruleId.
+ * @param {string} ruleId The rule ID to look for.
+ * @param {Linter.Config} config The config to search.
+ * @returns {RuleDefinition|undefined} The rule if found
+ * or undefined if not.
+ */
+function getRuleFromConfig(ruleId, config) {
+ const { pluginName, ruleName } = parseRuleId(ruleId);
+
+ return config.plugins?.[pluginName]?.rules?.[ruleName];
+}
+
+/**
+ * Gets a complete options schema for a rule.
+ * @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`.
+ */
+function getRuleOptionsSchema(rule) {
+ if (!rule.meta) {
+ return { ...noOptionsSchema }; // default if `meta.schema` is not specified
+ }
+
+ const schema = rule.meta.schema;
+
+ if (typeof schema === "undefined") {
+ return { ...noOptionsSchema }; // default if `meta.schema` is not specified
+ }
+
+ // `schema:false` is an allowed explicit opt-out of options validation for the rule
+ if (schema === false) {
+ return null;
+ }
+
+ if (typeof schema !== "object" || schema === null) {
+ throw new TypeError("Rule's `meta.schema` must be an array or object");
+ }
+
+ // ESLint-specific array form needs to be converted into a valid JSON Schema definition
+ if (Array.isArray(schema)) {
+ if (schema.length) {
+ return {
+ type: "array",
+ items: schema,
+ minItems: 0,
+ maxItems: schema.length,
+ };
+ }
+
+ // `schema:[]` is an explicit way to specify that the rule does not accept any options
+ return { ...noOptionsSchema };
+ }
+
+ // `schema:
