Get plugin corresponding to return values when calling hook

[youngmit]

Perhaps this is already possible, and I am just missing something, but is it possible to determine which plugin returned each value from a hook call? This would be valuable information for providing error messages and the like in situations where one and only one plugin should return a value under certain circumstances. Being able to report which plugins returned which values would be nice. Perhaps something like an alternative hook calling mechanism, which would return a dictionary (keyed on plugin namespace), rather than a list?

[simonw]

I'm interested in this too, also for debugging purposes. I'd like to display an HTML comment on a page that shows which plugin was responsible for returning a specific piece of information.