feat: add eslint-plugin-regexp to eslint-config-eslint base config (#19951)

Pixel998 · web-flow · commit 43a5f9e36f1a · 2025-08-14T12:07:23.000-04:00
* feat: add eslint-plugin-regexp to eslint-config-eslint base config

* resolve linting errors

* apply fasttime's suggestions

* revert regex change and suppress false positive

* update eslint-plugin-regexp

* remove start anchor from plugin member name regex
diff --git a/docs/tools/markdown-it-rule-example.js b/docs/tools/markdown-it-rule-example.js
@@ -73,7 +73,7 @@ function markdownItRuleExample({ open, close }) {
 			}
 
 			const { type, languageOptionsJSON } =
-				/^\s*(?<type>\S+)(\s+(?<languageOptionsJSON>\S.*?))?\s*$/u.exec(
+				/^\s*(?<type>\S+)(?:\s+(?<languageOptionsJSON>\S(?:.*\S)?))?/u.exec(
 					tagToken.info,
 				).groups;
 			const languageOptions = languageOptionsJSON
diff --git a/lib/cli-engine/file-enumerator.js b/lib/cli-engine/file-enumerator.js
@@ -51,7 +51,7 @@ const debug = require("debug")("eslint:file-enumerator");
 //------------------------------------------------------------------------------
 
 const minimatchOpts = { dot: true, matchBase: true };
-const dotfilesPattern = /(?:(?:^\.)|(?:[/\\]\.))[^/\\.].*/u;
+const dotfilesPattern = /(?:^\.|[/\\]\.)[^/\\.].*/u;
 const NONE = 0;
 const IGNORED_SILENTLY = 1;
 const IGNORED = 2;
diff --git a/lib/config/flat-config-schema.js b/lib/config/flat-config-schema.js
@@ -230,7 +230,7 @@ function assertIsRuleSeverity(ruleId, value) {
  * @throws {TypeError} If the string isn't in the correct format.
  */
 function assertIsPluginMemberName(value) {
-	if (!/[@a-z0-9-_$]+(?:\/(?:[a-z0-9-_$]+))+$/iu.test(value)) {
+	if (!/[\w\-@$]+(?:\/[\w\-$]+)+$/iu.test(value)) {
 		throw new TypeError(
 			`Expected string in the form "pluginName/objectName" but found "${value}".`,
 		);
diff --git a/lib/languages/js/source-code/source-code.js b/lib/languages/js/source-code/source-code.js
@@ -1056,7 +1056,7 @@ class SourceCode extends TokenStore {
 			// only certain comment types are supported as line comments
 			return (
 				comment.type !== "Line" ||
-				!!/^eslint-disable-(next-)?line$/u.test(directive.label)
+				!!/^eslint-disable-(?:next-)?line$/u.test(directive.label)
 			);
 		});
 
@@ -1091,9 +1091,8 @@ class SourceCode extends TokenStore {
 			} = commentParser.parseDirective(comment.value);
 
 			// Step 2: Extract the directive value
-			const lineCommentSupported = /^eslint-disable-(next-)?line$/u.test(
-				label,
-			);
+			const lineCommentSupported =
+				/^eslint-disable-(?:next-)?line$/u.test(label);
 
 			if (comment.type === "Line" && !lineCommentSupported) {
 				return;
diff --git a/lib/linter/interpolate.js b/lib/linter/interpolate.js
@@ -14,7 +14,7 @@
  * @returns {RegExp} Global regular expression matching placeholders
  */
 function getPlaceholderMatcher() {
-	return /\{\{([^{}]+?)\}\}/gu;
+	return /\{\{([^{}]+)\}\}/gu;
 }
 
 /**
diff --git a/lib/linter/linter.js b/lib/linter/linter.js
@@ -438,9 +438,8 @@ function getDirectiveComments(
 				justification: justificationPart,
 			} = directive;
 
-			const lineCommentSupported = /^eslint-disable-(next-)?line$/u.test(
-				label,
-			);
+			const lineCommentSupported =
+				/^eslint-disable-(?:next-)?line$/u.test(label);
 
 			if (comment.type === "Line" && !lineCommentSupported) {
 				return;
@@ -739,7 +738,7 @@ function normalizeEcmaVersionForLanguageOptions(ecmaVersion) {
 	return LATEST_ECMA_VERSION;
 }
 
-const eslintEnvPattern = /\/\*\s*eslint-env\s(.+?)(?:\*\/|$)/gsu;
+const eslintEnvPattern = /\/\*\s*eslint-env\s.+?(?:\*\/|$)/gsu;
 
 /**
  * Checks whether or not there is a comment which has "eslint-env *" in a given text.
diff --git a/lib/rules/dot-notation.js b/lib/rules/dot-notation.js
@@ -15,7 +15,7 @@ const keywords = require("./utils/keywords");
 // Rule Definition
 //------------------------------------------------------------------------------
 
-const validIdentifier = /^[a-zA-Z_$][a-zA-Z0-9_$]*$/u;
+const validIdentifier = /^[a-zA-Z_$][\w$]*$/u;
 
 // `null` literal must be handled separately.
 const literalTypesToCheck = new Set(["string", "boolean"]);
diff --git a/lib/rules/indent-legacy.js b/lib/rules/indent-legacy.js
@@ -1162,7 +1162,7 @@ module.exports = {
 		 * @returns {boolean} the result
 		 */
 		function isWrappedInParenthesis(node) {
-			const regex = /^return\s*?\(\s*?\);*?/u;
+			const regex = /^return\s*\(\s*\)/u;
 
 			const statementWithoutArgument = sourceCode
 				.getText(node)
diff --git a/lib/rules/no-alert.js b/lib/rules/no-alert.js
@@ -24,7 +24,7 @@ const {
  * @returns {boolean} Whether or not the name is prohibited.
  */
 function isProhibitedIdentifier(name) {
-	return /^(alert|confirm|prompt)$/u.test(name);
+	return /^(?:alert|confirm|prompt)$/u.test(name);
 }
 
 /**
diff --git a/lib/rules/no-empty-function.js b/lib/rules/no-empty-function.js
@@ -162,7 +162,7 @@ module.exports = {
 				}
 			}
 
-			if (/(g|s)etters|methods$/iu.test(kind)) {
+			if (/(?:g|s)etters|methods$/iu.test(kind)) {
 				if (
 					(node.parent.decorators?.length &&
 						allow.includes("decoratedFunctions")) ||
diff --git a/lib/rules/no-irregular-whitespace.js b/lib/rules/no-irregular-whitespace.js
@@ -19,8 +19,8 @@ const astUtils = require("./utils/ast-utils");
 const ALL_IRREGULARS =
 	/[\f\v\u0085\ufeff\u00a0\u1680\u180e\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u200b\u202f\u205f\u3000\u2028\u2029]/u;
 const IRREGULAR_WHITESPACE =
-	/[\f\v\u0085\ufeff\u00a0\u1680\u180e\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u200b\u202f\u205f\u3000]+/gmu;
-const IRREGULAR_LINE_TERMINATORS = /[\u2028\u2029]/gmu;
+	/[\f\v\u0085\ufeff\u00a0\u1680\u180e\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u200b\u202f\u205f\u3000]+/gu;
+const IRREGULAR_LINE_TERMINATORS = /[\u2028\u2029]/gu;
 const LINE_BREAK = astUtils.createGlobalLinebreakMatcher();
 
 //------------------------------------------------------------------------------
diff --git a/lib/rules/no-mixed-spaces-and-tabs.js b/lib/rules/no-mixed-spaces-and-tabs.js
@@ -99,6 +99,7 @@ module.exports = {
 					 * At least one space followed by a tab
 					 * before non-tab/-space characters begin.
 					 */
+					// eslint-disable-next-line regexp/no-empty-lookarounds-assertion -- False positive
 					regex = /^(?=(\t*))\1(?=( +))\2\t/u;
 				}
 
diff --git a/lib/rules/no-octal.js b/lib/rules/no-octal.js
@@ -30,10 +30,7 @@ module.exports = {
 	create(context) {
 		return {
 			Literal(node) {
-				if (
-					typeof node.value === "number" &&
-					/^0[0-9]/u.test(node.raw)
-				) {
+				if (typeof node.value === "number" && /^0\d/u.test(node.raw)) {
 					context.report({
 						node,
 						messageId: "noOctal",
diff --git a/lib/rules/no-trailing-spaces.js b/lib/rules/no-trailing-spaces.js
@@ -82,7 +82,8 @@ module.exports = {
 	create(context) {
 		const sourceCode = context.sourceCode;
 
-		const BLANK_CLASS = "[ \t\u00a0\u2000-\u200b\u3000]",
+		const BLANK_CLASS =
+				"[ \t\u00a0\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u200b\u3000]",
 			SKIP_BLANK = `^${BLANK_CLASS}*$`,
 			NONBLANK = `${BLANK_CLASS}+$`;
 
diff --git a/lib/rules/no-useless-escape.js b/lib/rules/no-useless-escape.js
@@ -387,7 +387,7 @@ module.exports = {
 				const value = isTemplateElement
 					? sourceCode.getText(node)
 					: node.raw;
-				const pattern = /\\[^\d]/gu;
+				const pattern = /\\\D/gu;
 				let match;
 
 				while ((match = pattern.exec(value))) {
diff --git a/lib/rules/prefer-regex-literals.js b/lib/rules/prefer-regex-literals.js
@@ -522,7 +522,7 @@ module.exports = {
 						}
 
 						if (
-							!/^[-a-zA-Z0-9\\[\](){} \t\r\n\v\f!@#$%^&*+^_=/~`.><?,'"|:;]*$/u.test(
+							!/^[-\w\\[\](){} \t\r\n\v\f!@#$%^&*+=/~`.><?,'"|:;]*$/u.test(
 								regexContent,
 							)
 						) {
diff --git a/lib/rules/utils/ast-utils.js b/lib/rules/utils/ast-utils.js
@@ -58,7 +58,7 @@ const DECIMAL_INTEGER_PATTERN = /^(?:0|0[0-7]*[89]\d*|[1-9](?:_?\d)*)$/u;
 
 // Tests the presence of at least one LegacyOctalEscapeSequence or NonOctalDecimalEscapeSequence in a raw string
 const OCTAL_OR_NON_OCTAL_DECIMAL_ESCAPE_PATTERN =
-	/^(?:[^\\]|\\.)*\\(?:[1-9]|0[0-9])/su;
+	/^(?:[^\\]|\\.)*\\(?:[1-9]|0\d)/su;
 
 const LOGICAL_ASSIGNMENT_OPERATORS = new Set(["&&=", "||=", "??="]);
 
diff --git a/lib/rules/utils/char-source.js b/lib/rules/utils/char-source.js
@@ -85,7 +85,7 @@ function readHexSequence(reader, length) {
  * @returns {string} A code unit.
  */
 function readUnicodeSequence(reader) {
-	const regExp = /\{(?<hexDigits>[\dA-Fa-f]+)\}/uy;
+	const regExp = /\{(?<hexDigits>[\dA-F]+)\}/iuy;
 
 	regExp.lastIndex = reader.pos;
 	const match = regExp.exec(reader.source);
diff --git a/lib/rules/yoda.js b/lib/rules/yoda.js
@@ -20,7 +20,7 @@ const astUtils = require("./utils/ast-utils");
  * @returns {boolean} Whether or not it is a comparison operator.
  */
 function isComparisonOperator(operator) {
-	return /^(==|===|!=|!==|<|>|<=|>=)$/u.test(operator);
+	return /^(?:==|===|!=|!==|<|>|<=|>=)$/u.test(operator);
 }
 
 /**
@@ -29,7 +29,7 @@ function isComparisonOperator(operator) {
  * @returns {boolean} Whether or not it is an equality operator.
  */
 function isEqualityOperator(operator) {
-	return /^(==|===)$/u.test(operator);
+	return /^(?:==|===)$/u.test(operator);
 }
 
 /**
diff --git a/lib/shared/naming.js b/lib/shared/naming.js
@@ -4,7 +4,7 @@
 
 "use strict";
 
-const NAMESPACE_REGEX = /^@.*\//iu;
+const NAMESPACE_REGEX = /^@.*\//u;
 
 /**
  * Brings package name to correct format based on prefix
diff --git a/packages/eslint-config-eslint/base.js b/packages/eslint-config-eslint/base.js
@@ -4,6 +4,7 @@ const js = require("@eslint/js");
 const jsdoc = require("eslint-plugin-jsdoc");
 const eslintCommentsPluginConfigs = require("@eslint-community/eslint-plugin-eslint-comments/configs");
 const unicorn = require("eslint-plugin-unicorn");
+const regexp = require("eslint-plugin-regexp");
 
 // extends eslint recommended config
 /**
@@ -294,6 +295,12 @@ const eslintCommentsConfigs = [
 	},
 ];
 
+// extends eslint-plugin-regexp's recommended config
+/**
+ * @type {import("eslint").Linter.Config[]}
+ */
+const regexpConfigs = [regexp.configs["flat/recommended"]];
+
 /**
  * @type {import("eslint").Linter.Config[]}
  */
@@ -305,8 +312,9 @@ module.exports = [
 			reportUnusedInlineConfigs: "error",
 		},
 	},
-	...jsConfigs,
 	...unicornConfigs,
 	...jsdocConfigs,
 	...eslintCommentsConfigs,
+	...regexpConfigs,
+	...jsConfigs,
 ];
diff --git a/packages/eslint-config-eslint/package.json b/packages/eslint-config-eslint/package.json
@@ -66,6 +66,7 @@
     "@eslint/js": "^9.0.0",
     "eslint-plugin-jsdoc": "^48.2.3",
     "eslint-plugin-n": "^17.11.1",
+    "eslint-plugin-regexp": "^2.10.0",
     "eslint-plugin-unicorn": "^52.0.0"
   },
   "devDependencies": {
diff --git a/tests/lib/linter/code-path-analysis/code-path-analyzer.js b/tests/lib/linter/code-path-analysis/code-path-analyzer.js
@@ -21,8 +21,8 @@ const assert = require("node:assert"),
 // Helpers
 //------------------------------------------------------------------------------
 
-const expectedPattern = /\/\*expected\s+((?:.|[\r\n])+?)\s*\*\//gu;
-const languageOptionsPattern = /\/\*languageOptions\s+((?:.|[\r\n])+?)\s*\*\//u;
+const expectedPattern = /\/\*expected\s((?:.|[\r\n])+?)\*\//gu;
+const languageOptionsPattern = /\/\*languageOptions\s((?:.|[\r\n])+?)\*\//u;
 const lineEndingPattern = /\r?\n/gu;
 const linter = new Linter();
 
@@ -39,7 +39,7 @@ function getExpectedDotArrows(source) {
 	let m;
 
 	while ((m = expectedPattern.exec(source)) !== null) {
-		retv.push(m[1].replace(lineEndingPattern, "\n"));
+		retv.push(m[1].trim().replace(lineEndingPattern, "\n"));
 	}
 
 	return retv;
diff --git a/tests/lib/rules/utils/ast-utils.js b/tests/lib/rules/utils/ast-utils.js
@@ -2152,12 +2152,12 @@ describe("ast-utils", () => {
 				{
 					nodeA: {
 						type: "Literal",
-						value: /(?:)/u,
+						value: /(?:)/u, // eslint-disable-line regexp/no-empty-group -- Test data for regex comparison
 						regex: { pattern: "(?:)", flags: "u" },
 					},
 					nodeB: {
 						type: "Literal",
-						value: /(?:)/u,
+						value: /(?:)/u, // eslint-disable-line regexp/no-empty-group -- Test data for regex comparison
 						regex: { pattern: "(?:)", flags: "u" },
 					},
 					expected: true,
@@ -2183,7 +2183,7 @@ describe("ast-utils", () => {
 					},
 					nodeB: {
 						type: "Literal",
-						value: /(?:)/, // eslint-disable-line require-unicode-regexp -- Checking non-Unicode regex
+						value: /(?:)/, // eslint-disable-line require-unicode-regexp, regexp/no-empty-group -- Checking non-Unicode regex
 						regex: { pattern: "(?:)", flags: "" },
 					},
 					expected: false,
diff --git a/tests/lib/shared/runtime-info.js b/tests/lib/shared/runtime-info.js
@@ -222,7 +222,7 @@ describe("RuntimeInfo", () => {
 
 			assert.throws(
 				RuntimeInfo.environment,
-				/^Unexpected token .*T.* JSON/u,
+				/^Unexpected token [^\n\rT\u2028\u2029]*T.* JSON/u,
 			);
 			assert.strictEqual(
 				logErrorStub.args[0][0],
@@ -236,7 +236,7 @@ describe("RuntimeInfo", () => {
 
 			assert.throws(
 				RuntimeInfo.environment,
-				/^Unexpected token .*T.* JSON/u,
+				/^Unexpected token [^\n\rT\u2028\u2029]*T.* JSON/u,
 			);
 			assert.strictEqual(
 				logErrorStub.args[0][0],
diff --git a/tools/update-readme.js b/tools/update-readme.js
@@ -122,15 +122,15 @@ const HTML_TEMPLATE = stripIndents`
 
 	// replace all of the section
 	let newReadme = readme.replace(
-		/<!--teamstart-->[\w\W]*?<!--teamend-->/u,
+		/<!--teamstart-->[\s\S]*?<!--teamend-->/u,
 		ejs.render(HTML_TEMPLATE, {
 			team,
 			formatTeamMembers,
 		}),
 	);
 
 	newReadme = newReadme.replace(
-		/<!--sponsorsstart-->[\w\W]*?<!--sponsorsend-->/u,
+		/<!--sponsorsstart-->[\s\S]*?<!--sponsorsend-->/u,
 		`<!--sponsorsstart-->\n\n${allSponsors}\n\n<!--sponsorsend-->`,
 	);
 
diff --git a/tools/update-rule-type-headers.js b/tools/update-rule-type-headers.js
@@ -191,7 +191,7 @@ function getTextPositionsMap(sourceText, consideredRuleIds) {
  */
 function paraphraseDescription(description) {
 	let newDescription;
-	const match = /^(Disallow|Enforce|Require) /u.exec(description);
+	const match = /^(?:Disallow|Enforce|Require) /u.exec(description);
 
 	if (match) {
 		newDescription = `Rule to ${description[0].toLowerCase()}${description.slice(1)}`;

Original file line number	Diff line number	Diff line change
`@@ -73,7 +73,7 @@ function markdownItRuleExample({ open, close }) {`
`73`	`73`	`}`
`74`	`74`
`75`	`75`	`const { type, languageOptionsJSON } =`
`76`		`- /^\s(?<type>\S+)(\s+(?<languageOptionsJSON>\S.?))?\s*$/u.exec(`
	`76`	`+ /^\s(?<type>\S+)(?:\s+(?<languageOptionsJSON>\S(?:.\S)?))?/u.exec(`
`77`	`77`	`tagToken.info,`
`78`	`78`	`).groups;`
`79`	`79`	`const languageOptions = languageOptionsJSON`
Original file line number	Diff line number	Diff line change
`@@ -14,7 +14,7 @@`
`14`	`14`	`* @returns {RegExp} Global regular expression matching placeholders`
`15`	`15`	`*/`
`16`	`16`	`function getPlaceholderMatcher() {`
`17`		`- return /\{\{([^{}]+?)\}\}/gu;`
	`17`	`+ return /\{\{([^{}]+)\}\}/gu;`
`18`	`18`	`}`
`19`	`19`
`20`	`20`	`/**`
Original file line number	Diff line number	Diff line change
`@@ -24,7 +24,7 @@ const {`
`24`	`24`	`* @returns {boolean} Whether or not the name is prohibited.`
`25`	`25`	`*/`
`26`	`26`	`function isProhibitedIdentifier(name) {`
`27`		`- return /^(alert\|confirm\|prompt)$/u.test(name);`
	`27`	`+ return /^(?:alert\|confirm\|prompt)$/u.test(name);`
`28`	`28`	`}`
`29`	`29`
`30`	`30`	`/**`
Original file line number	Diff line number	Diff line change
`@@ -162,7 +162,7 @@ module.exports = {`
`162`	`162`	`}`
`163`	`163`	`}`
`164`	`164`
`165`		`- if (/(g\|s)etters\|methods$/iu.test(kind)) {`
	`165`	`+ if (/(?:g\|s)etters\|methods$/iu.test(kind)) {`
`166`	`166`	`if (`
`167`	`167`	`(node.parent.decorators?.length &&`
`168`	`168`	`allow.includes("decoratedFunctions")) \|\|`