Simplify and fix DecimalAnnotation

beanie/odm/custom_types/decimal.py

@@ -1,47 +1,18 @@
-# check python version
+import decimal
 import sys
 
+import bson
+import pydantic
+
 if sys.version_info >= (3, 9):
     from typing import Annotated
 else:
     from typing_extensions import Annotated
 
-from decimal import Decimal as NativeDecimal
-from typing import Any, Callable
-
-from bson import Decimal128
-from pydantic import GetJsonSchemaHandler
-from pydantic.fields import FieldInfo
-from pydantic.json_schema import JsonSchemaValue
-from pydantic_core import core_schema
-
-
-class DecimalCustomAnnotation:
-    @classmethod
-    def __get_pydantic_core_schema__(
-        cls,
-        _source_type: Any,
-        _handler: Callable[[Any], core_schema.CoreSchema],  # type: ignore
-    ) -> core_schema.CoreSchema:  # type: ignore
-        def validate(value, _: FieldInfo) -> NativeDecimal:
-            if isinstance(value, Decimal128):
-                return value.to_decimal()
-            return value
-
-        python_schema = core_schema.general_plain_validator_function(validate)  # type: ignore
-
-        return core_schema.json_or_python_schema(
-            json_schema=core_schema.float_schema(),
-            python_schema=python_schema,
-        )
-
-    @classmethod
-    def __get_pydantic_json_schema__(
-        cls,
-        _core_schema: core_schema.CoreSchema,  # type: ignore
-        handler: GetJsonSchemaHandler,
-    ) -> JsonSchemaValue:
-        return handler(core_schema.float_schema())
-
 
-DecimalAnnotation = Annotated[NativeDecimal, DecimalCustomAnnotation]
+DecimalAnnotation = Annotated[
+    decimal.Decimal,
+    pydantic.BeforeValidator(
+        lambda v: v.to_decimal() if isinstance(v, bson.Decimal128) else v
+    ),
+]

tests/odm/custom_types/test_decimal_annotation.py

@@ -0,0 +1,16 @@
+from decimal import Decimal
+
+from beanie.odm.utils.pydantic import IS_PYDANTIC_V2
+from tests.odm.models import DocumentWithDecimalField
+
+
+def test_decimal_deserialize():
+    m = DocumentWithDecimalField(amt=Decimal("1.4"))
+    if IS_PYDANTIC_V2:
+        m_json = m.model_dump_json()
+        m_from_json = DocumentWithDecimalField.model_validate_json(m_json)
+    else:
+        m_json = m.json()
+        m_from_json = DocumentWithDecimalField.parse_raw(m_json)
+    assert isinstance(m_from_json.amt, Decimal)
+    assert m_from_json.amt == Decimal("1.4")