#567 Try and fix NeoVim split line handling

autoload/ale/job.vim

@@ -18,43 +18,40 @@ function! s:KillHandler(timer) abort
     call job_stop(l:job, 'kill')
 endfunction
 
-function! ale#job#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, '')
-
-        " Add the new lines.
-        call extend(a:output, a:data[1:])
-    endif
-endfunction
-
 " Note that jobs and IDs are the same thing on NeoVim.
-function! s:HandleNeoVimLines(job, callback, output, data) abort
-    call ale#job#JoinNeovimOutput(a:output, a:data)
+function! ale#job#JoinNeovimOutput(job, last_line, data, callback) abort
+    let l:lines = a:data[:-2]
 
-    for l:line in a:output
+    if len(a:data) > 1
+        let l:lines[0] = a:last_line . l:lines[0]
+        let l:new_last_line = a:data[-1]
+    else
+        let l:new_last_line = a:last_line . a:data[0]
+    endif
+
+    for l:line in l:lines
         call a:callback(a:job, l:line)
     endfor
+
+    return l:new_last_line
 endfunction
 
 function! s:NeoVimCallback(job, data, event) abort
     let l:job_info = s:job_map[a:job]
 
     if a:event ==# 'stdout'
-        call s:HandleNeoVimLines(
+        let l:job_info.out_cb_line = ale#job#JoinNeovimOutput(
         \   a:job,
-        \   ale#util#GetFunction(l:job_info.out_cb),
-        \   l:job_info.out_cb_output,
+        \   l:job_info.out_cb_line,
         \   a:data,
+        \   ale#util#GetFunction(l:job_info.out_cb),
         \)
     elseif a:event ==# 'stderr'
-        call s:HandleNeoVimLines(
+        let l:job_info.err_cb_line = ale#job#JoinNeovimOutput(
         \   a:job,
-        \   ale#util#GetFunction(l:job_info.err_cb),
-        \   l:job_info.err_cb_output,
+        \   l:job_info.err_cb_line,
         \   a:data,
+        \   ale#util#GetFunction(l:job_info.err_cb),
         \)
     else
         try
@@ -165,12 +162,12 @@ function! ale#job#Start(command, options) abort
     if has('nvim')
         if has_key(a:options, 'out_cb')
             let l:job_options.on_stdout = function('s:NeoVimCallback')
-            let l:job_info.out_cb_output = []
+            let l:job_info.out_cb_line = ''
         endif
 
         if has_key(a:options, 'err_cb')
             let l:job_options.on_stderr = function('s:NeoVimCallback')
-            let l:job_info.err_cb_output = []
+            let l:job_info.err_cb_line = ''
         endif
 
         if has_key(a:options, 'exit_cb')

test/test_line_join.vader

@@ -1,23 +1,47 @@
 Before:
-  let g:test_output = [
-  \ ['one', 'two', 'thr'],
-  \ ['ee', ''],
-  \ ['fou'],
-  \ [''],
-  \ ['r', 'five'],
-  \ [],
-  \ ['', 'six']
-  \]
+  let g:lines = []
 
-  let g:expected_result = ['one', 'two', 'three', 'four', 'five', 'six']
+  function LineCallback(job_id, line) abort
+    call add(g:lines, a:line)
+  endfunction
 
 After:
-  unlet g:test_output
-  unlet g:expected_result
+  unlet! g:last_line
+  unlet! g:lines
+  delfunction LineCallback
 
-Execute (Join the lines):
-  let joined_result = []
-  for item in g:test_output
-    call ale#job#JoinNeovimOutput(joined_result, item)
-  endfor
-  AssertEqual g:expected_result, joined_result
+Execute (ALE should pass on full lines for NeoVim):
+  let g:last_line = ale#job#JoinNeovimOutput(1, '', ['x', 'y', ''], function('LineCallback'))
+
+  AssertEqual ['x', 'y'], g:lines
+  AssertEqual '', g:last_line
+
+Execute (ALE should pass on a single long line):
+  let g:last_line = ale#job#JoinNeovimOutput(1, '', ['x'], function('LineCallback'))
+
+  AssertEqual [], g:lines
+  AssertEqual 'x', g:last_line
+
+Execute (ALE should handle just a single line of output):
+  let g:last_line = ale#job#JoinNeovimOutput(1, '', ['x', ''], function('LineCallback'))
+
+  AssertEqual ['x'], g:lines
+  AssertEqual '', g:last_line
+
+Execute (ALE should join two incomplete pieces of large lines together):
+  let g:last_line = ale#job#JoinNeovimOutput(1, 'x', ['y'], function('LineCallback'))
+
+  AssertEqual [], g:lines
+  AssertEqual 'xy', g:last_line
+
+Execute (ALE join incomplete lines, and set new ones):
+  let g:last_line = ale#job#JoinNeovimOutput(1, 'x', ['y', 'z', 'a'], function('LineCallback'))
+
+  AssertEqual ['xy', 'z'], g:lines
+  AssertEqual 'a', g:last_line
+
+Execute (ALE join incomplete lines, and set new ones, with two elements):
+  let g:last_line = ale#job#JoinNeovimOutput(1, 'x', ['y', 'z'], function('LineCallback'))
+
+  AssertEqual ['xy'], g:lines
+  AssertEqual 'z', g:last_line