RFC: Add filtering behavior to whos()

[jdlangs]

This change adds a filter keyword argument to the whos methods that takes one or more types that should not be displayed. It changes the default behavior to not display Module types.

I raised this issue in #9902 but didn't get any discussion going. I don't see any real use-case of needing to see what modules have been imported into Main, and as my example in the issue shows, it can be quite a large number. I think it makes sense to keep it less cluttered and to allow the current behavior through an additional argument. Plus it allows for other interesting options like excluding Functions and/or DataTypes.

[StefanKarpinski]

Seems reasonable to me. @JeffBezanson?

[ViralBShah]

I wish we can also show memory consumption...

[jdlangs]

Just changed the default filter objects so modules are only hidden when the plain whos() is called. So whos(SomeMod) will still show exported submodules.

[jdlangs]

I figure the 3 month anniversary is as good a time as any to bring this back up.

@StefanKarpinski, @ViralBShah, any other feedback? This appears to be a case of quite limited interest.

[StefanKarpinski]

I think the functionality is useful but I'm not sure about the API. Since it's a function intended for interactive usage, however, it wouldn't be too awful to change it later if we come up with better.

[jdlangs]

I agree, it is somewhat awkward, but there's basically zero cost to changing it at any time. I'd be happy to implement other approaches.

I think there's some minor degree of importance, and not just personal preference, to having whos() not output imported modules. If I load code that brings in 20-30 (or 50...) modules, it would be a persistent annoyance to always see that list. That said, I am sure there are sometimes when you want to see the exported submodules (probably not in Main), so this was attempt to get the best of both worlds.

[StefanKarpinski]

Aside from wishing for additional features, do you have any opinions about this, @ViralBShah?

[ararslan]

I like this idea, but I agree that the API is a little funky. I actually asked a question on Stack Overflow looking for similar behavior. I'd also like to see an option for returning a symbol array rather than printing.