Support pkg-config-rs link_files on static/target builds

[cole-h]

I was recently working on a project that was trying to link to another project statically. The build was failing because it couldn't link to boost; when building statically, the parts of boost that were used were propagated in the Libs: of the library as a .a static archive. However, if I used pkg_config directly to directly probe libraries depending on these static archives from boost, the build started succeeding. That's when I noticed that pkg-config-rs handles this via the link_files part of their Config, but system-deps didn't!

There are a few things here that are maybe not quite Super Awesome (like the test needing to dig so deep into the test setup functions, and having to add the target arg to the gen_flags function), so if you have thoughts or opinions on how to make them better, I'd be happy to fix them!

[codecov]

Codecov Report

❌ Patch coverage is 97.41935% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.64%. Comparing base (3bb1c9e) to head (ac11ae3).

Files with missing lines	Patch %	Lines
src/lib.rs	84.61%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #137      +/-   ##
==========================================
+ Coverage   92.40%   92.64%   +0.23%     
==========================================
  Files           8        8              
  Lines        3412     3564     +152     
==========================================
+ Hits         3153     3302     +149     
- Misses        259      262       +3     

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[gdesmott]

Thanks for your patch!

I'm happy to integrate this feature but ideally would prefer to avoid copying all this code from pkg-config-rs if possible.

[gdesmott]

It's not great to have so many tricky logic copied from pkg-config-rs.

It would be great if this could be exposed as part of their API somehow. Can you open a ticket there asking if that's something they would consider?

[cole-h]

Yeah, I agree. I was going back and forth on whether or not to ask them to expose it, and ended up not, but you're right that it would be much better if they said "yes".

rust-lang/pkg-config-rs#184

[cole-h]

(Since clippy was failing, I added an expect attr that silences it for this one function, since I'd like to keep the diff from upstream as small as possible)

[cole-h]

@gdesmott Thanks again for the review, and sorry for letting this languish for so long... I completely forgot about it. However, I think I've addressed all your comments at this point. Unfortunately, there's been no movement upstream on exposing this function, though...

I submitted a PR just now that would fix the issue I submitted earlier; maybe that will be more successful: rust-lang/pkg-config-rs#192

[gdesmott]

I submitted a PR just now that would fix the issue I submitted earlier; maybe that will be more successful: rust-lang/pkg-config-rs#192

@sdroege : I see you are a maintainer of pkg-config-rs. Any chance you could give this PR a look please? :)

[gdesmott]

rust-lang/pkg-config-rs#184 has been fixed (thanks @sdroege !) so we can use this once released.

[sdroege]

I hope to have time to review some more PRs and possibly merge them before making a new release.

[cole-h]

pkg-config v0.3.34 was released earlier (thanks, @/sdroege!), which publicized Library::extract_lib_from_filename. The PR now reuses that instead of copy-pasting the implementation.

[sdroege]

@cole-h @thiblahute rust-lang/pkg-config-rs#185 might also be of interest for the things you're doing btw