Add warning for Application.add_source_parser()

CHANGES

@@ -10,6 +10,7 @@ Features added
   - ``app.add_directive``
   - ``app.add_role``
   - ``app.add_generic_role``
+  - ``app.add_source_parser``
   - ``image.data_uri``
   - ``image.nonlocal_uri``
 

doc/config.rst

@@ -222,6 +222,7 @@ General configuration
    * app.add_directive
    * app.add_role
    * app.add_generic_role
+   * app.add_source_parser
    * image.data_uri
    * image.nonlocal_uri
    * ref.term

sphinx/application.py

@@ -788,6 +788,11 @@ class Sphinx(object):
 
     def add_source_parser(self, suffix, parser):
         self.debug('[app] adding search source_parser: %r, %r', (suffix, parser))
+        if suffix in self._additional_source_parsers:
+            self.warn('while setting up extension %s: source_parser for %r is '
+                      'already registered, it will be overridden' %
+                      (self._setting_up_extension[-1], suffix),
+                      type='app', subtype='add_source_parser')
         self._additional_source_parsers[suffix] = parser