Add ESLint 9 support and migrate to flat config

.nvmrc

@@ -1 +1 @@
-18.13
+20

__tests__/__snapshots__/check-fixtures.js.snap

@@ -48,6 +48,22 @@ exports[`linting javascript.js fixture matches snapshot 1`] = `
     "nodeType": "Identifier",
     "ruleId": "no-unused-vars",
     "severity": 2,
+    "suggestions": [
+      {
+        "data": {
+          "varName": "unusedEs6Import",
+        },
+        "desc": "Remove unused variable 'unusedEs6Import'.",
+        "fix": {
+          "range": [
+            0,
+            57,
+          ],
+          "text": "",
+        },
+        "messageId": "removeVar",
+      },
+    ],
   },
   {
     "column": 1,
@@ -110,6 +126,22 @@ import { unusedEs6Import } from './stub/unusedEs6Import';
     "nodeType": "Identifier",
     "ruleId": "no-unused-vars",
     "severity": 2,
+    "suggestions": [
+      {
+        "data": {
+          "varName": "y",
+        },
+        "desc": "Remove unused variable 'y'.",
+        "fix": {
+          "range": [
+            365,
+            366,
+          ],
+          "text": "",
+        },
+        "messageId": "removeVar",
+      },
+    ],
   },
   {
     "column": 9,
@@ -176,6 +208,7 @@ import { unusedEs6Import } from './stub/unusedEs6Import';
     "endLine": 38,
     "line": 36,
     "message": "Avoid passing an async function to Array.prototype.forEach",
+    "messageId": "avoidAsyncForEach",
     "nodeType": "ExpressionStatement",
     "ruleId": "@automattic/wpvip/no-async-foreach",
     "severity": 2,
@@ -203,8 +236,8 @@ import { unusedEs6Import } from './stub/unusedEs6Import';
       "text": "Boolean('heyyy')",
     },
     "line": 47,
-    "message": "use \`Boolean('heyyy')\` instead.",
-    "messageId": "useRecommendation",
+    "message": "Unexpected implicit coercion encountered. Use \`Boolean('heyyy')\` instead.",
+    "messageId": "implicitCoercion",
     "nodeType": "UnaryExpression",
     "ruleId": "no-implicit-coercion",
     "severity": 2,
@@ -280,17 +313,6 @@ exports[`linting typescript.ts fixture matches snapshot 1`] = `
     "ruleId": "import/order",
     "severity": 2,
   },
-  {
-    "column": 10,
-    "endColumn": 25,
-    "endLine": 1,
-    "line": 1,
-    "message": "'unusedEs6Import' is defined but never used.",
-    "messageId": "unusedVar",
-    "nodeType": null,
-    "ruleId": "@typescript-eslint/no-unused-vars",
-    "severity": 2,
-  },
   {
     "column": 10,
     "endColumn": 25,
@@ -309,6 +331,17 @@ exports[`linting typescript.ts fixture matches snapshot 1`] = `
     "ruleId": "unused-imports/no-unused-imports",
     "severity": 1,
   },
+  {
+    "column": 10,
+    "endColumn": 25,
+    "endLine": 1,
+    "line": 1,
+    "message": "'unusedEs6Import' is defined but never used.",
+    "messageId": "unusedVar",
+    "nodeType": null,
+    "ruleId": "@typescript-eslint/no-unused-vars",
+    "severity": 2,
+  },
   {
     "column": 1,
     "endColumn": 38,
@@ -351,10 +384,10 @@ import { unusedEs6Import } from './stub/unusedEs6Import';
       "text": "string",
     },
     "line": 4,
-    "message": "Don't use \`String\` as a type. Use string instead",
-    "messageId": "bannedTypeMessage",
+    "message": "Prefer using the primitive \`string\` as a type name, rather than the upper-cased \`String\`.",
+    "messageId": "bannedClassType",
     "nodeType": "Identifier",
-    "ruleId": "@typescript-eslint/ban-types",
+    "ruleId": "@typescript-eslint/no-wrapper-object-types",
     "severity": 2,
   },
   {
@@ -386,7 +419,7 @@ import { unusedEs6Import } from './stub/unusedEs6Import';
     "endColumn": 24,
     "endLine": 16,
     "line": 16,
-    "message": "Unsafe return of an \`any\` typed value.",
+    "message": "Unsafe return of a value of type \`any\`.",
     "messageId": "unsafeReturn",
     "nodeType": "Identifier",
     "ruleId": "@typescript-eslint/no-unsafe-return",
@@ -589,6 +622,7 @@ import { unusedEs6Import } from './stub/unusedEs6Import';
     "endLine": 67,
     "line": 67,
     "message": "@Controller should not have route prefixes.",
+    "messageId": "controllerPrefix",
     "nodeType": "Decorator",
     "ruleId": "@automattic/wpvip/nestjs-route-prefix",
     "severity": 2,

__tests__/check-fixtures.js

@@ -5,8 +5,8 @@ async function getLintMessages( fixture ) {
 	const rootPaths = [ __dirname, '..' ];
 	const eslint = new ESLint( {
 		ignore: false,
-		overrideConfigFile: path.resolve( ...rootPaths, '.eslintrc.js' ),
-		useEslintrc: false,
+		overrideConfigFile: path.resolve( ...rootPaths, 'eslint.config.js' ),
+		baseConfig: null,
 	} );
 
 	const [ { messages } ] = await eslint.lintFiles(

__tests__/rules/nestjs-route-prefix.ts

@@ -1,15 +1,19 @@
-/**
- * External dependencies
- */
-import { Linter, RuleTester } from 'eslint';
+import * as tsEsLintParser from '@typescript-eslint/parser';
+import { type Linter, RuleTester } from 'eslint';
 
-/**
- * Internal dependencies
- */
 import rule from '../../rules/nestjs-route-prefix';
 
-const ruleTester = new RuleTester( { parser: require.resolve( '@typescript-eslint/parser' ) } );
-const parserOptions: Linter.ParserOptions = { ecmaVersion: 8 };
+const languageOptions: Linter.LanguageOptions = {
+	ecmaVersion: 'latest',
+	parser: tsEsLintParser,
+	parserOptions: {
+		ecmaVersion: 'latest',
+	},
+};
+
+const ruleTester = new RuleTester( {
+	languageOptions,
+} );
 
 describe( 'nestjs-routes', () => {
 	ruleTester.run( 'nestjs-routes', rule, {
@@ -19,28 +23,24 @@ describe( 'nestjs-routes', () => {
 				@Get('/hello/w*d')
 				export class CustomController {}
 				`,
-				parserOptions,
 			},
 			{
 				code: `
 				@Get('/:id')
 				export class CustomController {}
 				`,
-				parserOptions,
 			},
 			{
 				code: `
 				@Controller()
 				export class CustomController {}
 				`,
-				parserOptions,
 			},
 			{
 				code: `
 				@Controller({ host: 'example.org' })
 				export class CustomController {}
 				`,
-				parserOptions,
 			},
 		],
 		invalid: [
@@ -49,48 +49,35 @@ describe( 'nestjs-routes', () => {
 				@Controller('/v1')
 				export class CustomController {}
 				`,
-				errors: [ { message: '@Controller should not have route prefixes.' } ],
-				parserOptions,
+				errors: [ { messageId: 'controllerPrefix' } ],
 			},
 			{
 				code: `
 				@Get('hello/world/')
 				export class CustomController {}
 				`,
-				errors: [
-					{ message: "@Get should have a route starting with '/' and not ending with '/'." },
-				],
-				parserOptions,
+				errors: [ { messageId: 'decoratorSlash', data: { decoratorName: 'Get' } } ],
 			},
 			{
 				code: `
 				@Get('')
 				export class CustomController {}
 				`,
-				errors: [
-					{ message: "@Get should have a route starting with '/' and not ending with '/'." },
-				],
-				parserOptions,
+				errors: [ { messageId: 'decoratorSlash', data: { decoratorName: 'Get' } } ],
 			},
 			{
 				code: `
 				@Post('/hello/world/')
 				export class CustomController {}
 				`,
-				errors: [
-					{ message: "@Post should have a route starting with '/' and not ending with '/'." },
-				],
-				parserOptions,
+				errors: [ { messageId: 'decoratorSlash', data: { decoratorName: 'Post' } } ],
 			},
 			{
 				code: `
 				@Get(':id')
 				export class CustomController {}
 				`,
-				errors: [
-					{ message: "@Get should have a route starting with '/' and not ending with '/'." },
-				],
-				parserOptions,
+				errors: [ { messageId: 'decoratorSlash', data: { decoratorName: 'Get' } } ],
 			},
 		],
 	} );

__tests__/rules/no-async-foreach.ts

@@ -1,39 +1,34 @@
-/**
- * External dependencies
- */
 import { Linter, RuleTester } from 'eslint';
 
-/**
- * Internal dependencies
- */
+/** @type {import('eslint').Rule.RuleModule} */
 import rule from '../../rules/no-async-foreach';
 
 const ruleTester = new RuleTester();
-const parserOptions: Linter.ParserOptions = { ecmaVersion: 8 };
-const errors = [ { message: 'Avoid passing an async function to Array.prototype.forEach' } ];
+const languageOptions: Linter.LanguageOptions = { ecmaVersion: 8 };
+const errors = [ { messageId: 'avoidAsyncForEach' } ];
 
 describe( 'no-async-foreach', () => {
 	ruleTester.run( 'no-async-foreach', rule, {
 		valid: [
 			{
 				code: '[].forEach(() => {})',
-				parserOptions,
+				languageOptions,
 			},
 			{
 				code: '[].forEach(function() {})',
-				parserOptions,
+				languageOptions,
 			},
 		],
 		invalid: [
 			{
 				code: '[].forEach(async () => {})',
 				errors,
-				parserOptions,
+				languageOptions,
 			},
 			{
 				code: '[].forEach(async function() {})',
 				errors,
-				parserOptions,
+				languageOptions,
 			},
 		],
 	} );

configs/cli.js

@@ -1,13 +1,16 @@
-module.exports = {
-	/**
-	 * Please include a short description of the rule. For rules that downgrade or
-	 * disable errors, include a brief justification or reasoning.
-	 */
-	rules: {
-		// Allow child_process and non-literal `exec` arguments.
-		'security/detect-child-process': 'off',
+/** @type import('eslint').Linter.Config[] */
+module.exports = [
+	{
+		/**
+		 * Please include a short description of the rule. For rules that downgrade or
+		 * disable errors, include a brief justification or reasoning.
+		 */
+		rules: {
+			// Allow child_process and non-literal `exec` arguments.
+			'security/detect-child-process': 'off',
 
-		// Process.exit is used in CLI context to stop execution.
-		'no-process-exit': 'off',
+			// Process.exit is used in CLI context to stop execution.
+			'no-process-exit': 'off',
+		},
 	},
-};
+];