new command: spack pkg grep to search package files

[tgamblin]

It's very common for us to tell users to grep through the existing Spack packages to find examples of what they want, and it's also very common for package developers to do it. Now, searching packages is even easier.

spack pkg grep runs grep on all package.py files in repos known to Spack. It has no special options other than the search string; all options passed to it are forwarded along to grep.

> spack pkg grep --help
usage: spack pkg grep [--help] ...

positional arguments:
  grep_args  arguments for grep

options:
  --help     show this help message and exit

Examples:

> spack pkg grep CMakePackage | head -3
/Users/gamblin2/src/spack/var/spack/repos/builtin/packages/3dtk/package.py:class _3dtk(CMakePackage):
/Users/gamblin2/src/spack/var/spack/repos/builtin/packages/abseil-cpp/package.py:class AbseilCpp(CMakePackage):
/Users/gamblin2/src/spack/var/spack/repos/builtin/packages/accfft/package.py:class Accfft(CMakePackage, CudaPackage):

> spack pkg grep -Eho '(\S*)\(PythonPackage\)' | head -3
AwsParallelcluster(PythonPackage)
Awscli(PythonPackage)
Bueno(PythonPackage)

Return value

This retains the return value semantics of grep:

• 0 for found,
• 1 for not found

• 1 for error

Choosing a grep

You can set the SPACK_GREP environment variable to choose the grep executable this command should use.

[adamjstewart]

Interesting! This is obviously something I do daily. I currently have a csv alias that Cd's to Spack's Var directory, then I run grep from there. This is slightly quicker.

This is up there with spack edit and spack unit-test in the sense that it's a tiny shortcut on top of a normal shell command. I don't think it's too ridiculous to add, doesn't have a ton of overhead to maintain, and non-power users can just ignore it. So it's fine by me.

[alalazo]

Agree completely with @adamjstewart review

[alalazo]

...but tests must pass first! 😆

[trws]

Looks good if tests pass. Only thing I'd request, if we're doing this maybe allow the user to specify the name of their grep command? Mainly to deal with things like ggpep as default name for gnu grep on mac, wanting egrep or pt or whatever for different flags etc.

[adamjstewart]

For @trws's suggestion, maybe we could rely on a SPACK_GREP env var like we do for spack edit?

[trws]

I like that idea, it's similar to how FZF and others normally handle it so it would be convenient to add to existing environment setups that pick a grep for other tools.

[tgamblin]

@trws added

[adamjstewart]

Works for me!

[alalazo]

@trws @adamjstewart If you want to have a final look this LGTM