Migrate eslint to v9

.eslintignore

@@ -1,3 +0,0 @@
-node_modules/
-lib/
-dist/

.eslintrc.json

@@ -1,15 +0,0 @@
-{
-    "env": { "node": true, "jest": true },
-    "parser": "@typescript-eslint/parser",
-    "parserOptions": { "ecmaVersion": 9, "sourceType": "module" },
-    "extends": [
-      "eslint:recommended",
-      "plugin:@typescript-eslint/eslint-recommended",
-      "plugin:@typescript-eslint/recommended",
-      "plugin:import/errors",
-      "plugin:import/warnings",
-      "plugin:import/typescript",
-      "plugin:prettier/recommended"
-    ],
-    "plugins": ["@typescript-eslint"]
-}

eslint.config.mjs

@@ -0,0 +1,58 @@
+import github from 'eslint-plugin-github'
+import jest from 'eslint-plugin-jest'
+import prettier from 'eslint-plugin-prettier/recommended'
+
+const githubConfigs = github.getFlatConfigs()
+
+export default [
+  {
+    ignores: ['**/node_modules/**', '**/lib/**', '**/dist/**']
+  },
+  githubConfigs.recommended,
+  ...githubConfigs.typescript,
+  prettier,
+  {
+    files: ['**/*.ts'],
+    languageOptions: {
+      parserOptions: {
+        project: './tsconfig.eslint.json'
+      }
+    },
+    rules: {
+      // Prettier
+      'prettier/prettier': ['error', {endOfLine: 'auto'}],
+
+      // Disable rules that conflict with project style
+      'eslint-comments/no-use': 'off',
+      'github/no-then': 'off',
+      'github/filenames-match-regex': 'off',
+      'github/array-foreach': 'off',
+      'import/no-namespace': 'off',
+      'import/no-commonjs': 'off',
+      'import/named': 'off',
+      'import/no-unresolved': 'off',
+      'i18n-text/no-en': 'off',
+      'filenames/match-regex': 'off',
+      'no-shadow': 'off',
+      'no-unused-vars': 'off',
+      'no-undef': 'off',
+      camelcase: 'off',
+
+      // TypeScript rules
+      '@typescript-eslint/no-unused-vars': 'off',
+      '@typescript-eslint/no-explicit-any': 'off',
+      '@typescript-eslint/no-shadow': 'off',
+      '@typescript-eslint/array-type': 'off',
+      '@typescript-eslint/no-require-imports': 'off'
+    }
+  },
+  {
+    files: ['**/__tests__/**/*.ts'],
+    ...jest.configs['flat/recommended'],
+    rules: {
+      ...jest.configs['flat/recommended'].rules,
+      'jest/expect-expect': 'off',
+      'jest/no-conditional-expect': 'off'
+    }
+  }
+]

tsconfig.eslint.json

@@ -0,0 +1,8 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "."
+  },
+  "include": ["src/**/*.ts", "__tests__/**/*.ts", "*.ts"],
+  "exclude": ["node_modules", "lib", "dist"]
+}