Auto merge of #2707 - micbou:fix-omnifunc-cursor-move, r=bstaletic

[READY] Restore cursor position after omnifunc call

When compiled without C-family support, YCM will use the default omnifunc from Vim (`ccomplete#Complete`) to provide semantic completion. This omnifunc calls [`searchdecl`](http://vimdoc.sourceforge.net/htmldoc/eval.html#searchdecl()) to find a declaration, which is supposed to move the cursor to that declaration. However, the cursor is not moved when called through the omni completion mapping (`CTRL-X CTRL-O`). Since PR #2657, YCM calls the omnifunc outside completion mode and thus the cursor is moved to the found declaration after typing `.` or `->`.

Considering this `searchdecl` trick may be used by other omnifuncs, we fix the issue by always restoring the cursor position after calling the omnifunc.

Fixes #2698.

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python/ycm/omni_completer.py

@@ -90,13 +90,22 @@ def ComputeCandidatesInner( self, request_data ):
       # because it affects the value returned by 'query'
       request_data[ 'start_column' ] = return_value + 1
 
+      # Calling directly the omnifunc may move the cursor position. This is the
+      # case with the default Vim omnifunc for C-family languages
+      # (ccomplete#Complete) which calls searchdecl to find a declaration. This
+      # function is supposed to move the cursor to the found declaration but it
+      # doesn't when called through the omni completion mapping (CTRL-X CTRL-O).
+      # So, we restore the cursor position after calling the omnifunc.
+      line, column = vimsupport.CurrentLineAndColumn()
+
       omnifunc_call = [ self._omnifunc,
                         "(0,'",
                         vimsupport.EscapeForVim( request_data[ 'query' ] ),
                         "')" ]
-
       items = vim.eval( ''.join( omnifunc_call ) )
 
+      vimsupport.SetCurrentLineAndColumn( line, column )
+
       if isinstance( items, dict ) and 'words' in items:
         items = items[ 'words' ]
 

python/ycm/tests/omni_completer_test.py

@@ -30,6 +30,7 @@
                                    MockVimModule, ToBytesOnPY2, VimBuffer )
 MockVimModule()
 
+from ycm import vimsupport
 from ycm.tests import YouCompleteMeInstance
 
 
@@ -621,3 +622,39 @@ def Omnifunc( findstart, base ):
         'completion_start_column': 13
       } )
     )
+
+
+@YouCompleteMeInstance( { 'cache_omnifunc': 1 } )
+def OmniCompleter_GetCompletions_RestoreCursorPositionAfterOmnifuncCall_test(
+  ycm ):
+
+  # This omnifunc moves the cursor to the test definition like
+  # ccomplete#Complete would.
+  def Omnifunc( findstart, base ):
+    if findstart:
+      return 5
+    vimsupport.SetCurrentLineAndColumn( 0, 0 )
+    return [ 'length' ]
+
+  current_buffer = VimBuffer( 'buffer',
+                              contents = [ 'String test',
+                                           '',
+                                           'test.' ],
+                              filetype = 'java',
+                              omnifunc = Omnifunc )
+
+  with MockVimBuffers( [ current_buffer ], current_buffer, ( 3, 5 ) ):
+    # Make sure there is an omnifunc set up.
+    ycm.OnFileReadyToParse()
+    ycm.SendCompletionRequest()
+    assert_that(
+      vimsupport.CurrentLineAndColumn(),
+      contains( 2, 5 )
+    )
+    assert_that(
+      ycm.GetCompletionResponse(),
+      has_entries( {
+        'completions': ToBytesOnPY2( [ 'length' ] ),
+        'completion_start_column': 6
+      } )
+    )

python/ycm/vimsupport.py

@@ -56,6 +56,12 @@ def CurrentLineAndColumn():
   return line, column
 
 
+def SetCurrentLineAndColumn( line, column ):
+  """Sets the cursor position to the 0-based line and 0-based column."""
+  # Line from vim.current.window.cursor is 1-based.
+  vim.current.window.cursor = ( line + 1, column )
+
+
 def CurrentColumn():
   """Returns the 0-based current column. Do NOT access the CurrentColumn in
   vim.current.line. It doesn't exist yet when the cursor is at the end of the