Add support for checking Haskell code via a wrapper script which can be used for other tools, and fix a readline problem with the DMD wrapper script.

ale_linters/haskell/ghc.vim

@@ -0,0 +1,59 @@
+if exists('g:loaded_ale_linters_haskell_ghc')
+    finish
+endif
+
+let g:loaded_ale_linters_haskell_ghc = 1
+
+function! ale_linters#haskell#ghc#Handle(buffer, lines)
+    " Look for lines like the following.
+    "
+    " /dev/stdin:28:26: Not in scope: `>>>>>'
+    let pattern = '^[^:]\+:\(\d\+\):\(\d\+\): \(.\+\)$'
+    let output = []
+
+    " For some reason the output coming out of the GHC through the wrapper
+    " script breaks the lines up in strange ways. So we have to join some
+    " lines back together again.
+    let corrected_lines = []
+
+    for line in a:lines
+        if len(matchlist(line, pattern)) > 0
+            call add(corrected_lines, line)
+            call add(corrected_lines, '')
+        elseif line == ''
+            call add(corrected_lines, line)
+        else
+            if len(corrected_lines) > 0
+                let corrected_lines[-1] .= line
+            endif
+        endif
+    endfor
+
+    for line in corrected_lines
+        let l:match = matchlist(line, pattern)
+
+        if len(l:match) == 0
+            continue
+        endif
+
+        call add(output, {
+        \   'bufnr': a:buffer,
+        \   'lnum': l:match[1] + 0,
+        \   'vcol': 0,
+        \   'col': l:match[2] + 0,
+        \   'text': l:match[3],
+        \   'type': 'E',
+        \   'nr': -1,
+        \})
+    endfor
+
+    return output
+endfunction
+
+call ALEAddLinter('haskell', {
+\   'name': 'ghc',
+\   'output_stream': 'stderr',
+\   'executable': 'ghc',
+\   'command': g:ale#util#stdin_wrapper . ' .hs ghc -fno-code -v0',
+\   'callback': 'ale_linters#haskell#ghc#Handle',
+\})