Join the lines Neovim passes to ale (#263)

* Join the lines Neovim passes to ale

Fixes #256

* Refactor line joining into own function

* Add test for line joining

* Fix the test. Sorry.

autoload/ale/engine.vim

@@ -72,22 +72,39 @@ function! s:StopPreviousJobs(buffer, linter) abort
     let g:ale_buffer_info[a:buffer].job_list = l:new_job_list
 endfunction
 
-function! s:GatherOutput(job, data) abort
+function! s:GatherOutputVim(channel, data) abort
+    let l:job_id = s:GetJobID(ch_getjob(a:channel))
+
+    if !has_key(s:job_info_map, l:job_id)
+        return
+    endif
+
+    call add(s:job_info_map[l:job_id].output, a:data)
+endfunction
+
+function! s:GatherOutputNeoVim(job, data, event) abort
     let l:job_id = s:GetJobID(a:job)
 
     if !has_key(s:job_info_map, l:job_id)
         return
     endif
 
-    call extend(s:job_info_map[l:job_id].output, a:data)
+    " Join the lines passed to ale, because Neovim splits them up.
+    " a:data is a list of strings, where every item is a new line, except the
+    " first one, which is the continuation of the last item passed last time.
+    call ale#engine#JoinNeovimOutput(s:job_info_map[l:job_id].output, a:data)
 endfunction
 
-function! s:GatherOutputVim(channel, data) abort
-    call s:GatherOutput(ch_getjob(a:channel), [a:data])
-endfunction
+function! ale#engine#JoinNeovimOutput(output, data) abort
+    if empty(a:output)
+        call extend(a:output, a:data)
+    else
+        " Extend the previous line, which can be continued.
+        let a:output[-1] .= get(a:data, 0, '')
 
-function! s:GatherOutputNeoVim(job, data, event) abort
-    call s:GatherOutput(a:job, a:data)
+        " Add the new lines.
+        call extend(a:output, a:data[1:])
+    endif
 endfunction
 
 function! s:HandleExit(job) abort

test/test_line_join.vader

@@ -0,0 +1,23 @@
+Before:
+  let g:test_output = [
+  \ ['one', 'two', 'thr'],
+  \ ['ee', ''],
+  \ ['fou'],
+  \ [''],
+  \ ['r', 'five'],
+  \ [],
+  \ ['', 'six']
+  \]
+
+  let g:expected_result = ['one', 'two', 'three', 'four', 'five', 'six']
+
+After:
+  unlet g:test_output
+  unlet g:expected_result
+
+Execute (Join the lines):
+  let joined_result = []
+  for item in g:test_output
+    call ale#engine#JoinNeovimOutput(joined_result, item)
+  endfor
+  AssertEqual g:expected_result, joined_result