Compatibility debugging

[fonsp]

In addition to #2582, @staticfloat also proposed adding "compatibility debugging" features to IDEs (like Pluto.jl): if a package has a more recent version but it cannot be installed, show the user why not (i.e. which other direct dep is holding it back).

I think that this is also valuable directly in the Pkg REPL. For example:

pkg> add Revise
... Revise 2 added! ...

pkg> # hmmm I heard that Revise 3 is available, let's try update!

pkg> update Revise
... No changes to Manifest ...
... Revise 3 is available but Example restricts it to 2 ...

Currently, I can achieve this by copying my environment to a temporary directory, and calling add [email protected] (if 3.2.1 is latest according to the registry). The resulting error message will be the debugging information I need. However, like in #2582, a "dry run" option to Pkg.add would be very useful, allowing me to quickly call Pkg.add without downloading source or binaries.

In the future, perhaps this behaviour can be implemented into Pkg itself?

[KristofferC]

I did some WIP here #2284. Might be able to take something from there.

[KristofferC]

Closed by #2284

[fonsp]

Thanks, awesome! Would it be easy to expose this through API, so that we can use it in Pluto?

[KristofferC]

You can probably use the status_compat_info as an API and then display the result of that.