BeforeInstallPrompt feature

[captainbrosset]

Learn more:

• https://developer.mozilla.org/en-US/docs/Web/API/Window/beforeinstallprompt_event
• https://developer.mozilla.org/en-US/docs/Web/Progressive_web_apps/How_to/Trigger_install_prompt#adding_an_in-app_install_ui
• https://web.dev/learn/pwa/installation-prompt#the_beforeinstallprompt_event
• https://web.dev/articles/customize-install
• https://developer.chrome.com/blog/app-install-banners-native#show_the_install_prompt

[ddbeck]

Some minor issues around names and descriptions, but BCD is giving me a little headache here.

[ddbeck]

So this is pretty interesting. In the course of trying to figure out whether there was a more specific link to use here, I got to wondering why MDN doesn't link to this spec. That turned up these PRs:

• Update beforeinstallpromptevent mdn/content#26828
• BeforeInstallPromptEvent.prompt() is non-standard mdn/browser-compat-data#19910

This puts us in a slightly awkward spot here. BCD shows unqualified support for the API, even where it departs from the spec (because it effectively pretends the spec doesn't exist). We have some options here:

• If we were to link to the spec, we're sort of implying that the Chrome and Edge support for this feature reflects support for this specification.
• Not linking to a specification at all is a difficult alternative (not least of which being that the schema requires it)—what even is the feature, at that point, if we can't point to a definition?
• We could go upstream and unroll some of Will's changes to the compat data, breaking correspondence between MDN content and BCD.
• Override BCD's status.

Or maybe something I haven't thought of yet.

[captainbrosset]

I would personally link to the spec like what's done here. There's no other spec to link to, but leave a comment saying that the only implementation that currently exists is in Chromium, and that it differs from the spec. And then, work with WICG to update the spec, which I think WICG/manifest-incubations#36 is about.

[ddbeck]

Thank you, @captainbrosset. I like your description and I'm happy with this compromise around the spec.