[regression] Project-level plugin dependencies ignored for direct CLI invocation if plugin key uses properties

I have a plugin that makes use of the implementation attribute in its configuration. That is, one of its parameters is a plexus tag that specifies an implementation class to use.

The implementation class comes from a jar that is the plugin's dependency, but that dependency is included as part of the plugin configuration, not as part of the stock plugin.

This setup works fine when I bind the plugin's configuration via an execution to a normal phase (generate-sources as it happens).

When I bind the plugin's configuration to the default-cli execution, plexus cannot configure the component, claiming that the classname it encounters in the "implementation" attribute cannot be found (even though, again, if I bind it to the generate-sources phase instead, via another execution, same configuration, everything works fine.

I tried to debug this using mvn -X, but the output was totally baffling; sorry. My raw take is that it looks like dependency resolution in the default-cli execution is somehow performed differently than when the plugin is run bound to a phase.