Add ruby.NewGemSpecCataloger to DirectoryCatalogers.

[evanchaoli]

I have a use case that needs to run Syft scan inside a Dockerfile. But I found that installed Ruby Gems couldn't be found. So I have to use --catalogers=all.

Then I noticed that ruby.NewGemSpecCataloger() is not included in DirectoryCatalogers.

But I also noticed that python.NewPythonPackageCataloger() is in the list, I think PythonPackage is the same place as RubyGemSpec, so I feel it's reasonable to add ruby.NewGemSpecCataloger to DirectoryCatalogers.

[wagoodman]

Hey! I think doing this is a good idea, however, a little more work would be needed. Today the current gemspec cataloger looks at gemspecs that are installed within a specifications directory (which is done when installing a gem via the CLI).

https://github.com/anchore/syft/blob/main/syft/pkg/cataloger/ruby/catalogers.go#L19

Another constructor for the same cataloger would be needed that looks for gemspecs in any location, something like:

// the existing one today, renamed...
func NewInstalledGemSpecCataloger() *generic.Cataloger {
	return generic.NewCataloger("ruby-gemspec-cataloger").
		WithParserByGlobs(parseGemSpecEntries, "**/specifications/**/*.gemspec")
}

// new one with a more broad glob...
func NewGemSpecCataloger() *generic.Cataloger {
	return generic.NewCataloger("ruby-gemspec-cataloger").
		WithParserByGlobs(parseGemSpecEntries, "**/*.gemspec")
}

[evanchaoli]

@wagoodman Thanks for your comment. I wonder why do we need a broader glob? In my case, --catalogers=all has worked around. Will *.gemspec files exist under other directories than "specifications"?

[willmurphyscode]

Will *.gemspec files exist under other directories than "specifications"?

@evanchaoli yes, one example might be scanning the directory when a Gem's source code is checked out - we'd expected to have a *.gemspec in the root.

#2128 has some more information. If you'd like, reworking this PR to fix #2128 would be greatly appreciated.

[willmurphyscode]

@evanchaoli did I answer your question adequately? Please let me know if there's anything I can do to help here.

[evanchaoli]

Hey @willmurphyscode I just haven't got bandwidth to get back to this PR. I will try to do something next week.

[evanchaoli]

Hey @wagoodman, finally I got back to this PR. Please take a look at the new diff.