Add ShaderLab language

[tgjones]

This PR adds a new language definition for ShaderLab (used to write shaders in the Unity game engine). It uses the grammar that was already added as part of #3469.

I've moved the .shader extension from the GLSL language definition (where it was incorrect, but better than nothing) to the new ShaderLab language definition.

ShaderLab search result on GitHub.com

[larsbrinkhoff]

.shader is a very generic file extension. I'm not a shader language expert; are really all those search result ShaderLab files?

[larsbrinkhoff]

I believe these keywords are present in ShaderLab but unlikely to appear in other shader languages: ColorMask, CGINCLUDE, CGPROGRAM, _MainTex, SubShader. You're right, the vast majority of all .shader files is ShaderLab.

However, some of them are GLSL.

[tgjones]

Ah, thanks for noticing that. Presumably I should add the .shader extension back to GLSL - but do I need to do anything, beyond providing samples, to help the classifier?

On a possibly related note, I think there's a bug in this classifier test:

Samples.each do |sample|
  language  = Linguist::Language.find_by_name(sample[:language])
  languages = Language.find_by_filename(sample[:path]).map(&:name)
  next unless languages.length > 1

  results = Classifier.classify(Samples.cache, File.read(sample[:path]), languages)
  assert_equal language.name, results.first[0], "#{sample[:path]}\n#{results.inspect}"
end

It never gets beyond the next unless..., because Language.find_by_filename is too specific, and only ever returns a single language. Language.find_by_extension seems to work better there, but I don't know the code well enough to know if that's the correct fix.

[pchaigno]

It never gets beyond the next unless..., because Language.find_by_filename is too specific, and only ever returns a single language. Language.find_by_extension seems to work better there, but I don't know the code well enough to know if that's the correct fix.

Nice catch! That is the correct fix :-)
I missed this test when I changed find_by_filename in #2006 :/
Could you open a separate pull request to fix it?

[larsbrinkhoff]

do I need to do anything, beyond providing samples, to help the classifier?

If the samples doesn't do the trick, lib/linguist/heuristics.rb is your friend.

[tgjones]

Could you open a separate pull request to fix it?

I've opened #3494 with a fix for the ambiguous classification test.

If the samples doesn't do the trick, lib/linguist/heuristics.rb is your friend.

It looks like the samples are enough - assuming I fixed the test correctly in #3494, and that I'm testing the right thing :)

[tgjones]

Please let me know if you need anything more from me on this PR.

[larsbrinkhoff]

Travis says the pull request doesn't pass build/test.

[tgjones]

Oops, somehow didn't notice that (or rather I did, but I looked at the build failure for a different Ruby version that had unrelated errors, and thought it wasn't caused by my changes).

Anyway, fixed now.

[larsbrinkhoff]

Looks good to me.