haskell_ghc_options are now added to the ghc command

ale_linters/haskell/ghc.vim

@@ -1,10 +1,18 @@
 " Author: w0rp <devw0rp@gmail.com>
 " Description: ghc for Haskell files
 
+call ale#Set('haskell_ghc_options', '-fno-code -v0')
+
+function! ale_linters#haskell#ghc#GetCommand(buffer) abort
+    return 'ghc '
+    \   . ale#Var(a:buffer, 'haskell_ghc_options')
+    \   . ' %t'
+endfunction
+
 call ale#linter#Define('haskell', {
 \   'name': 'ghc',
 \   'output_stream': 'stderr',
 \   'executable': 'ghc',
-\   'command': 'ghc -fno-code -v0 %t',
+\   'command_callback': 'ale_linters#haskell#ghc#GetCommand',
 \   'callback': 'ale#handlers#haskell#HandleGHCFormat',
 \})

doc/ale-haskell.txt

@@ -12,6 +12,16 @@ g:ale_haskell_brittany_executable           *g:ale_haskell_brittany_executable*
 
   This variable can be changed to use a different executable for brittany.
 
+===============================================================================
+ghc                                                           *ale-haskell-ghc*
+
+g:ale_haskell_ghc_options                           *g:ale_haskell_ghc_options*
+                                                    *b:ale_haskell_ghc_options*
+  Type: |String|
+  Default: `'-fno-code -v0'`
+
+  This variable can be changed to modify flags given to ghc.
+
 ===============================================================================
 hdevtools                                               *ale-haskell-hdevtools*