Added support for OrderedDict as a type

CHANGELOG.rst

@@ -19,6 +19,7 @@ Added
 ^^^^^
 - Support for ``MappingProxyType`` as a type and as default for mapping types
   (`#540 <https://github.com/omni-us/jsonargparse/pull/540>`__).
+- Support for ``OrderedDict`` as a type.
 - New function ``get_loader`` to get the current loader for a given parser mode
   (`#479 comment
   <https://github.com/omni-us/jsonargparse/issues/479#issuecomment-2022596544>`__,

DOCUMENTATION.rst

@@ -400,9 +400,9 @@ Some notes about this support are:
   :ref:`restricted-strings` and paths and URLs as explained in sections
   :ref:`parsing-paths` and :ref:`parsing-urls`.
 
-- ``Dict``, ``Mapping``, ``MutableMapping``, ``MappingProxyType``, and
-  ``TypedDict`` are supported but only with ``str`` or ``int`` keys. For more
-  details see :ref:`dict-items`.
+- ``Dict``, ``Mapping``, ``MutableMapping``, ``MappingProxyType``,
+  ``OrderedDict`` and ``TypedDict`` are supported but only with ``str`` or
+  ``int`` keys. For more details see :ref:`dict-items`.
 
 - ``Tuple``, ``Set`` and ``MutableSet`` are supported even though they can't be
   represented in json distinguishable from a list. Each ``Tuple`` element

jsonargparse/_namespace.py

@@ -1,6 +1,7 @@
 """Classes and functions related to namespace objects."""
 
 import argparse
+from collections import OrderedDict
 from contextlib import contextmanager
 from typing import (
     Any,
@@ -72,7 +73,7 @@ def strip_meta(cfg):
 
 def recreate_branches(data, skip_keys=None):
     new_data = data
-    if isinstance(data, (Namespace, dict)):
+    if isinstance(data, (Namespace, dict)) and not isinstance(data, OrderedDict):
         new_data = type(data)()
         for key, val in getattr(data, "__dict__", data).items():
             if skip_keys is None or key not in skip_keys:

jsonargparse/_typehints.py

@@ -4,7 +4,7 @@
 import os
 import re
 from argparse import ArgumentError
-from collections import abc, defaultdict
+from collections import OrderedDict, abc, defaultdict
 from contextlib import contextmanager, suppress
 from contextvars import ContextVar
 from copy import deepcopy
@@ -120,6 +120,7 @@
     MutableMapping,
     abc.Mapping,
     abc.MutableMapping,
+    OrderedDict,
     Callable,
     abc.Callable,
 }
@@ -145,7 +146,16 @@
     abc.Sequence,
     abc.MutableSequence,
 }
-mapping_origin_types = {Dict, dict, Mapping, MappingProxyType, MutableMapping, abc.Mapping, abc.MutableMapping}
+mapping_origin_types = {
+    Dict,
+    dict,
+    Mapping,
+    MappingProxyType,
+    MutableMapping,
+    abc.Mapping,
+    abc.MutableMapping,
+    OrderedDict,
+}
 callable_origin_types = {Callable, abc.Callable}
 
 literal_types = {Literal}
@@ -904,8 +914,10 @@ def adapt_typehints(
                 raise_unexpected_value(f"Unexpected keys: {extra_keys}", val)
             for k, v in val.items():
                 val[k] = adapt_typehints(v, typehint.__annotations__[k], **adapt_kwargs)
-        if typehint_origin == MappingProxyType and not serialize:
+        if typehint_origin is MappingProxyType and not serialize:
             val = MappingProxyType(val)
+        elif typehint_origin is OrderedDict:
+            val = dict(val) if serialize else OrderedDict(val)
 
     # Callable
     elif typehint_origin in callable_origin_types or typehint in callable_origin_types:

jsonargparse_tests/test_typehints.py

@@ -6,6 +6,7 @@
 import time
 import uuid
 from calendar import Calendar, TextCalendar
+from collections import OrderedDict
 from enum import Enum
 from pathlib import Path
 from types import MappingProxyType
@@ -563,6 +564,26 @@ def test_mapping_default_mapping_proxy_type(parser):
     assert parser.dump(cfg, format="json") == '{"mapping":{"x":1}}'
 
 
+@pytest.mark.skipif(sys.version_info < (3, 9), reason="OrderedDict subscriptable since python 3.9")
+def test_ordered_dict(parser):
+    parser.add_argument("--odict", type=eval("OrderedDict[str, int]"))
+    cfg = parser.parse_args(['--odict={"a":1, "b":2}'])
+    assert isinstance(cfg.odict, OrderedDict)
+    assert OrderedDict([("a", 1), ("b", 2)]) == cfg.odict
+    with pytest.raises(ArgumentError) as ctx:
+        parser.parse_args(['--odict={"x":"-"}'])
+    ctx.match("Expected a <class 'int'>")
+    assert parser.dump(cfg, format="json") == '{"odict":{"a":1,"b":2}}'
+    assert parser.dump(cfg, format="yaml") == "odict:\n  a: 1\n  b: 2\n"
+
+
+def test_dict_default_ordered_dict(parser):
+    parser.add_argument("--dict", type=dict, default=OrderedDict({"a": 1}))
+    defaults = parser.get_defaults()
+    assert isinstance(defaults.dict, OrderedDict)
+    assert defaults.dict == {"a": 1}
+
+
 # union tests