Added support for linting of proto files (#1098)

* Added support for linting of proto files
* Added function to get the proper protoc command

ale_linters/proto/protoc_gen_lint.vim

@@ -0,0 +1,19 @@
+" Author: Jeff Willette <jrwillette88@gmail.com>
+" Description: run the protoc-gen-lint plugin for the protoc binary
+
+function! ale_linters#proto#protoc_gen_lint#GetCommand(buffer) abort
+    let l:dirname = expand('#' . a:buffer . ':p:h')
+
+    return 'protoc'
+    \   . ' -I ' . ale#Escape(l:dirname)
+    \   . ' --lint_out=. ' . '%s'
+endfunction
+
+call ale#linter#Define('proto', {
+\   'name': 'protoc-gen-lint',
+\   'lint_file': 1,
+\   'output_stream': 'stderr',
+\   'executable': 'protoc',
+\   'command_callback': 'ale_linters#proto#protoc_gen_lint#GetCommand',
+\   'callback': 'ale#handlers#unix#HandleAsError',
+\})

doc/ale-proto.txt

@@ -0,0 +1,24 @@
+===============================================================================
+ALE Proto Integration                                         *ale-proto-options*
+
+
+===============================================================================
+Integration Information
+
+Linting of `.proto` files requires that the `protoc` binary is installed in the
+system path and that the `protoc-gen-lint` plugin for the `protoc` binary is also
+installed.
+
+To enable `.proto` file linting, update |g:ale_linters| as appropriate:
+>
+  " Enable linter for .proto files
+  let g:ale_linters = {'proto': ['protoc-gen-lint']}
+<
+===============================================================================
+protoc-gen-lint                                      *ale-proto-protoc-gen-lint*
+
+  The linter is a plugin for the `protoc` binary. As long as the binary resides
+  in the system path, `protoc` will find it.
+
+===============================================================================
+  vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl:

doc/ale.txt

@@ -134,6 +134,8 @@ CONTENTS                                                         *ale-contents*
       phpstan.............................|ale-php-phpstan|
     pod...................................|ale-pod-options|
       write-good..........................|ale-pod-write-good|
+    proto.................................|ale-proto-options|
+      protoc-gen-lint.....................|ale-proto-protoc-gen-lint|
     pug...................................|ale-pug-options|
       puglint.............................|ale-pug-puglint|
     puppet................................|ale-puppet-options|

test/command_callback/test_proto_command_callback.vader

@@ -0,0 +1,16 @@
+Before:
+  call ale#test#SetDirectory('/testplugin/test/command_callback')
+  call ale#test#SetFilename('test.proto')
+
+After:
+  Restore
+
+  call ale#test#RestoreDirectory()
+  call ale#linter#Reset()
+
+Execute(The default command should be correct):
+
+  AssertEqual
+  \ 'protoc' . ' -I ' . ale#Escape(getcwd()) . ' --lint_out=. ' . '%s',
+  \ ale_linters#proto#protoc_gen_lint#GetCommand(bufnr(''))
+