From 3b916142781ae1189d12d23935132c86e5533b45 Mon Sep 17 00:00:00 2001
From: Joachim Breitner <mail@joachim-breitner.de>
Date: Wed, 17 Feb 2016 12:39:59 +0100
Subject: [PATCH] hdevtools: Preserve multi-line comments

but trim unnecessary line white space above (empty lines) and left
(commont indentation). This fixes #1700.
---
 autoload/syntastic/postprocess.vim    | 21 +++++++++++++++++++++
 syntax_checkers/haskell/hdevtools.vim |  2 +-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/autoload/syntastic/postprocess.vim b/autoload/syntastic/postprocess.vim
index 136fa589c..6f63f5b4d 100644
--- a/autoload/syntastic/postprocess.vim
+++ b/autoload/syntastic/postprocess.vim
@@ -21,6 +21,27 @@ function! syntastic#postprocess#compressWhitespace(errors) abort " {{{2
     return a:errors
 endfunction " }}}2
 
+" remove initial empty lines
+function! syntastic#postprocess#removeEmptyLines(errors) abort " {{{2
+    for e in a:errors
+        let e['text'] = substitute(e['text'], '\m^\n\+', '', '')
+    endfor
+
+    return a:errors
+endfunction " }}}2
+
+" unindent consistently
+function! syntastic#postprocess#unindent(errors) abort " {{{2
+    for e in a:errors
+        let lines = split(e['text'], '\n', 1)
+        let indent = min(map(copy(lines), 'len(matchstr(v:val,"^ \\+"))'))
+        let lines = map(lines, 'v:val[' . indent . ':]')
+        let e['text'] = join(lines, "\n")
+    endfor
+
+    return a:errors
+endfunction " }}}2
+
 " remove spurious CR under Cygwin
 function! syntastic#postprocess#cygwinRemoveCR(errors) abort " {{{2
     if has('win32unix')
diff --git a/syntax_checkers/haskell/hdevtools.vim b/syntax_checkers/haskell/hdevtools.vim
index 4b0a80fbc..b547b7cb2 100644
--- a/syntax_checkers/haskell/hdevtools.vim
+++ b/syntax_checkers/haskell/hdevtools.vim
@@ -43,7 +43,7 @@ function! SyntaxCheckers_haskell_hdevtools_GetLocList() dict
         \ 'makeprg': makeprg,
         \ 'errorformat': errorformat,
         \ 'defaults': {'vcol': 1},
-        \ 'postprocess': ['compressWhitespace'] })
+        \ 'postprocess': ['removeEmptyLines', 'unindent'] })
 endfunction
 
 call g:SyntasticRegistry.CreateAndRegisterChecker({