feat: support for partialmethod

CHANGELOG.rst

@@ -20,7 +20,8 @@ Added
 - Experimental support for sub-classing ``ArgumentParser`` to customize
   ``add_argument`` (`#661
   <https://github.com/omni-us/jsonargparse/pull/661>`__).
-
+- Support for partialmethods (`#664
+  <https://github.com/omni-us/jsonargparse/issues/664>`__).
 
 v4.36.0 (2025-01-17)
 --------------------

jsonargparse/_parameter_resolvers.py

@@ -8,7 +8,7 @@
 from contextlib import contextmanager, suppress
 from contextvars import ContextVar
 from copy import deepcopy
-from functools import partial
+from functools import partial, partialmethod
 from importlib import import_module
 from types import MethodType
 from typing import Any, Callable, Dict, List, Optional, Set, Tuple, Type, Union
@@ -102,6 +102,10 @@ def is_method(attr) -> bool:
     )
 
 
+def is_partial_method(attr) -> bool:
+    return isinstance(attr, partialmethod)
+
+
 def is_property(attr) -> bool:
     return isinstance(attr, property)
 
@@ -509,6 +513,8 @@ def get_component_and_parent(
             component = getattr(function_or_class, "__new__")
         elif is_method(attr):
             component = attr
+        elif is_partial_method(attr):
+            component = getattr(function_or_class, method_or_property)
         elif is_property(attr):
             component = attr.fget
         elif isinstance(attr, classmethod):

jsonargparse_tests/test_parameter_resolvers.py

@@ -4,6 +4,7 @@
 import inspect
 import xml.dom
 from calendar import Calendar
+from functools import partialmethod
 from random import shuffle
 from typing import Any, Callable, Dict, List, Optional, Union
 from unittest.mock import patch
@@ -33,6 +34,8 @@ def method_a(self, pma1: int, pma2: float, kma1: str = "x"):
             kma1: help for kma1
         """
 
+    partial_method_a = partialmethod(method_a, pma1=1, pma2=0.5)
+
 
 class ClassB(ClassA):
     def __init__(self, pkb1: str, kb1: int = 3, kb2: str = "4", **kwargs):
@@ -899,6 +902,14 @@ def test_get_params_some_ignored():
         assert_params(get_params(func_given_kwargs), ["p", "p1"], help=False)
 
 
+# test partial method
+def test_partialmethod():
+    ClassA.partial_method_a = partialmethod(ClassA.method_a, pma1=1, pma2=0.5)
+    assert_params(get_params(ClassA, "partial_method_a"), ["pma1", "pma2", "kma1"])
+    with source_unavailable():
+        assert_params(get_params(ClassA, "partial_method_a"), ["pma1", "pma2", "kma1"])
+
+
 # unsupported cases