YcmCompleter FixIt, Move function body out-of-line Error

[djmallum]

Calling YcmCompleter FixIt on a function with a definition in a header file fails with the error below is there isn't space at the end of the .cpp file does not have space. If I open the .cpp file and add two blank lines and try again, it is successful. It doesn't work with only one blank line.

I've edited the error to be more or less anonymous, since it included file paths. I use Plugged even though the main instructions say to use vundle (only because I was previously using Plugged).

Error:

1: Move function body to out-of-line
Type number and <Enter> or click with the mouse (q or empty cancels): Error detected while processing function <SNR>68_CompleterCommand:
line    1:
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/path-to-file/plugged/YouCompleteMe/python/ycm/youcompleteme.py", line 472, in SendCommandRequest
    return SendCommandRequest(
      final_arguments,
      modifiers,
      self._user_options[ 'goto_buffer_command' ],
      extra_data )
  File "/path-to-file/plugged/YouCompleteMe/python/ycm/client/command_request.py", line 241, in SendCommandRequest
    request.RunPostCommandActionsIfNeeded( modifiers, buffer_command )
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/path-to-file/plugged/YouCompleteMe/python/ycm/client/command_request.py", line 99, in RunPostCommandActionsIfNeeded
    return self._HandleFixitResponse()
           ~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/path-to-file/plugged/YouCompleteMe/python/ycm/client/command_request.py", line 198, in _HandleFixitResponse
    vimsupport.ReplaceChunks(
    ~~~~~~~~~~~~~~~~~~~~~~~~^
      chosen_fixit[ 'chunks' ],
      ^^^^^^^^^^^^^^^^^^^^^^^^^
      silent = self._command == 'Format' )
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/path-to-file/plugged/YouCompleteMe/python/ycm/vimsupport.py", line 1042, in ReplaceChunks
    locations.extend( ReplaceChunksInBuffer( chunks_by_file[ filepath ],
                      ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                                             vim.buffers[ buffer_num ] ) )
                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/path-to-file/plugged/YouCompleteMe/python/ycm/vimsupport.py", line 1087, in ReplaceChunksInBuffer
    return reversed( [ ReplaceChunk( chunk[ 'range' ][ 'start' ],
                       ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                                     chunk[ 'range' ][ 'end' ],
                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^
                                     chunk[ 'replacement_text' ],
                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                                     vim_buffer )
                                     ^^^^^^^^^^^^
  File "/path-to-file/plugged/YouCompleteMe/python/ycm/vimsupport.py", line 1144, in ReplaceChunk
    start_existing_text = ToBytes( vim_buffer[ start_line ] )[ : start_column ]
                                   ~~~~~~~~~~^^^^^^^^^^^^^^
IndexError: line number out of range

[Aster89]

Same error here here, but with Haskell file, so there's most likely nothing language-specific.

The repro is:

1. Open a file with the following content (it will give two warings on the two instance lines):

   data Set a = Set
   
   instance Semigroup (Set a) where
   
   instance Monoid (Set a) where

2. Load the Haskell langauge server (I do it by :source ~/lsp-examples/vimrc.generated, which has this content:

   let g:ycm_lsp_dir = '/home/enrico/lsp-examples'
   let g:ycm_language_server = []
   let g:ycm_language_server += [
         \   {
         \     'name': 'haskell-language-server',
         \     'cmdline': [ 'haskell-language-server-wrapper', '--lsp' ],
         \     'filetypes': [ 'haskell', 'lhaskell' ],
         \     'project_root_files': [ 'stack.yaml', 'package.yaml', 'hie.yaml' ]
         \   }
         \ ]

3. Attempt :YcmCompleter FixIt on the line with Monoid.

Outcome:

• Step 3 will error like in the original report above.
• Doing the same on the line with Semigroup doesn't error.
• Making the line with Monoid not the last line (i.e. by adding a line after it) fixes the problem.
• Incidentally, when doing :YcmCompleter FixIt on the line with Semigroup (which succeeds), quite a few empty lines are inserted after the fix, which I don't know if it's what HLS indeed requested, or it's part of the bug in YCM.

Below is a screencast of the workflow to repro the error:

[Aster89]

I think the bug is at ReplaceChunk, here:

YouCompleteMe/python/ycm/vimsupport.py

Line 1119 in 131b182

def ReplaceChunk( start, end, replacement_text, vim_buffer ):

Indeed, the failure happens here:

YouCompleteMe/python/ycm/vimsupport.py

Line 1144 in 131b182

start_existing_text = ToBytes( vim_buffer[ start_line ] )[ : start_column ]

where vim_buffer[ start_line ] fails because start_line == len(vim_buffer).

I think the following test demonstrates the issue:

  @patch( 'vim.current.window.cursor', ( 1, 1 ) )
  def test_Foo( self ):
    result_buffer = VimBuffer( 'buffer', contents = [ 'first line' ] )  # LINE
    start, end = _BuildLocations( 2, 1, 2, 1 )
    vimsupport.ReplaceChunk( start, end, 'second line', result_buffer )

    AssertBuffersAreEqualAsBytes( [ 'first line', 'second line' ],
                                result_buffer )

If on # LINE one changes [ 'first line' ], to [ 'first line', '' ], then the test passes, as I showed in the screencast and wrote above:

• Making the line with Monoid not the last line (i.e. by adding a line after it) fixes the problem.

[djmallum]

I'm having some trouble with the code that I used to get the error in the first place (unrelated to YCM) so I am unable to see if this fixes the specific error I was having. But once I get that fixed I can see if I can reproduce this error again and then try this fix you've suggested.