Fix help for Protocol types not working correctly

CHANGELOG.rst

@@ -12,6 +12,15 @@ The semantic versioning only considers the public API as described in
 paths are considered internals and can change in minor and patch releases.
 
 
+v4.35.1 (2024-12-??)
+--------------------
+
+Fixed
+^^^^^
+- Help for ``Protocol`` types not working correctly (`#645
+  <https://github.com/omni-us/jsonargparse/pull/645>`__).
+
+
 v4.35.0 (2024-12-16)
 --------------------
 

jsonargparse/_actions.py

@@ -350,18 +350,31 @@ def __init__(self, typehint=None, **kwargs):
             super().__init__(**kwargs)
 
     def update_init_kwargs(self, kwargs):
-        from ._typehints import get_optional_arg, get_subclass_names, get_unaliased_type
+        from ._typehints import (
+            get_optional_arg,
+            get_subclass_names,
+            get_subclass_types,
+            get_unaliased_type,
+            is_protocol,
+        )
 
         typehint = get_unaliased_type(get_optional_arg(self._typehint))
         if get_typehint_origin(typehint) is not Union:
             assert "nargs" not in kwargs
             kwargs["nargs"] = "?"
         self._basename = iter_to_set_str(get_subclass_names(self._typehint, callable_return=True))
+        self._baseclasses = get_subclass_types(typehint, callable_return=True)
+        assert self._baseclasses
+
+        self._kind = "subclass of"
+        if any(is_protocol(b) for b in self._baseclasses):
+            self._kind = "subclass or implementer of protocol"
+
         kwargs.update(
             {
                 "metavar": "CLASS_PATH_OR_NAME",
                 "default": SUPPRESS,
-                "help": f"Show the help for the given subclass of {self._basename} and exit.",
+                "help": f"Show the help for the given {self._kind} {self._basename} and exit.",
             }
         )
 
@@ -375,23 +388,22 @@ def print_help(self, call_args):
         from ._typehints import (
             ActionTypeHint,
             get_optional_arg,
-            get_subclass_types,
             get_unaliased_type,
+            implements_protocol,
             resolve_class_path_by_name,
         )
 
         parser, _, value, option_string = call_args
         try:
             typehint = get_unaliased_type(get_optional_arg(self._typehint))
-            baseclasses = get_subclass_types(typehint, callable_return=True)
             if self.nargs == "?" and value is None:
                 val_class = typehint
             else:
                 val_class = import_object(resolve_class_path_by_name(typehint, value))
         except Exception as ex:
             raise TypeError(f"{option_string}: {ex}") from ex
-        if not any(is_subclass(val_class, b) for b in baseclasses):
-            raise TypeError(f'{option_string}: Class "{value}" is not a subclass of {self._basename}')
+        if not any(is_subclass(val_class, b) or implements_protocol(val_class, b) for b in self._baseclasses):
+            raise TypeError(f'{option_string}: Class "{value}" is not a {self._kind} {self._basename}')
         dest = re.sub("\\.help$", "", self.dest)
         subparser = type(parser)(description=f"Help for {option_string}={get_import_path(val_class)}")
         if ActionTypeHint.is_callable_typehint(typehint) and hasattr(typehint, "__args__"):

jsonargparse/_typehints.py

@@ -1103,7 +1103,7 @@ def implements_protocol(value, protocol) -> bool:
     from jsonargparse._parameter_resolvers import get_signature_parameters
     from jsonargparse._postponed_annotations import get_return_type
 
-    if not inspect.isclass(value) or value is object:
+    if not inspect.isclass(value) or value is object or not is_protocol(protocol):
         return False
     members = 0
     for name, _ in inspect.getmembers(protocol, predicate=inspect.isfunction):

jsonargparse_tests/test_subclasses.py

@@ -1443,6 +1443,14 @@ def predict(self, items: List[float]) -> List[float]:
         return items
 
 
+class SubclassImplementsInterface(Interface):
+    def __init__(self, max_items: int):
+        self.max_items = max_items
+
+    def predict(self, items: List[float]) -> List[float]:
+        return items
+
+
 class NotImplementsInterface1:
     def predict(self, items: str) -> List[float]:
         return []
@@ -1462,6 +1470,7 @@ def predict(self, items: List[float]) -> None:
     "expected, value",
     [
         (True, ImplementsInterface),
+        (True, SubclassImplementsInterface),
         (False, ImplementsInterface(1)),
         (False, NotImplementsInterface1),
         (False, NotImplementsInterface2),
@@ -1488,14 +1497,22 @@ 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)
     init = parser.instantiate_classes(cfg)
     assert isinstance(init.cls, ImplementsInterface)
     assert init.cls.batch_size == 5
     assert init.cls.predict([1.0, 2.0]) == [1.0, 2.0]
+
+    help_str = get_parser_help(parser)
+    assert "known subclasses:" in help_str
+    assert f"{__name__}.SubclassImplementsInterface" in help_str
+    help_str = get_parse_args_stdout(parser, ["--cls.help=SubclassImplementsInterface"])
+    assert "--cls.max_items" in help_str
+    with pytest.raises(ArgumentError, match="not a subclass or implementer of protocol"):
+        parser.parse_args([f"--cls.help={__name__}.NotImplementsInterface1"])
+
     with pytest.raises(ArgumentError, match="is a protocol"):
         parser.parse_args([f"--cls={__name__}.Interface"])
     with pytest.raises(ArgumentError, match="does not implement protocol"):
@@ -1551,13 +1568,17 @@ 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)
     init = parser.instantiate_classes(cfg)
     assert isinstance(init.cls, ImplementsCallableInterface)
     assert init.cls([1.0, 2.0]) == [1.0, 2.0]
+
+    assert "known subclasses:" not in get_parser_help(parser)
+    help_str = get_parse_args_stdout(parser, [f"--cls.help={__name__}.ImplementsCallableInterface"])
+    assert "--cls.batch_size" in help_str
+
     with pytest.raises(ArgumentError, match="is a protocol"):
         parser.parse_args([f"--cls={__name__}.CallableInterface"])
     with pytest.raises(ArgumentError, match="does not implement protocol"):