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.

README.md

@@ -31,12 +31,15 @@ name. That seems to be the fairest way to arrange this table.
 | Bash | [-n flag](https://www.gnu.org/software/bash/manual/bash.html#index-set) |
 | Bourne Shell | [-n flag](http://linux.die.net/man/1/sh) |
 | C | [gcc](https://gcc.gnu.org/) |
-| D | [dmd](https://dlang.org/dmd-linux.html) |
+| D | [dmd](https://dlang.org/dmd-linux.html)\* |
+| Haskell | [ghc](https://www.haskell.org/ghc/)\* |
 | Fortran | [gcc](https://gcc.gnu.org/) |
 | JavaScript | [eslint](http://eslint.org/), [jscs](http://jscs.info/), [jshint](http://jshint.com/) |
 | Python | [flake8](http://flake8.pycqa.org/en/latest/) |
 | Ruby   | [rubocop](https://github.com/bbatsov/rubocop) |
 
+*\* Supported only on Unix machines via a wrapper script.*
+
 If you would like to see support for more languages and tools, please
 [create an issue](https://github.com/w0rp/ale/issues)
 or [create a pull request](https://github.com/w0rp/ale/pulls).

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',
+\})

dmd-wrapper

@@ -9,8 +9,8 @@ temp_file="$temp_file".d
 
 trap "rm $temp_file" EXIT
 
-while read line; do
-    echo "$line" >> "$temp_file"
+while read; do
+    echo "$REPLY" >> "$temp_file"
 done
 
 # Read imports from DUB.

plugin/ale/util.vim

@@ -0,0 +1,18 @@
+if exists('g:loaded_ale_util')
+    finish
+endif
+
+let g:loaded_ale_util = 1
+
+function! s:FindWrapperScript()
+    for parent in split(&runtimepath, ',')
+        " Expand the path to deal with ~ issues.
+        let path = expand(parent . '/' . 'stdin-wrapper')
+
+        if filereadable(path)
+            return path
+        endif
+    endfor
+endfunction
+
+let g:ale#util#stdin_wrapper = s:FindWrapperScript()

stdin-wrapper

@@ -0,0 +1,23 @@
+#!/bin/bash -eu
+
+# This script implements a wrapper for any program which does not accept
+# stdin input on most Unix machines. The input to the script is read to a
+# temporary file, and the first argument sets a particular file extension
+# for the temporary file.
+#
+# All of the following arguments are read as command to run.
+
+file_extension="$1"
+shift
+
+temp_file=`mktemp`
+mv "$temp_file" "$temp_file$file_extension"
+temp_file="$temp_file$file_extension"
+
+trap "rm $temp_file" EXIT
+
+while read; do
+    echo "$REPLY" >> "$temp_file"
+done
+
+"$@" "$temp_file"