Improve file globbing logic (fixes #5057)

[mitchellwrosen]

I tested this change manually by running cabal sdist on https://github.com/RyanGlScott/cabal-sdist-bug/tree/910078306b4e127996bd7c9208a7e741b9f74351:

$ cabal sdist
Building source dist for cabal-sdist-bug-0.1.0...
Source tarball created: dist/cabal-sdist-bug-0.1.0.tar.gz

[hvr]

This likely also needs a cabal check, as old cabals will choke.

[hvr]

• needs tests (& make sure that the documented limitations for * in filenames remain in place).
• possibly a cabal check compat-warning
• changelog
• possibly user guide update (to document that starting with version x.y, fileglobbing supports multi-part extensions)

see also #5057 (comment)

[mitchellwrosen]

Sorry, I'm unclear on which came first, these TODOs or your comment about how the current behavior was actually intended. Should I close this PR?

[23Skidoo]

That behaviour was intended originally, but there seems to be a consensus that we should relax it a bit.

[mitchellwrosen]

I've added a test and updated changelog. Could I have some guidance on these remaining TODOs?

(& make sure that the documented limitations for * in filenames remain in place).

What are the documented limitations for * in filenames?

possibly a cabal check compat-warning

What does this mean?

possibly user guide update (to document that starting with version x.y, fileglobbing supports multi-part extensions)

Where is the user guide located?

Thanks!

[phadej]

I'm really sorry that we (me and @hvr) are demanding. I try to explain:

---

possibly a cabal check compat-warning`

run cabal check. The implementation of that is in Distribution.PackageDescription.Check.
There is e.g. check use of "data-files: data/*.txt" syntax.

The issue is that:

• the change is good for ergonomics
• but if someone else developing the package would use older cabal-install, their cabal sdist won't pick all the files, resulting in broken package.
  • unfortunately there isn't cabal check which checks that globs actually pick at least some files. There should be.
  • new version should warn, that 'extended globbing' is needed, and cabal-version is too low.
    • that's tricky, but doable

The scenario is not that different to #5073:
if some CI setup (for any reason) uses older cabal-install for some job, than cabal sdist will produce broken tarballs, resulting in confusingly failing builds.

Where is the user guide located?

Cabal/doc