Force filename completer on #include

plugin/youcompleteme.vim

@@ -89,7 +89,7 @@ let g:ycm_add_preview_to_completeopt =
       \ get( g:, 'ycm_add_preview_to_completeopt', 0 )
 
 let g:ycm_complete_in_comments_and_strings =
-      \ get( g:, 'ycm_complete_in_comments_and_strings', 0 )
+      \ get( g:, 'ycm_complete_in_comments_and_strings', 1 )
 
 let g:ycm_collect_identifiers_from_comments_and_strings =
       \ get( g:, 'ycm_collect_identifiers_from_comments_and_strings', 0 )

python/completers/cpp/clang_completer.py

@@ -331,3 +331,8 @@ def ClangAvailableForBuffer( buffer_object ):
   filetypes = vimsupport.FiletypesForBuffer( buffer_object )
   return any( [ filetype in CLANG_FILETYPES for filetype in filetypes ] )
 
+
+def InCFamilyFile():
+  return any( [ filetype in CLANG_FILETYPES for filetype in
+                vimsupport.CurrentFiletypes() ] )
+

python/completers/general/filename_completer.py

@@ -17,6 +17,7 @@
 # along with YouCompleteMe.  If not, see <http://www.gnu.org/licenses/>.
 
 from completers.threaded_completer import ThreadedCompleter
+from completers.cpp.clang_completer import InCFamilyFile
 import vim
 import vimsupport
 import os
@@ -47,9 +48,17 @@ class FilenameCompleter( ThreadedCompleter ):
       \\.)*$
       """, re.X )
 
+    self._include_regex = re.compile( '^\s*#(?:include|import)\s*(?:"|<)$' )
+
+
+  def AtIncludeStatmentStart( self, start_column ):
+    return ( InCFamilyFile() and
+             self._include_regex.match( vim.current.line[ :start_column ] ) )
+
 
   def ShouldUseNowInner( self, start_column ):
-    return vim.current.line[ start_column - 1 ] == '/'
+    return ( vim.current.line[ start_column - 1 ] == '/' or
+             self.AtIncludeStatmentStart( start_column ) )
 
 
   def SupportedFiletypes( self ):