Try fully linting gjs and gts (eslint + template-lint + prettier)

frontend/.eslintrc.js

@@ -1,17 +1,203 @@
 'use strict';
 
-const { configs } = require('@nullvoxpopuli/eslint-configs');
-const { baseConfig: baseNode } = require('@nullvoxpopuli/eslint-configs/configs/node');
+function hasDep(depName) {
+  try {
+    return Boolean(require.resolve(depName));
+  } catch (e) {
+    if (e.message.startsWith(`Cannot find module '${depName}'`)) return false;
 
-const config = configs.ember();
+    throw e;
+  }
+}
+
+function proposedEmberDefault(personalPreferences) {
+  let hasTypeScript = hasDep('typescript');
+  let noPrettier = process.env.NO_PRETTIER;
+
+  const configBuilder = {
+    modules: {
+      browser: {
+        get js() {
+          return {
+            files: [
+              '{src,app,addon,addon-test-support,tests}/**/*.{gjs,js}',
+              'tests/dummy/config/deprecation-workflow.js',
+              'config/deprecation-workflow.js',
+            ],
+            parser: 'babel-eslint',
+            parserOptions: {
+              ecmaVersion: 2022,
+              sourceType: 'module',
+              ecmaFeatures: {
+                legacyDecorators: true,
+              },
+            },
+            plugins: ['ember'],
+            extends: [
+              'eslint:recommended',
+              'plugin:ember/recommended',
+              ...(noPrettier ? [] : ['plugin:prettier/recommended']),
+            ],
+            env: {
+              browser: true,
+            },
+            rules: {
+              ...personalPreferences.rules,
+            },
+          }
+        },
+        get ts() {
+          if (!hasTypeScript) return;
+
+          return {
+            files: ['{src,app,addon,addon-test-support,tests,types}/**/*.{gts,ts}'],
+            parser: '@typescript-eslint/parser',
+            plugins: ['ember'],
+            extends: [
+              'eslint:recommended',
+              'plugin:ember/recommended',
+              ...(noPrettier ? [] : ['plugin:prettier/recommended']),
+              'plugin:@typescript-eslint/recommended',
+            ],
+            env: {
+              browser: true,
+            },
+            rules: {
+              // type imports are removed in builds
+              '@typescript-eslint/consistent-type-imports': 'error',
+
+              // prefer inference, but it is recommended to declare
+              // return types around public API
+              '@typescript-eslint/explicit-function-return-type': 'off',
+              '@typescript-eslint/explicit-module-boundary-types': 'off',
+
+              // Allows placeholder args to still be defined for
+              // documentation or "for later" purposes
+              '@typescript-eslint/no-unused-vars': ['error', { argsIgnorePattern: '^_' }],
+              ...personalPreferences.rules,
+            },
+          }
+        },
+        get declarations() {
+          if (!hasTypeScript) return;
+
+          return {
+            files: ['**/*.d.ts'],
+            extends: [
+              'eslint:recommended',
+              ...(noPrettier ? [] : ['plugin:prettier/recommended']),
+              'plugin:@typescript-eslint/recommended',
+            ],
+            env: {
+              browser: true,
+            },
+            rules: {
+              '@typescript-eslint/no-empty-interface': 'off'
+            }
+          }
+        }
+      },
+      tests: {
+        get js() {
+          let browserJS = configBuilder.modules.browser.js;
+          return {
+            ...browserJS,
+            files: ['tests/**/*-test.{gjs,js}'],
+            extends: [...browserJS.extends, 'plugin:qunit/recommended'],
+          }
+        },
+        get ts() {
+          if (!hasTypeScript) return;
+
+          let browserTS = configBuilder.modules.browser.ts;
+
+          return {
+            ...browserTS,
+            files: ['tests/**/*-test.{gts,ts}'],
+            extends: [...browserTS.extends, 'plugin:qunit/recommended'],
+          }
+        },
+      }
+    },
+    commonjs: {
+      node: {
+        get js() {
+          return {
+            files: [
+              './*.{cjs,js}',
+              './config/**/*.js',
+              './lib/*/index.js',
+              './server/**/*.js',
+              './blueprints/*/index.js',
+            ],
+            parserOptions: {
+              sourceType: 'script',
+            },
+            env: {
+              browser: false,
+              node: true,
+            },
+            plugins: ['node'],
+            extends: ['plugin:node/recommended'],
+            rules: {
+              ...personalPreferences.rules,
+              // this can be removed once the following is fixed
+              // https://github.com/mysticatea/eslint-plugin-node/issues/77
+              'node/no-unpublished-require': 'off',
+            },
+          }
+        }
+      }
+    }
+  }
+
+  return configBuilder;
+}
+
+
+const personalPreferences = {
+  rules: {
+    // const has misleading safety implications
+    // look in to "liberal let"
+    'prefer-const': 'off',
+
+    // people should know that no return is undefined in JS
+    'getter-return': ['error', { allowImplicit: true }],
+
+    'padding-line-between-statements': [
+      'error',
+      { blankLine: 'always', prev: '*', next: 'return' },
+      { blankLine: 'always', prev: '*', next: 'break' },
+      { blankLine: 'always', prev: '*', next: 'block-like' },
+      { blankLine: 'always', prev: 'block-like', next: '*' },
+      { blankLine: 'always', prev: ['const', 'let'], next: '*' },
+      { blankLine: 'always', prev: '*', next: ['const', 'let'] },
+      { blankLine: 'any', prev: ['const', 'let'], next: ['const', 'let'] },
+      { blankLine: 'any', prev: ['*'], next: ['case'] },
+    ],
+  },
+}
+
+const config = proposedEmberDefault(personalPreferences);
 
 module.exports = {
-  ...config,
+  root: true,
+  /**
+   * No root rules needed, because we define everything with overrides
+   * so that understanding what set of rules is applied to what files
+   * is easier to understand.
+   *
+   * This can be debugged with
+   *
+   * eslint --print-config ./path/to/file
+   */
+  rules: {},
   overrides: [
-    ...config.overrides,
-    {
-      ...baseNode,
-      files: ['browserstack.testem.js'],
-    },
-  ],
+    config.commonjs.node.js,
+    config.modules.browser.js,
+    config.modules.browser.ts,
+    config.modules.browser.declarations,
+    config.modules.tests.js,
+    config.modules.tests.ts,
+  ].filter(Boolean),
 };

frontend/.prettierrc.js

@@ -0,0 +1,17 @@
+'use strict';
+
+module.exports = {
+  // Personal preference
+  printWidth: 100,
+
+  // Default Ember (proposed)
+  plugins: ['prettier-plugin-ember-template-tag'],
+  overrides: [
+    {
+      files: '*.{js,ts,gjs,gts}',
+      options: {
+        singleQuote: true,
+      },
+    },
+  ],
+};

frontend/package.json

@@ -109,7 +109,7 @@
     "ember-resolver": "^8.0.3",
     "ember-source": "^4.7.0",
     "ember-template-imports": "^3.3.1",
-    "ember-template-lint": "~4.4.0",
+    "ember-template-lint": "^5.0.0-alpha.0",
     "ember-template-lint-plugin-prettier": "^4.0.0",
     "esbuild-loader": "^2.19.0",
     "eslint": "^7.32.0",
@@ -118,7 +118,8 @@
     "fractal-page-object": "^0.3.0",
     "loader.js": "^4.7.0",
     "onp": "^2.0.3",
-    "prettier": "^2.3.2",
+    "prettier": "^2.7.1",
+    "prettier-plugin-ember-template-tag": "^0.0.3",
     "qunit": "^2.19.1",
     "qunit-dom": "^2.0.0",
     "rollup": "^2.77.2",
@@ -162,6 +163,7 @@
     "ember-repl": "^2.0.63",
     "ember-resources": "^5.6.0",
     "ember-statechart-component": "6.1.2",
+    "eslint-plugin-ember": "^11.2.0",
     "highlight.js": "^11.6.0",
     "highlightjs-glimmer": "^2.0.1",
     "html-to-image": "^1.9.0",

frontend/tests/unit/services/editor-test.js

@@ -7,6 +7,7 @@ module('Unit | Service | editor', function (hooks) {
   // TODO: Replace this with your real tests.
   test('it exists', function (assert) {
     let service = this.owner.lookup('service:editor');
+
     assert.ok(service);
   });
 });

frontend/types/limber/index.d.ts

@@ -1,4 +1,4 @@
-import Ember from 'ember';
+import type Ember from 'ember';
 
 declare global {
   interface Array<T> extends Ember.ArrayPrototypeExtensions<T> {}