[CP] Fix race condition in PluginManager

[scheglov]

commit(s) to merge: 7ee2744

merge instructions: clean merge

What is the issue: A race condition, see flutter/flutter#90868 (comment)

What is the fix: Remove the plugin when it stops, but only when the expected instance stops.

Why cherrypick: This affects users of analyze plugins.

Risk: low

Link to original issue(s): flutter/flutter#90868

/cc @kevmoo @mit-mit @whesse @athomas @vsmenon @devoncarew

[devoncarew]

This affects users of analyze plugins.

What would trigger this? Does this happen over time to all plugin users? Is it triggered by things that would rebuild the analysis context?

I'm trying to get a sense for the impact here (# of users impacted, what percentage of those users, ...).

[scheglov]

This can be triggered by a change to the file system that causes re-creating analysis contexts, such as dart pub get, which updates package_config.json. When this happens, we ask each plugin to stop, then create new analysis contexts, and start (almost always the same) plugins again. And after we started new plugin instances we get this notification that the old instance stopped, so we used to forget about plugin instances.

So, after every dart pub get you get a new plugin instance. Run it 10 times, get 10 instances.

[devoncarew]

Approved -

[athomas]

Assuming this is "merge-to-stable"? The fix should be included in the next beta by default.

[devoncarew]

Yes, sorry, this is a merge-to-stable item.

[athomas]

Cherry-picked to stable in 4ac35a7 (2.14.4).