build: add eslint and web-ext to dev packages

.github/workflows/build.yml

@@ -21,13 +21,13 @@ jobs:
 
       - name: Setup Node.js
         uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e  # v6.4.0
-      - name: Install web-ext
-        run: npm install --global web-ext
+      - name: Install the dependencies
+        run: npm ci
       - name: Display web-ext version
-        run: web-ext --version
+        run: npx web-ext --version
 
       - name: Build with web-ext
-        run: web-ext build
+        run: npm run build
 
       - name: Upload Firefox artifact
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a  # v7.0.1

.github/workflows/lint.yml

@@ -15,17 +15,21 @@ jobs:
 
       - name: Setup Node.js
         uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e  # v6.4.0
+      - name: Install the dependencies
+        run: npm ci
+
+      # eslint
+      - name: Lint the scripts
+        run: npm run lint
 
       # web-ext
-      - name: Install web-ext
-        run: npm install --global web-ext
       - name: Display web-ext version
-        run: web-ext --version
+        run: npx web-ext --version
       # Firefox ignores Chrome's "service_worker" key and web-ext lint warns
       # about it: BACKGROUND_SERVICE_WORKER_IGNORED. Strip it before linting
       - name: Drop Chrome-only service_worker key for Firefox lint
         run: |
           jq 'del(.background.service_worker)' manifest.json > manifest.tmp
           mv manifest.tmp manifest.json
       - name: Lint the webextension
-        run: web-ext lint --warnings-as-errors
+        run: npm run lint:webext -- --warnings-as-errors

.gitignore

@@ -0,0 +1,2 @@
+node_modules/
+web-ext-artifacts/

.web-ext-config.mjs

@@ -1,5 +1,6 @@
 export default {
   ignoreFiles: [
+    'eslint.config.js',
     'package-lock.json',
     'package.json',
     'tests',

DOCUMENTATION.md

@@ -13,6 +13,7 @@ request question: instead of *"which files does this PR change?"*, it tells you
 - [Authentication](#authentication)
 - [Forges](#forges)
 - [Internationalization](#internationalization)
+- [Development](#development)
 - [Install](#install)
 - [Troubleshooting](#troubleshooting)
 
@@ -86,6 +87,10 @@ On open, the popup:
 ├── static/
 │   ├── icon-*.png         # toolbar / store icons
 │   └── icon.svg           # source icon
+├── tests/                 # test suite (node --test), one file per module
+├── package.json           # npm scripts + dev dependencies (ESLint, web-ext)
+├── eslint.config.js       # ESLint flat config
+├── .web-ext-config.mjs    # web-ext config: files to keep out of the package
 └── .github/               # CI workflows (lint, test, build) + dependabot
 ```
 
@@ -220,6 +225,23 @@ If you add a translatable string:
 - add the string to `_locales/template.json`
 - update `_locales/en/messages.json` with a description and a translation
 
+## Development
+
+The dev tools (ESLint, web-ext) are npm dev dependencies; install them once
+with `npm ci`. Then:
+
+- `npm test` — run the test suite (`npm run test:coverage` adds coverage)
+- `npm run lint` — lint the scripts with ESLint
+- `npm run lint:webext` — validate the extension with `web-ext lint`. It
+  always warns that Firefox ignores the Chrome-only
+  `background.service_worker` manifest key; the CI lint workflow strips that
+  key first and escalates any other warning to an error
+- `npm run build` — package the extension into `web-ext-artifacts/`
+  (the development files listed in `.web-ext-config.mjs` stay out)
+
+The CI workflows run the same scripts: lint and test on every push, build on
+the main branch and tags.
+
 ## Install
 ### Firefox
 

background.js

@@ -224,7 +224,7 @@ function handleUpdated(tabId, changeInfo, tabInfo) {
     }
 }
 
-async function handleRemoved(tabId, removeInfo) {
+async function handleRemoved(tabId) {
     // forget the closed tab's result
     try {
         await clearTabResult(tabId)

eslint.config.js

@@ -0,0 +1,18 @@
+import js from "@eslint/js"
+import globals from "globals"
+
+export default [
+    js.configs.recommended,
+    {
+        // extension code runs in the browser; tests run under Node
+        languageOptions: {
+            globals: globals.browser,
+        },
+    },
+    {
+        files: ["tests/**"],
+        languageOptions: {
+            globals: globals.nodeBuiltin,
+        },
+    },
+]