refactor: Change signature of app.add_source_parser()

To make compatible with old versions, app.add_source_parser() have taken
two types of arguments.  But the compatibility was no longer needed
since 3.0.  So it would be better to use clearer signature.

sphinx/application.py

@@ -22,6 +22,7 @@ from typing import Any, Callable, Dict, IO, List, Optional, Tuple, Union
 
 from docutils import nodes
 from docutils.nodes import Element, TextElement
+from docutils.parsers import Parser
 from docutils.parsers.rst import Directive, roles
 from docutils.transforms import Transform
 from pygments.lexer import Lexer
@@ -1074,7 +1075,7 @@ class Sphinx:
         """
         self.registry.add_source_suffix(suffix, filetype, override=override)
 
-    def add_source_parser(self, *args: Any, **kwargs: Any) -> None:
+    def add_source_parser(self, parser: "Type[Parser]", override: bool = False) -> None:
         """Register a parser class.
 
         .. versionadded:: 1.4
@@ -1084,7 +1085,7 @@ class Sphinx:
         .. versionchanged:: 1.8
            Add *override* keyword.
         """
-        self.registry.add_source_parser(*args, **kwargs)
+        self.registry.add_source_parser(parser, override=override)
 
     def add_env_collector(self, collector: "Type[EnvironmentCollector]") -> None:
         """Register an environment collector class.

sphinx/registry.py

@@ -259,12 +259,12 @@ class SphinxComponentRegistry:
         else:
             self.source_suffix[suffix] = filetype
 
-    def add_source_parser(self, parser: "Type[Parser]", **kwargs: Any) -> None:
+    def add_source_parser(self, parser: "Type[Parser]", override: bool = False) -> None:
         logger.debug('[app] adding search source_parser: %r', parser)
 
         # create a map from filetype to parser
         for filetype in parser.supported:
-            if filetype in self.source_parsers and not kwargs.get('override'):
+            if filetype in self.source_parsers and not override:
                 raise ExtensionError(__('source_parser for %r is already registered') %
                                      filetype)
             else: