Improve :YcmToggleLogs behavior

If already opened logfiles are not visible (hidden buffers or in another
tab), close them and open new ones. It fixes the issue where the command
seems to do nothing even though it actually close the non-visible logfiles.

python/ycm/vimsupport.py

@@ -671,9 +671,10 @@ def CheckFilename( filename ):
       "filename '{0}' cannot be opened. {1}".format( filename, error ) )
 
 
-def BufferExistsForFilename( filename ):
+def BufferIsVisibleForFilename( filename ):
   """Check if a buffer exists for a specific file."""
-  return GetBufferNumberForFilename( filename, False ) is not -1
+  buffer_number = GetBufferNumberForFilename( filename, False )
+  return BufferIsVisible( buffer_number )
 
 
 def CloseBuffersForFilename( filename ):
@@ -681,7 +682,11 @@ def CloseBuffersForFilename( filename ):
   buffer_number = GetBufferNumberForFilename( filename, False )
   while buffer_number is not -1:
     vim.command( 'silent! bwipeout! {0}'.format( buffer_number ) )
-    buffer_number = GetBufferNumberForFilename( filename, False )
+    new_buffer_number = GetBufferNumberForFilename( filename, False )
+    if buffer_number == new_buffer_number:
+      raise RuntimeError( "Buffer {0} for filename '{1}' should already be "
+                          "wiped out.".format( buffer_number, filename ) )
+    buffer_number = new_buffer_number
 
 
 def OpenFilename( filename, options = {} ):

python/ycm/youcompleteme.py

@@ -534,11 +534,14 @@ class YouCompleteMe( object ):
 
   def ToggleLogs( self, stdout = True, stderr = True ):
     if ( stdout and
-         vimsupport.BufferExistsForFilename( self._server_stdout ) or
+         vimsupport.BufferIsVisibleForFilename( self._server_stdout ) or
          stderr and
-         vimsupport.BufferExistsForFilename( self._server_stderr ) ):
+         vimsupport.BufferIsVisibleForFilename( self._server_stderr ) ):
       return self._CloseLogs( stdout = stdout, stderr = stderr )
 
+    # Close hidden logfile buffers if any to keep a clean state
+    self._CloseLogs( stdout = stdout, stderr = stderr )
+
     try:
       self._OpenLogs( stdout = stdout, stderr = stderr )
     except RuntimeError as error: