Fixed dump not working for partial callable with return instance pytorch-lightning#15340 (comment).

Author: mauvilsa

CHANGELOG.rst

@@ -12,6 +12,16 @@ The semantic versioning only considers the public API as described in
 paths are considered internals and can change in minor and patch releases.
 
 
+v4.20.1 (2023-02-??)
+--------------------
+
+Fixed
+^^^^^
+- Dump not working for partial callable with return instance
+  `pytorch-lightning#15340 (comment)
+  <https://github.com/Lightning-AI/lightning/issues/15340#issuecomment-1439203008>`__.
+
+
 v4.20.0 (2023-02-20)
 --------------------
 
@@ -54,7 +64,6 @@ v4.19.0 (2022-12-27)
 
 Added
 ^^^^^
-- ``add_dataclass_arguments`` now supports the ``fail_untyped`` parameter
 - ``CLI`` now supports the ``fail_untyped`` and ``parser_class`` parameters.
 - ``bytes`` and ``bytearray`` registered on first use and decodes from standard
   Base64.

jsonargparse/typehints.py

@@ -722,7 +722,8 @@ def adapt_typehints(
     elif typehint_origin in callable_origin_types or typehint in callable_origin_types:
         if serialize:
             if is_subclass_spec(val):
-                val = adapt_class_type(val, True, False, sub_add_kwargs)
+                val, _, num_partial_args = adapt_partial_callable_class(typehint, val)
+                val = adapt_class_type(val, True, False, sub_add_kwargs, skip_args=num_partial_args)
             else:
                 val = object_path_serializer(val)
         else:

jsonargparse_tests/test_typehints.py

@@ -838,6 +838,8 @@ def __init__(self, *args, **kwargs):
             self.assertIsInstance(optim, Adam)
             self.assertEqual(optim.params, [4.5, 6.7])
             self.assertEqual(optim.lr, 0.01)
+            dump = parser.dump(cfg)
+            self.assertEqual(yaml.safe_load(dump), cfg.as_dict())
 
             self.assertEqual(cfg, parser.parse_args(['--optimizer=Adam', '--optimizer.lr=0.01']))