Aaron
142 lines
4.2 KiB
Markdown
142 lines
4.2 KiB
Markdown
# Defining Entrypoints
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An "entrypoint" is any HTML, JS, or CSS file that needs to be bundled and included with the extension.
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Entrypoints may or may not be listed in the extension's `manifest.json`.
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## `/entrypoints` Directory
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In WXT, entrypoints are defined by adding a file to the `entrypoints/` directory.
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For example, a project that looks like this:
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```
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<rootDir>
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└─ entrypoints/
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├─ background.ts
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├─ content.ts
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├─ injected.ts
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└─ popup.html
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```
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would result in the following `manifest.json`:
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```json
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{
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// ...
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"manifest_version": 3,
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"action": {
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// ...
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"default_popup": "popup.html"
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},
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"background": {
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// ...
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"service_worker": "background.js"
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},
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"content_scripts": [
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{
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// ...
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"js": ["content-scripts/content.js"]
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}
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]
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}
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```
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If a file uses a special name recognized by WXT, it will be added to the manifest. In this case:
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- `popup.html` → `action.default_popup`
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- `content.ts` → `content_scripts.0.js.0`
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- `background.ts` → `background.service_worker`
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But not all entrypoints are added to the `manifest.json`. If the filename is not recognized by WXT, they are still built and included in the extension, but they are considered "unlisted" and are not apart of the manifest.
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In this case, `injected.ts` gets output to `<outdir>/injected.js` and is accessible via `browser.runtime.getURL("/injected.js")`.
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:::info
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See [`/entrypoints` folder](/entrypoints/background) documentation for a full list of recognized entrypoint filenames.
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:::
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## Entrypoint Options
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Some entrypoints, like content scripts, actions, or the background, can recieve additional options.
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In HTML files, options are listed as `meta` tags:
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```html
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<html>
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<head>
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<!-- Defining the popup's "default_icon" field -->
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<meta name="manifest.default_icon" content="{ '16': '/icon/16.png' }" />
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</head>
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</html>
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```
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In TS files, options are apart of the file's default export:
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```ts
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export default defineContentScript({
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matches: ['*://*.google.com/*'],
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runAt: 'document_start',
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main() {
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// ...
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},
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});
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```
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:::info
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For a full list of entrypoints and each of their options, see the [`/entrypoints` folder](/entrypoints/background) documentation.
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:::
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### Side Effects
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You cannot use imported variables outside the `main` function is JS entrypoints. This includes options, as shown below:
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```ts
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// entrypoints/content.ts
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import { GOOGLE_MATCHES } from '~/utils/match-patterns';
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export default defineContentScript({
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matches: GOOGLE_MATCHES,
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main() {
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// ...
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},
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});
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```
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```
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$ wxt build
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wxt build
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WXT 0.14.1
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ℹ Building chrome-mv3 for production with Vite 5.0.5
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✖ Command failed after 360 ms
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[8:55:54 AM] ERROR entrypoints/content.ts: Cannot use imported variable "GOOGLE_MATCHES" before main function. See https://wxt.dev/guide/entrypoints.html#side-effects
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```
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This throws an error because WXT needs to import each entrypoint during the build process to extract its definition (containing the `match`, `run_at`, `include`/`exclude`, etc.) to render the `manifest.json` correctly. Before loading an entrypoint, a transformation is applied to remove all imports. This prevents imported modules (local or NPM) with side-effects from running during the build process, potentially throwing an error.
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:::details Why?
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When importing your entrypoint to get its definition, the file is imported in a **_node environement_**, and doesn't have access to the `window`, `chrome`, or `browser` globals a web extension ususally has access to. If WXT doesn't remove all the imports from the file, the imported modules could try and access one of these variables, throwing an error.
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:::
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:::warning
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See [`wxt-dev/wxt#336`](https://github.com/wxt-dev/wxt/issues/336) to track the status of this bug.
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:::
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Usually, this error occurs when you try to extract options into a shared file or try to run code outside the `main` function. To fix the example from above, use litteral values when defining an entrypoint instead of importing them:
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```ts
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import { GOOGLE_MATCHES } from '~/utils/match-patterns'; // [!code --]
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export default defineContentScript({
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matches: GOOGLE_MATCHES, // [!code --]
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matches: ['*//*.google.com/*'], // [!code ++]
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main() {
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// ...
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},
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});
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```
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