Fix help incorrectly showing protocols in known subclasses (#638)

CHANGELOG.rst

@@ -23,6 +23,8 @@ Fixed
   <https://github.com/omni-us/jsonargparse/pull/625>`__).
 - Callable protocols failing to parse (`#637
   <https://github.com/omni-us/jsonargparse/pull/637>`__).
+- Help incorrectly showing protocols in known subclasses (`#638
+  <https://github.com/omni-us/jsonargparse/pull/638>`__).
 
 
 v4.34.0 (2024-11-08)

jsonargparse/_typehints.py

@@ -1267,7 +1267,7 @@ def add_subclasses(cl):
             return
         if is_local(cl) or is_subclass(cl, LazyInitBaseClass):
             return
-        if not (inspect.isabstract(cl) or is_private(class_path)):
+        if not (inspect.isabstract(cl) or is_private(class_path) or is_protocol(cl)):
             if class_path in subclass_list:
                 return
             subclass_list.append(class_path)

jsonargparse_tests/test_subclasses.py

@@ -1485,6 +1485,7 @@ def test_is_instance_or_supports_protocol(expected, value):
 
 def test_parse_implements_protocol(parser):
     parser.add_argument("--cls", type=Interface)
+    assert "known subclasses:" not in get_parser_help(parser)
     cfg = parser.parse_args([f"--cls={__name__}.ImplementsInterface", "--cls.batch_size=5"])
     assert cfg.cls.class_path == f"{__name__}.ImplementsInterface"
     assert cfg.cls.init_args == Namespace(batch_size=5)
@@ -1547,6 +1548,7 @@ def test_implements_callable_protocol(expected, value):
 
 def test_parse_implements_callable_protocol(parser):
     parser.add_argument("--cls", type=CallableInterface)
+    assert "known subclasses:" not in get_parser_help(parser)
     cfg = parser.parse_args([f"--cls={__name__}.ImplementsCallableInterface", "--cls.batch_size=7"])
     assert cfg.cls.class_path == f"{__name__}.ImplementsCallableInterface"
     assert cfg.cls.init_args == Namespace(batch_size=7)