Fix #188: Revert to and older version of the Haskell linter, which works better

ale_linters/haskell/ghc.vim

@@ -1,12 +1,69 @@
 " Author: w0rp <devw0rp@gmail.com>
 " Description: ghc for Haskell files
 
+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 l:pattern = '^[^:]\+:\(\d\+\):\(\d\+\): \(.\+\)$'
+    let l:output = []
+
+    " For some reason the output coming out of the GHC through the wrapper
+    " script breaks the lines up in strange ways. So we have to join some
+    " lines back together again.
+    let l:corrected_lines = []
+
+    for l:line in a:lines
+        if len(matchlist(l:line, l:pattern)) > 0
+            call add(l:corrected_lines, l:line)
+            if l:line !~# ': error:$'
+                call add(l:corrected_lines, '')
+            endif
+        elseif l:line ==# ''
+            call add(l:corrected_lines, l:line)
+        else
+            if len(l:corrected_lines) > 0
+                if l:corrected_lines[-1] =~# ': error:$'
+                    let l:line = substitute(l:line, '\v^\s+', ' ', '')
+                endif
+                let l:corrected_lines[-1] .= l:line
+            endif
+        endif
+    endfor
+
+    for l:line in l:corrected_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,
+        \   'vcol': 0,
+        \   'col': l:match[2] + 0,
+        \   'text': l:match[3],
+        \   'type': 'E',
+        \   'nr': -1,
+        \})
+    endfor
+
+    return l:output
+endfunction
+
 call ale#linter#Define('haskell', {
 \   'name': 'ghc',
 \   'output_stream': 'stderr',
 \   'executable': 'ghc',
 \   'command': g:ale#util#stdin_wrapper . ' .hs ghc -fno-code -v0',
-\   'callback': 'ale#handlers#HandleUnixFormatAsError',
+\   'callback': 'ale_linters#haskell#ghc#Handle',
 \})
 
 call ale#linter#Define('haskell', {
@@ -14,5 +71,5 @@ call ale#linter#Define('haskell', {
 \   'output_stream': 'stderr',
 \   'executable': 'stack',
 \   'command': g:ale#util#stdin_wrapper . ' .hs stack ghc -- -fno-code -v0',
-\   'callback': 'ale#handlers#HandleUnixFormatAsError',
+\   'callback': 'ale_linters#haskell#ghc#Handle',
 \})