[many] Remove references to v1 embedding

[gmackall]

#6923 is a follow up pr that includes more migration steps. Both will be required to build after v1 embedding classes are removed.

I have a WIP effort to remove the v1 embedding entirely (flutter/flutter#146523 is the latest pr).

registerWith references the v1 embedding, which has been deprecated for many years, so this PR removes it from all plugins.

Also removes some additional references, see in particular these three commits:

1. Modifies private ActivityState class to remove PluginRegistry.Registrar member in image_picker: c2e4c87
2. Replaces FlutterMain.getLookupKeyForAsset() with FlutterLoader.getLookupKeyForAsset() in google_maps plugin: 73c3de3
3. Removes deprecated RegistrarFlutterAssetManager class in webview_flutter: cc842c6

Fixes flutter/flutter#70923

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[gmackall]

cc @stuartmorgan I was unaware that we had recommended folks include the static registerWith, for compatibility with v1 apps, until recently.

This means that the deletion of the v1 embedding will be a breaking change for most plugins, though the solution is simply to remove that static method.

Do you have any opinions on: how to make this the least painful/would you LGTM the deletion in the first place/would you want to keep the interface needed around, so we can have a sort of no-op registerWith while we advise people to delete it?

[stuartmorgan]

It's been a while since I was in conversations around the v1 wind-down, so I don't have all the context any more. What's the current state of v1 support on stable? IIRC the last I had been involved it was being moved behind a flag, but it was still possible to use that flag to force build an app in v1 mode. Is that still the case?

The way I would want this to go is:

• Make v1 fully impossible to use on the tool side (may already be done).
• Once that's on stable, we can delete the v1 support from all of our plugins (updating the min supported Flutter version if necessary).
• We can also do outreach to top plugins at that point to let them know they can remove it as well.

I think I'd like to keep registerWith in the interface, with a prominent comment saying it will never be called and is only there to avoid breaking compilation of plugin, for a while; it should be pretty low-impact for us to keep just that declaration. Eventually we could remove it and break plugins on master, but it would be good to have that be a while after all the big plugins (including ours) have had a chance to remove it.

[gmackall]

What's the current state of v1 support on stable?

Currently still possible to build a v1 app by passing a flag (will error without the flag), though that will change in the next release (once flutter/flutter#144726 gets picked up).

For full transparency we have been attempting to approach it faster, as a flat out deletion rather than wind down, given how long the v1 has been deprecated at this point. But this particular case seems like it will require more messaging before deletion is possible, given our own recommendations put plugin authors in this situation.

I think I'd like to keep registerWith in the interface

To be a little nitpicky, registerWith itself isn't in the interface, it is just an additional static method we have recommended people include. But (if people follow our recommendation) that static method references the inner type io.flutter.plugin.common.PluginRegistry.Registrar, which is part of the v1 embedding.

But I'm fine leaving that interface around (with a comment warning it is slated for deletion) for a release to give plugin authors time to migrate, while deleting the rest of the v1 embedding now. Does that sound reasonable to you? Also I'm happy to help reach out to the top plugin authors, if we have a list somewhere.

[gmackall]

Also in light of

Once that's on stable, we can delete the v1 support from all of our plugins (updating the min supported Flutter version if necessary).

I'll get this pr to tests passing, and then leave it around until the next release before requesting review.

[stuartmorgan]

For full transparency we have been attempting to approach it faster, as a flat out deletion rather than wind down

Right, I was thinking of the entire process of "fully supported" to "completely gone" when I say wind-down. I've been involved in discussions on and off since very early in the process.

To be a little nitpicky, registerWith itself isn't in the interface, it is just an additional static method we have recommended people include. But (if people follow our recommendation) that static method references the inner type io.flutter.plugin.common.PluginRegistry.Registrar, which is part of the v1 embedding.

Ah, that's more unfortunate in terms of code volume. But since it's just an interface we could strip out all the comments and at least get it down to a pretty small amount.

But I'm fine leaving that interface around (with a comment warning it is slated for deletion) for a release to give plugin authors time to migrate, while deleting the rest of the v1 embedding now. Does that sound reasonable to you?

Yes, I'm on board with that. The main thing I had pushed back on in the past was deleting the v1 support from our plugins while the tool still supported v1 builds, because it seemed backward. It's much smoother if we delete things from the tool up (just as we do with dropping old OS versions).

Also I'm happy to help reach out to the top plugin authors, if we have a list somewhere.

I'll get an updated list and do the outreach once the change hits stable; it's not that long a list so I can do it pretty quickly.

[johnmccutchan]

I'm not sure I understand why we aren't landing this PR now.

0. The code has been removed from flutter tool.
1. There are no tests in this repository (or any repository) that are testing the functionality of v1 embedder.
2. The Android v1 embedder has been broken since July 2023 (I intentionally didn't implement necessary functionality)

Why are we keeping dead and untested code around in our repository?

[stuartmorgan]

I'm not sure I understand why we aren't landing this PR now.

0. The code has been removed from flutter tool.

According to this comment it's been removed on master, but not stable. We have an explicit policy in this repository of supporting stable for our packages.

1. There are no tests in this repository (or any repository) that are testing the functionality of v1 embedder.

Not having tests for v1 here doesn't mean we can intentionally break v1 support. It's in the same category as "best effort" OS support.

2. The Android v1 embedder has been broken since July 2023 (I intentionally didn't implement necessary functionality)

Can you elaborate on what "broken" means, concretely? What happens, right now, if someone attempts to build an app on stable with the v1 flag?

[johnmccutchan]

I'm not sure I understand why we aren't landing this PR now.

0. The code has been removed from flutter tool.

According to this comment it's been removed on master, but not stable. We have an explicit policy in this repository of supporting stable for our packages.

1. There are no tests in this repository (or any repository) that are testing the functionality of v1 embedder.

Not having tests for v1 here doesn't mean we can intentionally break v1 support. It's in the same category as "best effort" OS support.

This is an API that was deprecated 5+ years ago and has no users.

2. The Android v1 embedder has been broken since July 2023 (I intentionally didn't implement necessary functionality)

Can you elaborate on what "broken" means, concretely? What happens, right now, if someone attempts to build an app on stable with the v1 flag?

The app will build but fail at runtime.

[stuartmorgan]

This is an API that [...] and has no users.
[...]
The app will build but fail at runtime.

Both of these things are completely new information to me. Is there more information on this somewhere?