Move _deep_merge to _io.py to avoid duplication

Copilot · nathanjmcdougall · Copilot · commit c93b4791797d · 2026-03-20T21:35:34.000Z
Co-authored-by: nathanjmcdougall <18602289+nathanjmcdougall@users.noreply.github.com> Agent-Logs-Url: https://github.com/usethis-python/usethis-python/sessions/ee88789e-37df-4ed0-95b9-b5149bf1b2ee
diff --git a/src/usethis/_file/toml/io_.py b/src/usethis/_file/toml/io_.py
@@ -2,7 +2,6 @@
 
 import copy
 import re
-from collections.abc import MutableMapping
 from typing import TYPE_CHECKING, Any
 
 import tomlkit.api
@@ -27,6 +26,7 @@
     KeyValueFileManager,
     UnexpectedFileIOError,
     UnexpectedFileOpenError,
+    _deep_merge,
     print_keys,
 )
 
@@ -354,26 +354,6 @@ def remove_from_list(self, *, keys: Sequence[Key], values: Collection[Any]) -> N
         self.commit(toml_document)
 
 
-def _deep_merge(
-    target: MutableMapping[Any, Any], source: MutableMapping[Any, Any]
-) -> MutableMapping[Any, Any]:
-    """Recursively merge source into target in place, returning target.
-
-    For keys present in both mappings, if both values are mappings the merge is
-    applied recursively; otherwise the source value replaces the target value.
-    """
-    for key, value in source.items():
-        if (
-            key in target
-            and isinstance(target[key], MutableMapping)
-            and isinstance(value, MutableMapping)
-        ):
-            _deep_merge(target[key], value)
-        else:
-            target[key] = value
-    return target
-
-
 def _set_value_in_existing(
     *,
     toml_document: TOMLDocument,
diff --git a/src/usethis/_file/yaml/io_.py b/src/usethis/_file/yaml/io_.py
@@ -2,7 +2,6 @@
 
 import copy
 import re
-from collections.abc import MutableMapping
 from contextlib import contextmanager
 from dataclasses import dataclass
 from io import StringIO
@@ -30,6 +29,7 @@
     KeyValueFileManager,
     UnexpectedFileIOError,
     UnexpectedFileOpenError,
+    _deep_merge,
     print_keys,
 )
 
@@ -375,26 +375,6 @@ def remove_from_list(self, *, keys: Sequence[Key], values: list[Any]) -> None:
         self.commit(self._content)
 
 
-def _deep_merge(
-    target: MutableMapping[Any, Any], source: MutableMapping[Any, Any]
-) -> MutableMapping[Any, Any]:
-    """Recursively merge source into target in place, returning target.
-
-    For keys present in both mappings, if both values are mappings the merge is
-    applied recursively; otherwise the source value replaces the target value.
-    """
-    for key, value in source.items():
-        if (
-            key in target
-            and isinstance(target[key], MutableMapping)
-            and isinstance(value, MutableMapping)
-        ):
-            _deep_merge(target[key], value)
-        else:
-            target[key] = value
-    return target
-
-
 def _set_value_in_existing(
     *, content: YAMLLiteral, keys: Sequence[Key], value: Any
 ) -> None:
diff --git a/src/usethis/_io.py b/src/usethis/_io.py
@@ -2,7 +2,8 @@
 
 import re
 from abc import abstractmethod
-from typing import TYPE_CHECKING, Generic, TypeAlias, TypeVar
+from collections.abc import MutableMapping
+from typing import TYPE_CHECKING, Any, Generic, TypeAlias, TypeVar
 
 from typing_extensions import assert_never
 
@@ -13,7 +14,7 @@
     from collections.abc import Sequence
     from pathlib import Path
     from types import TracebackType
-    from typing import Any, ClassVar
+    from typing import ClassVar
 
     from typing_extensions import Self
 
@@ -246,3 +247,23 @@ def print_keys(keys: Sequence[Key]) -> str:
             assert_never(key)
 
     return ".".join(components)
+
+
+def _deep_merge(
+    target: MutableMapping[Any, Any], source: MutableMapping[Any, Any]
+) -> MutableMapping[Any, Any]:
+    """Recursively merge source into target in place, returning target.
+
+    For keys present in both mappings, if both values are mappings the merge is
+    applied recursively; otherwise the source value replaces the target value.
+    """
+    for key, value in source.items():
+        if (
+            key in target
+            and isinstance(target[key], MutableMapping)
+            and isinstance(value, MutableMapping)
+        ):
+            _deep_merge(target[key], value)
+        else:
+            target[key] = value
+    return target
