[video_player] Implements background playback functionality

[ArvidNy]

This pull request adds the missing implementation for background playback. This allows video_player to be used with e.g. audio_service to continue playing audio after the screen is closed or the app is move to the background. A sample implementation for testing can be found here: https://github.com/ArvidNy/video_player_audio_service

Closes flutter/flutter#62739

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[stuartmorgan-g]

Thanks for the contribution! Please see https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#changing-federated-plugins for the process to make a multi-package PR, so that our CI can run tests.

[ArvidNy]

Thanks for the link, I missed that!

I might be missing something very obvious here, but I'm not sure how to update so that the remaining checks will complete. From what I understand it fails due to a cached version of video_player_platform_interface instead of using the path-based dependency:

 Compilation failed for testPath=/b/s/w/ir/x/w/packages/packages/camera/camera/example/test/main_test.dart: ../../../video_player/video_player/lib/video_player.dart:440:34: Error: The method 'setAllowBackgroundPlayback' isn't defined for the class 'VideoPlayerPlatform'.
   - 'VideoPlayerPlatform' is from 'package:video_player_platform_interface/video_player_platform_interface.dart' ('../../../../../.pub-cache/hosted/pub.dev/video_player_platform_interface-6.3.0/lib/video_player_platform_interface.dart').
  Try correcting the name to the name of an existing method, or defining a method named 'setAllowBackgroundPlayback'.
        await _videoPlayerPlatform.setAllowBackgroundPlayback(

I can get the camera example to run locally, but only if I use direct dependencies instead of overridden dependencies.

What's the best approach here? Should I just remove the path-based dependencies for the camera example or is there another way to resolve it?

[bparrishMines]

@stuartmorgan-g It looks like dependency_overrides doesn't work for transitive dependencies: https://dart.dev/tools/pub/dependencies#dependency-overrides

Only the dependency overrides in a package's own pubspec are considered during package resolution. Dependency overrides inside any depended-on packages are ignored.

@ArvidNy You should be able to fix this by manually adding the rest of the dependencies to the failing plugins. They should look like:

dependency_overrides:
  video_player: {path: ../../../../packages/video_player/video_player}
  video_player_android: {path: ../../../../packages/video_player/video_player_android}
  video_player_avfoundation: {path: ../../../../packages/video_player/video_player_avfoundation}
  video_player_platform_interface: {path: ../../../../packages/video_player/video_player_platform_interface}
  video_player_web: {path: ../../../../packages/video_player/video_player_web}

Let me know if that works.

[stuartmorgan-g]

@stuartmorgan-g It looks like dependency_overrides doesn't work for transitive dependencies

Yes, the tooling should account for that though.

@ArvidNy You should be able to fix this by manually adding the rest of the dependencies to the failing plugins.

That shouldn't have been necessary. What command did you run, exactly, to generate what's in the PR now?

[ArvidNy]

This is the command I ran:

 dart run script/tool/bin/flutter_plugin_tools.dart make-deps-path-based --target-dependencies=video_player_platform_interface,video_player_android,video_player_avfoundation,video_player,video_player_web

[ArvidNy]

Oh, and manually adding the rest of the dependency overrides does seem to resolve the issue, at least locally. So I can push that to resolve the PR tests if there's no other obvious fix for it.

[stuartmorgan-g]

I see the issue; I've filed flutter/flutter#168538 to track it.

The best solution in the context of this PR is to revert all the non-video_player* package changes.

[ArvidNy]

I have reverted all the changes in the example files in the other packages, but for some reason the tests still fail with those packages from what I can see. Not sure what more to do. Any suggestions or is it possible to review anyway?

[stuartmorgan-g]

Ah yes, the pathified tests hit the same issue.

We can ignore those failures for review; they won't affect the ability to ultimately land the PR since once sub-PRs are split out and landed it won't happen any more.