typescript-eslint · JoshuaKGoldberg · May 12, 2024 · Apr 26, 2024 · Apr 26, 2024 · Apr 28, 2024
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -134,6 +134,25 @@ jobs:
         run: yarn stylelint
         working-directory: packages/website
 
+  eslint_v9_tests:
+    name: Run tests on ESLint v9
+    needs: [build]
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Install
+        uses: ./.github/actions/prepare-install
+        with:
+          node-version: ${{ env.PRIMARY_NODE_VERSION }}
+      - name: Build
+        uses: ./.github/actions/prepare-build
+      - run: yarn add eslint@9
+      - name: Run tests
+        run: yarn test
+        env:
+          CI: true
+
   integration_tests:
     name: Run integration tests on primary Node.js version
     needs: [build]

diff --git a/.../VariableDeclaration/fixtures/_error_/missing-value-in-using/snapshots/2-Babel-Error.shot b/.../VariableDeclaration/fixtures/_error_/missing-value-in-using/snapshots/2-Babel-Error.shot
diff --git a/...iableDeclaration/fixtures/_error_/missing-value-in-using/snapshots/3-Alignment-Error.shot b/...iableDeclaration/fixtures/_error_/missing-value-in-using/snapshots/3-Alignment-Error.shot
diff --git a/packages/ast-spec/tests/fixtures-with-differences-errors.shot b/packages/ast-spec/tests/fixtures-with-differences-errors.shot
diff --git a/packages/eslint-plugin/package.json b/packages/eslint-plugin/package.json
@@ -103,7 +103,7 @@
   },
   "peerDependencies": {
     "@typescript-eslint/parser": "^7.0.0",
-    "eslint": "^8.57.0"
+    "eslint": "^8.57.0 || ^9.0.0"
   },
   "peerDependenciesMeta": {
     "typescript": {

diff --git a/packages/eslint-plugin/tests/docs.test.ts b/packages/eslint-plugin/tests/docs.test.ts
@@ -100,7 +100,7 @@ function renderLintResults(code: string, errors: Linter.LintMessage[]): string {
   return output.join('\n').trim() + '\n';
 }
 
-const linter = new Linter();
+const linter = new Linter({ configType: 'eslintrc' });
 linter.defineParser('@typescript-eslint/parser', tseslintParser);
 
 const eslintOutputSnapshotFolder = path.resolve(

diff --git a/packages/eslint-plugin/tests/rules/array-type.test.ts b/packages/eslint-plugin/tests/rules/array-type.test.ts
@@ -1924,7 +1924,7 @@ interface FooInterface {
 // -- eslint rule tester is not working with multi-pass
 // https://github.com/eslint/eslint/issues/11187
 describe('array-type (nested)', () => {
-  const linter = new TSESLint.Linter();
+  const linter = new TSESLint.Linter({ configType: 'eslintrc' });
   linter.defineRule('array-type', rule);
   linter.defineParser('@typescript-eslint/parser', parser);
 

diff --git a/packages/eslint-plugin/tests/rules/no-unused-vars/no-unused-vars-eslint.test.ts b/packages/eslint-plugin/tests/rules/no-unused-vars/no-unused-vars-eslint.test.ts
@@ -16,17 +16,25 @@ const ruleTester = new RuleTester({
   },
 });
 
-ruleTester.defineRule('use-every-a', context => {
-  /**
-   * Mark a variable as used
-   */
-  function useA(node: TSESTree.Node): void {
-    context.sourceCode.markVariableAsUsed('a', node);
-  }
-  return {
-    VariableDeclaration: useA,
-    ReturnStatement: useA,
-  };
+ruleTester.defineRule('use-every-a', {
+  create: context => {
+    /**
+     * Mark a variable as used
+     */
+    function useA(node: TSESTree.Node): void {
+      context.sourceCode.markVariableAsUsed('a', node);
+    }
+    return {
+      VariableDeclaration: useA,
+      ReturnStatement: useA,
+    };
+  },
+  defaultOptions: [],
+  meta: {
+    messages: {},
+    type: 'problem',
+    schema: [],
+  },
 });
 
 /**

diff --git a/packages/eslint-plugin/tests/rules/no-unused-vars/no-unused-vars.test.ts b/packages/eslint-plugin/tests/rules/no-unused-vars/no-unused-vars.test.ts
@@ -20,9 +20,17 @@ const withMetaParserOptions = {
 };
 
 // this is used to ensure that the caching the utility does does not impact the results done by no-unused-vars
-ruleTester.defineRule('collect-unused-vars', context => {
-  collectUnusedVariables(context);
-  return {};
+ruleTester.defineRule('collect-unused-vars', {
+  create(context) {
+    collectUnusedVariables(context);
+    return {};
+  },
+  defaultOptions: [],
+  meta: {
+    messages: {},
+    type: 'problem',
+    schema: [],
+  },
 });
 
 ruleTester.run('no-unused-vars', rule, {

diff --git a/packages/parser/package.json b/packages/parser/package.json
@@ -49,7 +49,7 @@
     "typecheck": "tsc -p tsconfig.json --noEmit"
   },
   "peerDependencies": {
-    "eslint": "^8.57.0"
+    "eslint": "^8.57.0 || ^9.0.0"
   },
   "dependencies": {
     "@typescript-eslint/scope-manager": "7.8.0",

diff --git a/packages/rule-tester/package.json b/packages/rule-tester/package.json
@@ -56,7 +56,7 @@
   },
   "peerDependencies": {
     "@eslint/eslintrc": ">=2",
-    "eslint": "^8.57.0"
+    "eslint": "^8.57.0 || ^9.0.0"
   },
   "devDependencies": {
     "@types/lodash.merge": "4.6.9",

diff --git a/packages/rule-tester/src/RuleTester.ts b/packages/rule-tester/src/RuleTester.ts
@@ -76,7 +76,7 @@ let defaultConfig = deepMerge(
 export class RuleTester extends TestFramework {
   readonly #testerConfig: TesterConfigWithDefaults;
   readonly #rules: Record<string, AnyRuleCreateFunction | AnyRuleModule> = {};
-  readonly #linter: Linter = new Linter();
+  readonly #linter: Linter = new Linter({ configType: 'eslintrc' });
 
   /**
    * Creates a new instance of RuleTester.

diff --git a/packages/type-utils/package.json b/packages/type-utils/package.json
@@ -60,9 +60,6 @@
     "rimraf": "*",
     "typescript": "*"
   },
-  "peerDependencies": {
-    "eslint": "^8.57.0"
-  },
   "peerDependenciesMeta": {
     "typescript": {
       "optional": true

diff --git a/packages/typescript-eslint/package.json b/packages/typescript-eslint/package.json
@@ -51,9 +51,6 @@
     "test": "jest --coverage --passWithNoTests",
     "typecheck": "tsc -p tsconfig.json --noEmit"
   },
-  "peerDependencies": {
-    "eslint": "^8.57.0"
-  },
   "dependencies": {
     "@typescript-eslint/eslint-plugin": "7.8.0",
     "@typescript-eslint/parser": "7.8.0",

diff --git a/packages/utils/package.json b/packages/utils/package.json
@@ -76,7 +76,7 @@
     "semver": "^7.6.0"
   },
   "peerDependencies": {
-    "eslint": "^8.57.0"
+    "eslint": "^8.57.0 || ^9.0.0"
   },
   "devDependencies": {
     "@typescript-eslint/parser": "7.8.0",

diff --git a/packages/utils/src/ts-eslint/Linter.ts b/packages/utils/src/ts-eslint/Linter.ts
@@ -276,7 +276,7 @@ namespace Linter {
     parserOptions?: ParserOptions;
   }
 
-  // TODO - RuleCreateFunction is no longer supported in ESLint v9
+  // TODO - remove RuleCreateFunction once we no longer support ESLint 8
   export type LegacyPluginRules = Record<
     string,
     AnyRuleCreateFunction | AnyRuleModule

diff --git a/packages/utils/src/ts-eslint/Rule.ts b/packages/utils/src/ts-eslint/Rule.ts
@@ -676,7 +676,7 @@ export type AnyRuleModuleWithMetaDocs = RuleModuleWithMetaDocs<
  * @see {@link LooseParserModule}, {@link LooseProcessorModule}
  */
 export type LooseRuleDefinition =
-  // TODO - ESLint v9 will remove support for RuleCreateFunction
+  // TODO - remove RuleCreateFunction once we no longer support ESLint 8
   | LooseRuleCreateFunction
   | {
       meta?: object | undefined;

diff --git a/packages/website-eslint/src/index.js b/packages/website-eslint/src/index.js
@@ -24,7 +24,7 @@ exports.astConverter = astConverter;
 exports.esquery = esquery;
 
 exports.createLinter = function () {
-  const linter = new Linter();
+  const linter = new Linter({ configType: 'eslintrc' });
   for (const name in plugin.rules) {
     linter.defineRule(`@typescript-eslint/${name}`, plugin.rules[name]);
   }

diff --git a/packages/website-eslint/types/eslint.d.ts b/packages/website-eslint/types/eslint.d.ts
@@ -9,7 +9,11 @@ it just uses `any` for the import - marking it as an untyped export. So adding t
 cannot use VSCode's cache ever - stubbing it out permanently.
 */
 declare module 'eslint' {
+  export interface LinterOptions {
+    configType?: 'eslintrc';
+  }
   export class Linter {
+    constructor(options: LinterOptions);
     defineRule(name: string, rule: unknown): void;
   }
 }