Changes as follows below:

Moved representers to support.py
Moved OrderedDict logic to its own representer

src/uwtools/config/formats/yaml.py

@@ -1,3 +1,4 @@
+from collections import OrderedDict
 from pathlib import Path
 from types import SimpleNamespace as ns
 from typing import Optional
@@ -6,7 +7,13 @@
 import yaml
 
 from uwtools.config.formats.base import Config
-from uwtools.config.support import INCLUDE_TAG, TaggedString, log_and_error, represent_namelist
+from uwtools.config.support import (
+    INCLUDE_TAG,
+    TaggedString,
+    log_and_error,
+    represent_namelist,
+    represent_ordereddict,
+)
 from uwtools.utils.file import FORMAT, readable, writable
 
 _MSGS = ns(
@@ -46,6 +53,8 @@ def __repr__(self) -> str:
         The string representation of a YAMLConfig object.
         """
         yaml.add_representer(TaggedString, TaggedString.represent)
+        yaml.add_representer(f90nml.namelist.Namelist, represent_namelist)
+        yaml.add_representer(OrderedDict, represent_ordereddict)
         return yaml.dump(self.data, default_flow_style=False).strip()
 
     # Private methods
@@ -118,6 +127,7 @@ def dump_dict(cfg: dict, path: Optional[Path] = None) -> None:
         """
         yaml.add_representer(TaggedString, TaggedString.represent)
         yaml.add_representer(f90nml.namelist.Namelist, represent_namelist)
+        yaml.add_representer(OrderedDict, represent_ordereddict)
         with writable(path) as f:
             yaml.dump(cfg, f, sort_keys=False)
 

src/uwtools/config/support.py

@@ -4,6 +4,7 @@
 from importlib import import_module
 from typing import Dict, Type, Union
 
+import f90nml  # type: ignore
 import yaml
 
 from uwtools.exceptions import UWConfigError
@@ -54,6 +55,36 @@ def log_and_error(msg: str) -> Exception:
     return UWConfigError(msg)
 
 
+def represent_namelist(dumper: yaml.Dumper, data: f90nml.Namelist) -> yaml.nodes.MappingNode:
+    """
+    Convert f90 Namelist objects to ordered dicts and serialize.
+
+    :param dumper: The YAML dumper.
+    :param data: The f90nml Namelist to serialize.
+    """
+    # Convert the f90nml Namelist to an ordered dictionary
+    namelist_dict = data.todict()
+
+    # Represent the dictionary as a YAML mapping
+    return dumper.represent_mapping("tag:yaml.org,2002:map", namelist_dict)
+
+
+def represent_ordereddict(dumper: yaml.Dumper, data: OrderedDict) -> yaml.nodes.MappingNode:
+    """
+    Convert ordered dict objects to dictionaries and serialize.
+
+    :param dumper: The YAML dumper.
+    :param data: The ordereddict to serialize.
+    """
+    # Convert the Ordered Dict to a dictionary
+    for key, value in data.items():
+        if isinstance(value, OrderedDict):
+            data[key] = dict(value)
+
+    # Represent the dictionary as a YAML mapping
+    return dumper.represent_mapping("tag:yaml.org,2002:map", data)
+
+
 class TaggedString:
     """
     A class supporting custom YAML tags specifying type conversions.
@@ -89,17 +120,3 @@ def represent(dumper: yaml.Dumper, data: TaggedString) -> yaml.nodes.ScalarNode:
         documentation for details.
         """
         return dumper.represent_scalar(data.tag, data.value)
-
-
-def represent_namelist(dumper: yaml.Dumper, data) -> yaml.nodes.MappingNode:
-    """
-    Serialize f90nml tags.
-    """
-    # Convert the f90nml Namelist object to a dictionary
-    namelist_dict = data.todict()
-    for key, value in namelist_dict.items():
-        if isinstance(value, OrderedDict):
-            namelist_dict[key] = dict(value)
-
-    # Represent the dictionary as a YAML mapping
-    return dumper.represent_mapping("tag:yaml.org,2002:map", namelist_dict)

src/uwtools/tests/config/test_support.py

@@ -4,6 +4,7 @@
 """
 
 import logging
+from collections import OrderedDict
 
 import f90nml  # type: ignore
 import pytest
@@ -58,11 +59,17 @@ def test_log_and_error(caplog):
 
 
 def test_represent_namelist():
-    yaml.add_representer(f90nml.namelist.Namelist, support.represent_namelist)
     namelist = f90nml.reads("&namelist\n key = value\n/\n")
     assert yaml.dump(namelist, default_flow_style=True).strip() == "{namelist: {key: value}}"
 
 
+def test_represent_ordereddict():
+    ordereddict_values = OrderedDict([("example", OrderedDict([("key", "value")]))])
+    assert (
+        yaml.dump(ordereddict_values, default_flow_style=True).strip() == "{example: {key: value}}"
+    )
+
+
 class Test_TaggedString:
     """
     Tests for class uwtools.config.support.TaggedString.