ember-cli 6.1, eslint 9, eslint flat config, RFC#1055 (#320)

* ember-cli < 6.1 is too old

* Switch to ESLint 9

* fix

* afix

* fix

* ope

* Cleanup, update prettier config

* ope

* Fix lints

* Lints

* lints

* Fix assertions

* Use TypeScript 5.6

* Upgrade typescript-eslint

* Set project: true

* Override ember-cli's tsconfig.json see: ember-cli/ember-cli#10611 and ember-cli/ember-cli#10613 and ember-cli/ember-cli#10612

* Re-lock

.gitignore

@@ -17,3 +17,5 @@ node_modules/
 
 # Test artifacts
 coverage/
+tests/my-addon/
+tests/test-app/

files/__addonLocation__/_js_eslint.config.mjs

@@ -0,0 +1,114 @@
+/**
+ * Debugging:
+ *   https://eslint.org/docs/latest/use/configure/debug
+ *  ----------------------------------------------------
+ *
+ *   Print a file's calculated configuration
+ *
+ *     npx eslint --print-config path/to/file.js
+ *
+ *   Inspecting the config
+ *
+ *     npx eslint --inspect-config
+ *
+ */
+import babelParser from '@babel/eslint-parser';
+import js from '@eslint/js';
+import prettier from 'eslint-config-prettier';
+import ember from 'eslint-plugin-ember/recommended';
+import importPlugin from 'eslint-plugin-import';
+import n from 'eslint-plugin-n';
+import globals from 'globals';
+
+const esmParserOptions = {
+  ecmaFeatures: { modules: true },
+  ecmaVersion: 'latest',
+};
+
+export default [
+  js.configs.recommended,
+  prettier,
+  ember.configs.base,
+  ember.configs.gjs,
+  /**
+   * Ignores must be in their own object
+   * https://eslint.org/docs/latest/use/configure/ignore
+   */
+  {
+    ignores: ['dist/', 'declarations/', 'node_modules/', 'coverage/', '!**/.*'],
+  },
+  /**
+   * https://eslint.org/docs/latest/use/configure/configuration-files#configuring-linter-options
+   */
+  {
+    linterOptions: {
+      reportUnusedDisableDirectives: 'error',
+    },
+  },
+  {
+    files: ['**/*.js'],
+    languageOptions: {
+      parser: babelParser,
+    },
+  },
+  {
+    files: ['**/*.{js,gjs}'],
+    languageOptions: {
+      parserOptions: esmParserOptions,
+      globals: {
+        ...globals.browser,
+      },
+    },
+  },
+  {
+    files: ['src/**/*'],
+    plugins: {
+      import: importPlugin,
+    },
+    rules: {
+      // require relative imports use full extensions
+      'import/extensions': ['error', 'always', { ignorePackages: true }],
+    },
+  },
+  /**
+   * CJS node files
+   */
+  {
+    files: [
+      '**/*.cjs',
+      '.prettierrc.js',
+      '.stylelintrc.js',
+      '.template-lintrc.js',
+      'addon-main.cjs',
+    ],
+    plugins: {
+      n,
+    },
+
+    languageOptions: {
+      sourceType: 'script',
+      ecmaVersion: 'latest',
+      globals: {
+        ...globals.node,
+      },
+    },
+  },
+  /**
+   * ESM node files
+   */
+  {
+    files: ['**/*.mjs'],
+    plugins: {
+      n,
+    },
+
+    languageOptions: {
+      sourceType: 'module',
+      ecmaVersion: 'latest',
+      parserOptions: esmParserOptions,
+      globals: {
+        ...globals.node,
+      },
+    },
+  },
+];

files/__addonLocation__/_ts_eslint.config.mjs

@@ -0,0 +1,133 @@
+/**
+ * Debugging:
+ *   https://eslint.org/docs/latest/use/configure/debug
+ *  ----------------------------------------------------
+ *
+ *   Print a file's calculated configuration
+ *
+ *     npx eslint --print-config path/to/file.js
+ *
+ *   Inspecting the config
+ *
+ *     npx eslint --inspect-config
+ *
+ */
+import babelParser from '@babel/eslint-parser';
+import js from '@eslint/js';
+import prettier from 'eslint-config-prettier';
+import ember from 'eslint-plugin-ember/recommended';
+import importPlugin from 'eslint-plugin-import';
+import n from 'eslint-plugin-n';
+import globals from 'globals';
+import ts from 'typescript-eslint';
+
+const parserOptions = {
+  esm: {
+    js: {
+      ecmaFeatures: { modules: true },
+      ecmaVersion: 'latest',
+    },
+    ts: {
+      projectService: true,
+      project: true,
+      tsconfigRootDir: import.meta.dirname,
+    },
+  },
+};
+
+export default ts.config(
+  js.configs.recommended,
+  ember.configs.base,
+  ember.configs.gjs,
+  ember.configs.gts,
+  prettier,
+  /**
+   * Ignores must be in their own object
+   * https://eslint.org/docs/latest/use/configure/ignore
+   */
+  {
+    ignores: ['dist/', 'declarations/', 'node_modules/', 'coverage/', '!**/.*'],
+  },
+  /**
+   * https://eslint.org/docs/latest/use/configure/configuration-files#configuring-linter-options
+   */
+  {
+    linterOptions: {
+      reportUnusedDisableDirectives: 'error',
+    },
+  },
+  {
+    files: ['**/*.js'],
+    languageOptions: {
+      parser: babelParser,
+    },
+  },
+  {
+    files: ['**/*.{js,gjs}'],
+    languageOptions: {
+      parserOptions: parserOptions.esm.js,
+      globals: {
+        ...globals.browser,
+      },
+    },
+  },
+  {
+    files: ['**/*.{ts,gts}'],
+    languageOptions: {
+      parser: ember.parser,
+      parserOptions: parserOptions.esm.ts,
+    },
+    extends: [...ts.configs.recommendedTypeChecked, ember.configs.gts],
+  },
+  {
+    files: ['src/**/*'],
+    plugins: {
+      import: importPlugin,
+    },
+    rules: {
+      // require relative imports use full extensions
+      'import/extensions': ['error', 'always', { ignorePackages: true }],
+    },
+  },
+  /**
+   * CJS node files
+   */
+  {
+    files: [
+      '**/*.cjs',
+      '.prettierrc.js',
+      '.stylelintrc.js',
+      '.template-lintrc.js',
+      'addon-main.cjs',
+    ],
+    plugins: {
+      n,
+    },
+
+    languageOptions: {
+      sourceType: 'script',
+      ecmaVersion: 'latest',
+      globals: {
+        ...globals.node,
+      },
+    },
+  },
+  /**
+   * ESM node files
+   */
+  {
+    files: ['**/*.mjs'],
+    plugins: {
+      n,
+    },
+
+    languageOptions: {
+      sourceType: 'module',
+      ecmaVersion: 'latest',
+      parserOptions: parserOptions.esm.js,
+      globals: {
+        ...globals.node,
+      },
+    },
+  },
+);