feat: add configs merge

Author: cuinixam

src/py_app_dev/core/config.py

@@ -0,0 +1,31 @@
+from typing import Any, TypeVar
+
+from mashumaro import DataClassDictMixin
+from mashumaro.config import BaseConfig
+
+
+class BaseConfigDictMixin(DataClassDictMixin):
+    class Config(BaseConfig):
+        # When serializing to dict, omit fields with value None
+        omit_none = True
+
+
+TConfig = TypeVar("TConfig", bound="BaseConfigDictMixin")
+
+
+def deep_merge(base_dict: dict[Any, Any], new_dict: dict[Any, Any]) -> dict[Any, Any]:
+    """Recursively merge two dictionaries, where values in new_dict override values in base_dict."""
+    result: dict[Any, Any] = {}
+    for key, value in base_dict.items():
+        result[key] = value
+    for key, value in new_dict.items():
+        if key in result and isinstance(result[key], dict) and isinstance(value, dict):
+            result[key] = deep_merge(result[key], value)
+        else:
+            result[key] = value
+    return result
+
+
+def merge_configs(base: TConfig, override: TConfig) -> TConfig:
+    merged = deep_merge(base.to_dict(), override.to_dict())
+    return base.__class__.from_dict(merged)

tests/test_config.py

@@ -0,0 +1,49 @@
+from dataclasses import dataclass
+from typing import Any
+
+from py_app_dev.core.config import BaseConfigDictMixin, deep_merge, merge_configs
+
+
+@dataclass
+class SampleConfig(BaseConfigDictMixin):
+    name: str | None = None
+    retries: int = 0
+    nested: dict[str, Any] | None = None
+
+
+def test_deep_merge():
+    base = {"a": 1, "b": {"x": 1, "y": 2}, "c": 3}
+    new = {"b": {"y": 200, "z": 300}, "d": 4}
+
+    merged = deep_merge(base, new)
+
+    assert merged == {
+        "a": 1,  # preserved
+        "b": {"x": 1, "y": 200, "z": 300},  # nested merged
+        "c": 3,  # preserved
+        "d": 4,  # added
+    }
+
+
+def test_merge_configs_preserves_subclass_and_merges():
+    base = SampleConfig(name="service", retries=1, nested={"x": 1, "y": {"a": 10}})
+    override = SampleConfig(retries=5, nested={"y": {"b": 20}, "z": 99})
+
+    merged = merge_configs(base, override)
+
+    assert isinstance(merged, SampleConfig)
+
+    assert merged.name == "service", "Name should be preserved"
+    assert merged.retries == 5, "Retries should be overridden"
+    assert merged.nested == {"x": 1, "y": {"a": 10, "b": 20}, "z": 99}
+
+
+def test_merge_configs_override_none_value():
+    base = SampleConfig(name=None, retries=2, nested={"k": 1})
+    override = SampleConfig(name="final", nested=None)
+
+    merged = merge_configs(base, override)
+
+    assert merged.name == "final", "Name should be taken from override"
+    assert merged.nested == {"k": 1}, "Nested should not be overridden by None"
+    assert merged.retries == 0, "Retries should be taken from the default value in override"