FEC-739: fix(templates): migrate to ESLint 9 flat config format (#3954)

* fix(templates): migrate to ESLint 9 flat config format

Replace legacy .eslintrc.js with eslint.config.js across all 4 starter
templates. Upgrade eslint to ^9.0.0 and remove @types/eslint <9 resolution.

Fixes FEC-739

* chore(templates): remove unnecessary jest-runner-eslint pnpm override

jest-runner-eslint@2.3.0 works with ESLint 9 without an explicit override,
as confirmed by the monorepo root running the same setup successfully.

* chore: update lockfile for eslint ^9.0.0 in templates

Author: misama-ct

application-templates/starter-typescript/.eslintrc.js

@@ -0,0 +1,30 @@
+process.env.ENABLE_NEW_JSX_TRANSFORM = 'true';
+
+const graphqlPlugin = require('@graphql-eslint/eslint-plugin');
+const mcAppConfig = require('@commercetools-frontend/eslint-config-mc-app');
+
+module.exports = [
+  ...mcAppConfig,
+  {
+    files: ['**/*.ctp.graphql'],
+    plugins: { '@graphql-eslint': graphqlPlugin },
+    languageOptions: {
+      parser: graphqlPlugin,
+      parserOptions: {
+        graphQLConfig: {
+          schema: './schemas/ctp.json',
+        },
+      },
+    },
+    rules: {
+      '@graphql-eslint/known-type-names': 'error',
+      '@graphql-eslint/known-argument-names': 'error',
+      '@graphql-eslint/known-directives': 'error',
+      '@graphql-eslint/scalar-leafs': 'error',
+    },
+  },
+  {
+    files: ['eslint.config.js'],
+    rules: { 'import/extensions': 'off' },
+  },
+];

application-templates/starter-typescript/eslint.config.js

@@ -69,7 +69,7 @@
     "@types/react-router": "^5.1.20",
     "@types/react-router-dom": "^5.3.3",
     "@types/testing-library__jest-dom": "^5.14.9",
-    "eslint": "8.57.1",
+    "eslint": "^9.0.0",
     "eslint-formatter-pretty": "4.1.0",
     "formik": "2.4.6",
     "graphql": "^16.8.0",
@@ -95,7 +95,6 @@
   "resolutions": {
     "@emotion/react": "^11.14.0",
     "@emotion/styled": "^11.14.0",
-    "@types/eslint": "<9",
     "@types/react-router": "<6",
     "@types/react-router-dom": "<6",
     "headers-polyfill": "3.2.5",

application-templates/starter-typescript/package.json

@@ -0,0 +1,18 @@
+process.env.ENABLE_NEW_JSX_TRANSFORM = 'true';
+
+const mcAppConfig = require('@commercetools-frontend/eslint-config-mc-app');
+
+module.exports = [
+  ...mcAppConfig,
+  {
+    files: ['**/*.{js,jsx,tsx}'],
+    rules: {
+      'react/jsx-uses-react': 'off',
+      'react/react-in-jsx-scope': 'off',
+    },
+  },
+  {
+    files: ['eslint.config.js'],
+    rules: { 'import/extensions': 'off' },
+  },
+];

application-templates/starter/.eslintrc.js

@@ -67,7 +67,7 @@
     "@types/react-router": "^5.1.20",
     "@types/react-router-dom": "^5.3.3",
     "@types/testing-library__jest-dom": "^5.14.9",
-    "eslint": "8.57.1",
+    "eslint": "^9.0.0",
     "eslint-formatter-pretty": "4.1.0",
     "formik": "2.4.6",
     "graphql": "^16.8.0",
@@ -93,7 +93,6 @@
   "resolutions": {
     "@emotion/react": "^11.14.0",
     "@emotion/styled": "^11.14.0",
-    "@types/eslint": "<9",
     "@types/react-router": "<6",
     "@types/react-router-dom": "<6",
     "headers-polyfill": "3.2.5",

application-templates/starter/eslint.config.js

@@ -0,0 +1,30 @@
+process.env.ENABLE_NEW_JSX_TRANSFORM = 'true';
+
+const graphqlPlugin = require('@graphql-eslint/eslint-plugin');
+const mcAppConfig = require('@commercetools-frontend/eslint-config-mc-app');
+
+module.exports = [
+  ...mcAppConfig,
+  {
+    files: ['**/*.ctp.graphql'],
+    plugins: { '@graphql-eslint': graphqlPlugin },
+    languageOptions: {
+      parser: graphqlPlugin,
+      parserOptions: {
+        graphQLConfig: {
+          schema: './schemas/ctp.json',
+        },
+      },
+    },
+    rules: {
+      '@graphql-eslint/known-type-names': 'error',
+      '@graphql-eslint/known-argument-names': 'error',
+      '@graphql-eslint/known-directives': 'error',
+      '@graphql-eslint/scalar-leafs': 'error',
+    },
+  },
+  {
+    files: ['eslint.config.js'],
+    rules: { 'import/extensions': 'off' },
+  },
+];

application-templates/starter/package.json

@@ -69,7 +69,7 @@
     "@types/react-router": "^5.1.20",
     "@types/react-router-dom": "^5.3.3",
     "@types/testing-library__jest-dom": "^5.14.9",
-    "eslint": "8.57.1",
+    "eslint": "^9.0.0",
     "eslint-formatter-pretty": "4.1.0",
     "formik": "2.4.6",
     "graphql": "^16.8.0",
@@ -95,7 +95,6 @@
   "resolutions": {
     "@emotion/react": "^11.14.0",
     "@emotion/styled": "^11.14.0",
-    "@types/eslint": "<9",
     "@types/react-router": "<6",
     "@types/react-router-dom": "<6",
     "headers-polyfill": "3.2.5",