Improve elm linter (#637)

* Improve elm linter

Some types of errors do not return nice JSON.
Show them on the first line instead of showing nothing.

* Remove unnecessary properties from elm linter

* Add a vader test for elm-make linter

* Test non-JSON elm-make errors are shown

ale_linters/elm/make.vim

@@ -5,6 +5,7 @@ function! ale_linters#elm#make#Handle(buffer, lines) abort
     let l:output = []
     let l:is_windows = has('win32')
     let l:temp_dir = l:is_windows ? $TMP : $TMPDIR
+    let l:unparsed_lines = []
     for l:line in a:lines
         if l:line[0] ==# '['
             let l:errors = json_decode(l:line)
@@ -20,7 +21,6 @@ function! ale_linters#elm#make#Handle(buffer, lines) abort
 
                 if l:file_is_buffer
                     call add(l:output, {
-                    \    'bufnr': a:buffer,
                     \    'lnum': l:error.region.start.line,
                     \    'col': l:error.region.start.column,
                     \    'type': (l:error.type ==? 'error') ? 'E' : 'W',
@@ -29,9 +29,20 @@ function! ale_linters#elm#make#Handle(buffer, lines) abort
                     \})
                 endif
             endfor
+        elseif l:line !=# 'Successfully generated /dev/null'
+            call add(l:unparsed_lines, l:line)
         endif
     endfor
 
+    if len(l:unparsed_lines) > 0
+        call add(l:output, {
+        \    'lnum': 1,
+        \    'type': 'E',
+        \    'text': l:unparsed_lines[0],
+        \    'detail': join(l:unparsed_lines, "\n")
+        \})
+    endif
+
     return l:output
 endfunction