chore(lint): add eslint and prettier with ionic configs and CI workflow

.github/CONTRIBUTING.md

@@ -53,6 +53,8 @@ Talk to us before creating a PR that refactors the code or directory structure o
 
 Make sure to follow the existing code style as much as possible.
 
+Code is linted with ESLint and formatted with Prettier, and pull requests must pass `npm run lint`. Run `npm run lint:fix` to fix what can be fixed automatically.
+
 * No underscores prefixing JS functions.
 * Use flat Sass:
   * **Don't** use [BEM conventions](https://css-tricks.com/bem-101/)

.github/workflows/CI.yml

@@ -7,6 +7,23 @@ name: Install Dependencies, Lint, Build and Test
 on: [pull_request]
 
 jobs:
+  lint:
+    name: Lint
+    # Lint once on Linux. Windows runners check out with CRLF line endings,
+    # which Prettier would report as formatting changes.
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+    - name: Use Node.js 24
+      uses: actions/setup-node@949feb2413d6458794dcd2491c4babbbce0c15c1 # v7.1.0
+      with:
+        node-version: 24
+    - name: Install Dependencies
+      run: npm ci
+    - name: Lint
+      run: npm run lint
+
   test:
     name: Test on node ${{ matrix.node_version }} and ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
@@ -21,15 +38,13 @@ jobs:
         os: [windows-latest, macOS-latest]
 
     steps:
-    - uses: actions/checkout@v7
+    - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
     - name: Use Node.js ${{ matrix.node_version }}
-      uses: actions/setup-node@v7
+      uses: actions/setup-node@949feb2413d6458794dcd2491c4babbbce0c15c1 # v7.1.0
       with:
         node-version: ${{ matrix.node_version }}
     - name: Install Dependencies
       run: npm ci
-    - name: Lint
-      run: npm run lint
     - name: Build
       run: npm run build -- --configuration=production
     - name: Test

.gitignore

@@ -11,7 +11,8 @@ www/
 log.txt
 *.sublime-project
 *.sublime-workspace
-.vscode/
+.vscode/*
+!.vscode/extensions.json
 npm-debug.log*
 .firebase/
 .idea/

.prettierignore

@@ -0,0 +1,5 @@
+# Prettier only reads the root .gitignore, not the ones inside the native
+# projects, so ignore them here to skip Capacitor's copied web build and
+# Gradle's build output.
+android/
+ios/

.vscode/extensions.json

@@ -0,0 +1,8 @@
+{
+  "recommendations": [
+    "dbaeumer.vscode-eslint",
+    "esbenp.prettier-vscode",
+    "Angular.ng-template",
+    "Webnative.webnative"
+  ]
+}

eslint.config.js

@@ -1,38 +1,29 @@
 // @ts-check
-const eslint = require('@eslint/js');
-const tseslint = require('typescript-eslint');
+const ionic = require('@ionic/eslint-config/recommended');
 const angular = require('angular-eslint');
+const { defineConfig } = require('eslint/config');
 
-module.exports = tseslint.config(
+module.exports = defineConfig([
   {
-    ignores: ['www/**', 'dist/**', 'coverage/**', '.angular/**'],
+    ignores: ['www/**', 'dist/**', 'coverage/**', '.angular/**', 'android/**', 'ios/**'],
   },
+  ionic,
   {
     files: ['**/*.ts'],
-    extends: [
-      eslint.configs.recommended,
-      ...tseslint.configs.recommended,
-      ...angular.configs.tsRecommended,
-    ],
+    extends: [angular.configs.tsRecommended],
     processor: angular.processInlineTemplates,
     rules: {
+      // Ionic's base level; `recommended` makes it an error, which is meant for libraries.
+      '@typescript-eslint/explicit-module-boundary-types': 'warn',
       '@typescript-eslint/explicit-member-accessibility': 'off',
       '@typescript-eslint/explicit-function-return-type': 'off',
-      '@typescript-eslint/no-inferrable-types': [
-        'error',
-        { ignoreParameters: true },
-      ],
+      '@typescript-eslint/no-inferrable-types': ['error', { ignoreParameters: true }],
       '@typescript-eslint/no-non-null-assertion': 'error',
       '@typescript-eslint/no-explicit-any': 'off',
       '@typescript-eslint/member-ordering': [
         'error',
         {
-          default: [
-            'static-field',
-            'instance-field',
-            'static-method',
-            'instance-method',
-          ],
+          default: ['static-field', 'instance-field', 'static-method', 'instance-method'],
         },
       ],
       '@typescript-eslint/naming-convention': [
@@ -47,23 +38,16 @@ module.exports = tseslint.config(
       '@angular-eslint/no-output-rename': 'error',
       '@angular-eslint/use-lifecycle-interface': 'error',
       '@angular-eslint/use-pipe-transform-interface': 'error',
-      quotes: ['error', 'single'],
-      semi: ['error', 'always'],
-      'max-len': ['error', { code: 140 }],
       'no-console': 'off',
       curly: 'error',
       eqeqeq: 'error',
       'no-empty': 'off',
-      'arrow-parens': ['error', 'as-needed'],
       'object-shorthand': 'error',
-      'eol-last': 'error',
-      'no-multiple-empty-lines': ['error', { max: 1 }],
-      'no-trailing-spaces': 'error',
     },
   },
   {
     files: ['**/*.html'],
-    extends: [...angular.configs.templateRecommended],
+    extends: [angular.configs.templateRecommended],
     rules: {},
-  }
-);
+  },
+]);