Firefox support discussion (MV2, MV3)

[fregante]

Firefox doesn't yet support Manifest v3 background workers (update March 2023)_ but this build works exclusively on that. You can use this issue to discuss alternative methods of supporting both Firefox and Chrome.

Refer to these links for official MV3 support in Firefox:

• latest update: https://blog.mozilla.org/addons/2022/05/18/manifest-v3-in-firefox-recap-next-steps/

• provisional migration guide: https://extensionworkshop.com/documentation/develop/manifest-v3-migration-guide/

• tracking bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1578284

• complete roadmap: https://bugzilla.mozilla.org/showdependencytree.cgi?id=1578284&hide_resolved=1

[fregante]

The one that makes the most sense so far is a solution originally posted by @Stvad in #75 (comment)

• create 2 manifests (under /mv2/manifest.json and /mv3/manifest.json)
• Update paths in them
• add commands in package.json to deal with that
• beware the path change for the resources used via runtime.getURL (transclude-me/extension@78b529e#diff-ebd593fb607241eb184425ae1ae5b98a4c44f5ffc0355b2d0e485ad423caa29bR12)

[fregante]

Alternatively, the extension can be changed to use Manifest v2 after the build runs, originally posted in #55 (comment)

1. Run npm run build
2. In the distribution/manifest.json file, revert the same changes you see in #75:

• set manifest_version to 2
• move host_permissions items back to permissions
• restore the previous background key

3. Save that version just for Firefox

[psiinon]

Would have liked to use this repo but the lack of Firefox support is a blocker for me.
I wouldnt have minded how it was supported but manually editing files just seems too fragile to me - it indicates that Firefox support is not a priority and so I'd expect such hacks to break at short notice :(

[milangress]

@fregante I believe that since January 17, 2023 (FF 109) V3 Manifests are supported, right?

• Release Notes: https://www.mozilla.org/en-US/firefox/109.0/releasenotes/
• Migration Guide: https://extensionworkshop.com/documentation/develop/manifest-v3-migration-guide/

Do you think it makes sense to reintroduce the polyfill? #88

[fregante]

I believe that since January 17, 2023 (FF 109) V3 Manifests are supported, right?

1. Firefox still does not support background workers: https://bugzilla.mozilla.org/show_bug.cgi?id=1573659
2. Chrome refuses to load a manifest that specifies both backgrounds scripts and workers.
   • Proposal: declaring background scripts in a neutral way w3c/webextensions#282 (comment)
3. Parcel doesn't recognize background scripts in MV3 yet (edit: fixed)
   • Background scripts for Firefox result in build error when using Manifest V3 parcel-bundler/parcel#8785

These issues mean that there's still no way to build a cross-browser extension with a single manifest.json.

Do you think it makes sense to reintroduce the polyfill? #88

The polyfill is no longer needed because Chrome also has promisified APIs in MV3. You can just use chrome.* APIs in every browser.

[fregante]

By the way, Firefox now accepts MV3 extensions, with the exception that background workers are not supported (background scripts are).

I think that Parcel 2.9 supports setting both background.worker and background.script in the manifest, but Chrome will reject such manifest.

In short, you can now build cross-browser MV3 extensions:

• set both background.worker and background.script in your manifest
• remove background.script before opening the extension in Chrome.

[fregante]

Maybe we're close here. It seems that Chrome 121 will finally allow background.scripts in its manifest (just allow, not use):

• Proposal: declaring background scripts in a neutral way w3c/webextensions#282 (comment)

This means that it will finally be possible restore Firefox support by this template:

• Add a background script for Firefox
• Restore all mentions to Firefox support in the docs and deployment

Schedule for Chrome 121:

Tue, Jan 23, 2024

[aspiers]

I note that https://github.com/Jonghakseo/chrome-extension-boilerplate-react-vite/ (which is another extension template) takes a slightly different approach of specifying the manifest in manifest.js and then automatically generating manifest.json from that, in the process converting it to be Firefox-capable when building for Firefox.

Is it worth considering a similar approach here, or are we close enough to being able to craft a single manifest.json which works with both that it's not worth changing course now?

[fregante]

Given that Chrome 121 is out, this should already work out of the box, just specify background.scripts and make sure you're using the latest parcel version

[fregante]

We're just blocked by Parcel at the moment:

• [webextensions] Parcel doesn't accept manifest v3 with both service_worker and scripts parcel-bundler/parcel#9458

I forgot I already tried it:

• Restore Firefox support #97

[fregante]

If anyone is already using the template and is looking to add support for Firefox, use the latest version of Parcel and restore the background.scripts array in the manifest file.

npm i -D @parcel/config-webextension@canary parcel@canary

See the PR #97