I have a composer plugin that defines multiple PluginInterface classes in composer.json as mentioned in the docs.

However, there is a bug when upgrading between versions of the plugin when there are multiple classes defined.

For example, assume this is the composer.json in version 1.0.0.

{
    "name": "my/plugin",
    "version": "1.0.0",
    "autoload": {
        "psr-4": {
            "MyNamespace\\": "src/"
        }
    },
    "extra": {
        "class": [
            "MyNamespace\\FirstPlugin",
            "MyNamespace\\SecondPlugin",
            "MyNamespace\\ThirdPlugin"
        ]
    }
}

And then in 2.0.0, we consolidate the functionality into one single class:

{
    "name": "my/plugin",
    "version": "2.0.0",
    "autoload": {
        "psr-4": {
            "MyNamespace\\": "src/"
        }
    },
    "extra": {
        "class": [
            "MyNamespace\\ConsolidatedPlugin"
        ]
    }
}

When we run composer update, the 1.0.0 package is activated before it's removed, but only a reference to ThirdPlugin will be kept in $this->registeredPlugins[$package->getName()], and so only ThirdPlugin is deactivated.

Thus FirstPlugin and SecondPlugin are still called, which will cause an error if those classes aren't self-contained and depend on functionality removed in 2.0.0.

Hopefully the explanation is clear, but I can create a reproduction demo tomorrow if you'd like. I also haven't run unit tests or phpstan yet, but will wait for the workflows.