Fix confusing error message when CLI is used with a class that define…

…s a subcommand method (#430 comment).

CHANGELOG.rst

@@ -19,6 +19,9 @@ Fixed
 ^^^^^
 - ``argcomplete`` not working when type and choices given (`#442
   <https://github.com/omni-us/jsonargparse/issues/442>`__).
+- Confusing error message when ``CLI`` is used with a class that defines a
+  ``subcommand`` method (`#430 comment
+  <https://github.com/omni-us/jsonargparse/issues/430#issuecomment-1903974112>`__).
 
 
 v4.27.3 (2024-01-26)

jsonargparse/_actions.py

@@ -604,6 +604,8 @@ def add_subcommand(self, name, parser, **kwargs):
         """
         if parser._subparsers is not None:
             raise ValueError("Multiple levels of subcommands must be added in level order.")
+        if self.dest == name:
+            raise ValueError(f"A subcommand name can't be the same as the subcommands dest: '{name}'.")
 
         parser.prog = f"{self._prog_prefix} [options] {name}"
         parser.env_prefix = f"{self.env_prefix}{name}_"

jsonargparse/_cli.py

@@ -151,23 +151,24 @@ def _add_subcommands(
 def _add_component_to_parser(component, parser, as_positional, fail_untyped, config_help):
     kwargs = dict(as_positional=as_positional, fail_untyped=fail_untyped, sub_configs=True)
     if inspect.isclass(component):
-        subcommand_keys = [k for k, v in inspect.getmembers(component) if callable(v) and k[0] != "_"]
-        if not subcommand_keys:
+        class_methods = [k for k, v in inspect.getmembers(component) if callable(v) and k[0] != "_"]
+        if not class_methods:
             added_args = parser.add_class_arguments(component, as_group=False, **kwargs)
             if not parser.description:
                 parser.description = get_help_str(component, parser.logger)
             return added_args
         added_args = parser.add_class_arguments(component, **kwargs)
         subcommands = parser.add_subcommands(required=True)
-        for key in subcommand_keys:
-            description = get_help_str(getattr(component, key), parser.logger)
+        for method in class_methods:
+            method_object = getattr(component, method)
+            description = get_help_str(method_object, parser.logger)
             subparser = type(parser)(description=description)
             subparser.add_argument("--config", action=ActionConfigFile, help=config_help)
-            added_subargs = subparser.add_method_arguments(component, key, as_group=False, **kwargs)
-            added_args += [f"{key}.{a}" for a in added_subargs]
+            added_subargs = subparser.add_method_arguments(component, method, as_group=False, **kwargs)
+            added_args += [f"{method}.{a}" for a in added_subargs]
             if not added_subargs:
                 remove_actions(subparser, (ActionConfigFile, _ActionPrintConfig))
-            subcommands.add_subcommand(key, subparser, help=get_help_str(getattr(component, key), parser.logger))
+            subcommands.add_subcommand(method, subparser, help=get_help_str(method_object, parser.logger))
     else:
         added_args = parser.add_function_arguments(component, as_group=False, **kwargs)
         if not parser.description:

jsonargparse_tests/test_cli.py

@@ -34,6 +34,17 @@ def test_unexpected_components(components):
         CLI(components)
 
 
+class ConflictingSubcommandKey:
+    def subcommand(self, x: int = 0):
+        return x
+
+
+def test_conflicting_subcommand_key():
+    with pytest.raises(ValueError) as ctx:
+        CLI(ConflictingSubcommandKey, args=["subcommand", "--x=1"])
+    assert ctx.match("subcommand name can't be the same")
+
+
 # single function tests