File Handling

[dbaron]

Request for Mozilla Position on an Emerging Web Specification

• Specification Title: File Handling
• Specification or proposal URL: Explainer, Repository
• Caniuse.com URL (optional):
• Bugzilla URL (optional):
• Mozillians who can provide input (optional): @annevk @bzbarsky @hsivonen @dbaron

Other information

This proposal was just submitted for TAG review, and it seems at a high level like something I'd be interested in. I haven't looked at the details yet. It's still explainer-only; no spec yet.

[annevk]

So the main use case seems to be operating on OS-level files in web applications whereby the OS knows about the relevant web application due to a prior visit of the user to that application (and whatever additional restrictions are applied on top). So instead of application -> file, you can now go file -> application, as you already could with native applications.

The bits I don't like here:

• Relying on app manifest. It's not entirely clear to me that is the way to go for all things and in particular if we get Origin Policy/Manifest there might be changes here.
• Enforcing a particular kind of URL to be generated. I don't think we should force particular URLs on applications, even if it's only the query parameters (at least not beyond ./well-known/ and friends).

It seems somewhat more natural to me that a service worker is involved here and that opens the application as appropriate and forwards the file handle to the appropriate place.

[dbaron]

In #274 @annevk is proposing a defer position here. I guess that's okay, but given that there is a good bit of activity elsewhere relating to this, e.g., in w3ctag/design-reviews#371, I tend to think it may be worth developing a real position here sooner rather than later.

[annevk]

I'm happy to keep this open until there's been another update.

The other worry I have is that creating good UI for this is hard and there might be quite bit of spam. Even with native applications it's usually pretty bad for common types.

[dbaron]

I think it's also worth noting that this has a dependency on native file system here.

[annevk]

That's defer per #154 and per https://wicg.github.io/native-file-system/ looks pretty drafty still? In that case moving ahead with defer here too seems fine to me, but up to you.

[Jaifroid]

This API is launching in Chromium browsers as of Chromium 98. Just in case that should be a trigger for considering it further now.

[FossPrime]

Support for it is being actively worked on in vscode.dev, excalidraw launched support for it during the Chrome 92 origin trial, as a Linux, CrOS, Windows and MacOS only feature, Android is notably missing.

Safari 15.2 for MacOS 12 launched expanded File System API support, which is a prerequisite for all use cases, and also missing from Firefox https://caniuse.com/mdn-api_filesystemfilehandle

I've filed an issue with caniuse to track File Handling API support.