Add hamllint linter for Haml (#377)

* Add hamllint linter for Haml

* Simplify hamllint

README.md

@@ -71,6 +71,7 @@ name. That seems to be the fairest way to arrange this table.
 | Erlang | [erlc](http://erlang.org/doc/man/erlc.html) |
 | Fortran | [gcc](https://gcc.gnu.org/) |
 | Go | [gofmt -e](https://golang.org/cmd/gofmt/), [go vet](https://golang.org/cmd/vet/), [golint](https://godoc.org/github.com/golang/lint), [go build](https://golang.org/cmd/go/) |
+| Haml | [haml-lint](https://github.com/brigade/haml-lint)
 | Haskell | [ghc](https://www.haskell.org/ghc/), [hlint](https://hackage.haskell.org/package/hlint) |
 | HTML | [HTMLHint](http://htmlhint.com/), [proselint](http://proselint.com/), [tidy](http://www.html-tidy.org/) |
 | Java | [javac](http://www.oracle.com/technetwork/java/javase/downloads/index.html) |

ale_linters/haml/hamllint.vim

@@ -0,0 +1,33 @@
+" Author: Patrick Lewis - https://github.com/patricklewis
+" Description: haml-lint for Haml files
+
+function! ale_linters#haml#hamllint#Handle(buffer, lines) abort
+    " Matches patterns like the following:
+    " <path>:51 [W] RuboCop: Use the new Ruby 1.9 hash syntax.
+    let l:pattern = '\v^.*:(\d+) \[([EW])\] (.+)$'
+    let l:output = []
+
+    for l:line in a:lines
+        let l:match = matchlist(l:line, l:pattern)
+
+        if len(l:match) == 0
+            continue
+        endif
+
+        call add(l:output, {
+        \   'bufnr': a:buffer,
+        \   'lnum': l:match[1] + 0,
+        \   'type': l:match[2],
+        \   'text': l:match[3]
+        \})
+    endfor
+
+    return l:output
+endfunction
+
+call ale#linter#Define('haml', {
+\   'name': 'hamllint',
+\   'executable': 'haml-lint',
+\   'command': 'haml-lint %t',
+\   'callback': 'ale_linters#haml#hamllint#Handle'
+\})

doc/ale.txt

@@ -91,6 +91,7 @@ The following languages and tools are supported.
 * Erlang: 'erlc'
 * Fortran: 'gcc'
 * Go: 'gofmt -e', 'go vet', 'golint', 'go build'
+* Haml: 'hamllint'
 * Haskell: 'ghc', 'hlint'
 * HTML: 'HTMLHint', 'proselint', 'tidy'
 * Java: 'javac'