Fix #4305

Author: Aster89

python/ycm/tests/vimsupport_test.py

@@ -667,6 +667,16 @@ def test_ReplaceChunk_BeyondEndOfFile( self ):
     AssertBuffersAreEqualAsBytes( [ 'first line' ], result_buffer )
 
 
+  @patch( 'vim.current.window.cursor', ( 1, 1 ) )
+  def test_ReplaceChunk_AtOneLinePastEndOfFile( self ):
+    result_buffer = VimBuffer( 'buffer', contents = [ 'first line' ] )
+    start, end = _BuildLocations( 2, 1, 2, 1 )
+    vimsupport.ReplaceChunk( start, end, 'second line', result_buffer )
+
+    AssertBuffersAreEqualAsBytes( [ 'first line', 'second line' ],
+                                result_buffer )
+
+
   @patch( 'vim.current.window.cursor', ( 1, 3 ) )
   def test_ReplaceChunk_CursorPosition( self ):
     result_buffer = VimBuffer( 'buffer', contents = [ 'bar' ] )

python/ycm/vimsupport.py

@@ -1140,6 +1140,10 @@ def ReplaceChunk( start, end, replacement_text, vim_buffer ):
   # so we convert to bytes
   replacement_lines = SplitLines( ToBytes( replacement_text ) )
 
+  if start_line >= len( vim_buffer ):
+    start_line -= 1
+    replacement_lines = [ ToBytes( vim_buffer[ -1 ] ) ] + replacement_lines
+
   # NOTE: Vim buffers are a list of unicode objects on Python 3.
   start_existing_text = ToBytes( vim_buffer[ start_line ] )[ : start_column ]
   end_line_text = ToBytes( vim_buffer[ end_line ] )