Migrate to ESLint 9 flat config format

eslint.config.js

@@ -0,0 +1,117 @@
+const eslint = require('@eslint/js')
+const tseslint = require('typescript-eslint')
+const jestPlugin = require('eslint-plugin-jest')
+const githubPlugin = require('eslint-plugin-github')
+const prettierPlugin = require('eslint-plugin-prettier')
+const { fixupPluginRules } = require('@eslint/compat')
+
+module.exports = tseslint.config(
+  // Ignore patterns
+  {
+    ignores: [
+      '**/node_modules/**',
+      '**/dist/**',
+      '**/coverage/**',
+      '**/*.json'
+    ]
+  },
+
+  // Base ESLint recommended rules
+  eslint.configs.recommended,
+
+  // TypeScript recommended configurations
+  ...tseslint.configs.recommended,
+
+  // TypeScript files configuration
+  {
+    files: ['**/*.ts'],
+    languageOptions: {
+      parserOptions: {
+        projectService: true,
+        tsconfigRootDir: __dirname
+      },
+      globals: {
+        ...jestPlugin.environments.globals.globals
+      }
+    },
+    plugins: {
+      jest: jestPlugin,
+      github: fixupPluginRules(githubPlugin),
+      prettier: prettierPlugin
+    },
+    rules: {
+      // ESLint core rules
+      'camelcase': 'off',
+      'no-console': 'off',
+      'no-unused-vars': 'off',
+      'semi': ['error', 'never'],
+      'func-call-spacing': ['error', 'never'],
+
+      // Prettier integration
+      'prettier/prettier': 'error',
+
+      // TypeScript custom rules
+      '@typescript-eslint/array-type': 'error',
+      '@typescript-eslint/await-thenable': 'error',
+      '@typescript-eslint/ban-ts-comment': 'error',
+      '@typescript-eslint/consistent-type-assertions': 'error',
+      '@typescript-eslint/explicit-member-accessibility': [
+        'error',
+        { accessibility: 'no-public' }
+      ],
+      '@typescript-eslint/explicit-function-return-type': [
+        'error',
+        { allowExpressions: true }
+      ],
+      '@typescript-eslint/no-array-constructor': 'error',
+      '@typescript-eslint/no-empty-interface': 'error',
+      '@typescript-eslint/no-explicit-any': 'error',
+      '@typescript-eslint/no-extraneous-class': 'error',
+      '@typescript-eslint/no-for-in-array': 'error',
+      '@typescript-eslint/no-inferrable-types': 'error',
+      '@typescript-eslint/no-misused-new': 'error',
+      '@typescript-eslint/no-namespace': 'error',
+      '@typescript-eslint/no-non-null-assertion': 'warn',
+      '@typescript-eslint/no-require-imports': 'error',
+      '@typescript-eslint/no-unnecessary-qualifier': 'error',
+      '@typescript-eslint/no-unnecessary-type-assertion': 'error',
+      '@typescript-eslint/no-unused-vars': 'error',
+      '@typescript-eslint/no-useless-constructor': 'error',
+      '@typescript-eslint/no-var-requires': 'error',
+      '@typescript-eslint/prefer-for-of': 'warn',
+      '@typescript-eslint/prefer-function-type': 'warn',
+      '@typescript-eslint/prefer-includes': 'error',
+      '@typescript-eslint/prefer-string-starts-ends-with': 'error',
+      '@typescript-eslint/promise-function-async': 'error',
+      '@typescript-eslint/require-array-sort-compare': 'error',
+      '@typescript-eslint/restrict-plus-operands': 'error',
+      '@typescript-eslint/space-before-function-paren': 'off',
+      '@typescript-eslint/unbound-method': 'error',
+
+      // GitHub plugin rules
+      'eslint-comments/no-use': 'off',
+      'eslint-comments/no-unused-disable': 'off',
+      'i18n-text/no-en': 'off',
+      'import/no-namespace': 'off',
+
+      // Jest plugin rules
+      'jest/no-disabled-tests': 'warn',
+      'jest/no-focused-tests': 'error',
+      'jest/no-identical-title': 'error',
+      'jest/prefer-to-have-length': 'warn',
+      'jest/valid-expect': 'error'
+    }
+  },
+
+  // JavaScript files configuration
+  {
+    files: ['**/*.js'],
+    ...tseslint.configs.disableTypeChecked,
+    rules: {
+      // Disable TypeScript-specific rules for JavaScript files
+      '@typescript-eslint/explicit-function-return-type': 'off',
+      '@typescript-eslint/no-explicit-any': 'off',
+      '@typescript-eslint/explicit-member-accessibility': 'off'
+    }
+  }
+)

package.json

@@ -28,7 +28,7 @@
     "bundle": "npm run format:write && npm run package",
     "format:write": "prettier --write .",
     "format:check": "prettier --check .",
-    "lint": "eslint . -c ./.github/linters/.eslintrc.yml",
+    "lint": "eslint .",
     "package": "ncc build --minify src/index.ts -o dist --license licenses.txt",
     "test": "jest",
     "all": "npm run format:write && npm run lint && npm run test && npm run package",
@@ -41,6 +41,8 @@
     "@linearb/gitstream-core": "2.1.215"
   },
   "devDependencies": {
+    "@eslint/compat": "^1.2.3",
+    "@eslint/js": "^9.39.1",
     "@jest/globals": "^30.2.0",
     "@types/jest": "^30.0.0",
     "@types/node": "^24.10.0",
@@ -56,7 +58,8 @@
     "prettier": "^3.6.2",
     "prettier-eslint": "^16.4.2",
     "ts-jest": "^29.4.5",
-    "typescript": "^5.9.3"
+    "typescript": "^5.9.3",
+    "typescript-eslint": "^8.46.3"
   },
   "jest": {
     "preset": "ts-jest",