non-breaking approach

README.md

@@ -43,21 +43,29 @@ module.exports = {
 ```
 
 To correctly parse gjs/gts:
-Do not set an override for the parser in the global config.
-To use e.g. the typescript parser, the following should be used
 
 ```js
 // .eslintrc.js
 module.exports = {
   plugins: ['ember'],
-  // parser: '@typescript-eslint/parser', <-- needs to be removed, or set the gts/gjs one
-  // so we could also have:
-  // parser: "eslint-plugin-ember/gts-parser",
   extends: [
     'eslint:recommended',
-    'plugin:@typescript-eslint/base', // or typescript-eslint/recommended, must come before plugin:ember/recommended
     'plugin:ember/recommended', // or other configuration
   ],
+  overrides: [
+    {
+      files: ['**/*.gts'],
+      extends: [
+        'plugin:ember/recommended-gjs',
+      ]
+    },
+    {
+      files: ['**/*.gjs'],
+      extends: [
+        'plugin:ember/recommended-gjs',
+      ]
+    }
+  ],
   rules: {
     // override / enable optional rules
     'ember/no-replace-test-comments': 'error'

lib/config/recommended-gjs.js

@@ -0,0 +1,41 @@
+const rules = require('../recommended-rules');
+
+module.exports = {
+  root: true,
+
+  parserOptions: {
+    ecmaVersion: 2020,
+    sourceType: 'module',
+  },
+
+  env: {
+    browser: true,
+    es2020: true,
+  },
+
+  plugins: ['ember'],
+
+  rules,
+
+  overrides: [
+    /**
+     * We don't want to *always* have the preprocessor active,
+     * it's only relevant on gjs and gts files.
+     *
+     * Additionally, we need to declare a global (which is private API)
+     * so that ESLint doesn't report errors about the variable being undefined.
+     * While this is true, it's a temporary thing for babel to do further processing
+     * on -- and isn't relevant to user-land code.
+     */
+    {
+      files: ['**/*.gts'],
+      parser: 'eslint-plugin-ember/gts-parser',
+      processor: 'ember/<noop>',
+    },
+    {
+      files: ['**/*.gjs'],
+      parser: 'eslint-plugin-ember/gjs-parser',
+      processor: 'ember/<noop>',
+    },
+  ],
+};

lib/config/recommended.js

@@ -1,4 +1,5 @@
 const rules = require('../recommended-rules');
+const util = require('ember-template-imports/src/util');
 
 module.exports = {
   root: true,
@@ -28,12 +29,11 @@ module.exports = {
      * on -- and isn't relevant to user-land code.
      */
     {
-      files: ['**/*.gts'],
-      parser: require.resolve('../parsers/gts-parser'),
-    },
-    {
-      files: ['**/*.gjs'],
-      parser: require.resolve('../parsers/gjs-parser'),
+      files: ['**/*.gjs', '**/*.gts'],
+      processor: 'ember/<template>',
+      globals: {
+        [util.TEMPLATE_TAG_PLACEHOLDER]: 'readonly',
+      },
     },
   ],
 };

lib/index.js

@@ -2,10 +2,18 @@
 
 const requireIndex = require('requireindex');
 
+const gjs = require('./preprocessors/glimmer');
+const noop = require('./preprocessors/noop');
+
 module.exports = {
   rules: requireIndex(`${__dirname}/rules`),
   configs: requireIndex(`${__dirname}/config`),
   utils: {
     ember: require('./utils/ember'),
   },
+  processors: {
+    // https://eslint.org/docs/developer-guide/working-with-plugins#file-extension-named-processor
+    '<template>': gjs,
+    '<noop>': noop,
+  },
 };