feat: TransformingUnicodeAttribute now transforms python strings upon direct access

Author: AppSolves

fastapi_users_db_dynamodb/attributes.py

@@ -1,10 +1,15 @@
+from __future__ import annotations
+
 from collections.abc import Callable
+from typing import Any, TypeVar, overload
 
-from aiopynamodb.attributes import Attribute, UnicodeAttribute
+from aiopynamodb.attributes import _T, Attribute, UnicodeAttribute
 from aiopynamodb.constants import STRING
 
 from ._generics import UUID_ID
 
+_A = TypeVar("_A", bound="TransformingUnicodeAttribute")
+
 
 class GUID(Attribute[UUID_ID]):
     """
@@ -63,6 +68,22 @@ def __init__(self, transform: Callable[[str], str] | None = None, **kwargs):
         super().__init__(**kwargs)
         self.transform = transform
 
+    @overload
+    def __get__(self: _A, instance: None, owner: Any) -> _A: ...
+    @overload
+    def __get__(self: _A, instance: Any, owner: Any) -> _T: ...  # type: ignore
+    def __get__(self: _A, instance: Any, owner: Any) -> _A | _T:  # type: ignore
+        if instance:
+            attr_name = instance._dynamo_to_python_attrs.get(
+                self.attr_name, self.attr_name
+            )
+            value = instance.attribute_values.get(attr_name, None)
+            if getattr(self, "transform", None) and value is not None:
+                return self.transform(value)  # type: ignore
+            return value
+        else:
+            return self
+
     def serialize(self, value):
         """Serialize a value for later storage in DynamoDB.
 

tests/conftest.py

@@ -1,3 +1,4 @@
+import hashlib
 import uuid
 from typing import Any
 
@@ -83,3 +84,13 @@ def user_id() -> UUID4:
         UUID4: The random UUIDv4 user id.
     """
     return uuid.uuid4()
+
+
+def hash_string(string: str) -> str:
+    """A simple function that returns the SHA256 hash of a given string.
+    Args:
+        string (str): The string to hash.
+    Returns:
+        str: The SHA256 hash of the string.
+    """
+    return hashlib.sha256(string.encode("utf-8")).hexdigest()

tests/test_misc.py

@@ -4,9 +4,11 @@
 from fastapi_users_db_dynamodb import DynamoDBBaseUserTable, config
 from fastapi_users_db_dynamodb._generics import classproperty
 from fastapi_users_db_dynamodb.access_token import DynamoDBBaseAccessTokenTable
-from fastapi_users_db_dynamodb.attributes import GUID
+from fastapi_users_db_dynamodb.attributes import GUID, TransformingUnicodeAttribute
 from fastapi_users_db_dynamodb.tables import delete_tables, ensure_tables_exist
 
+from .conftest import hash_string
+
 
 class NotAModel:
     """A class representing an invalid `Model`."""
@@ -23,6 +25,9 @@ class IncompleteModel(Model):
 class ValidModel(Model):
     """A class representing a valid `Model`."""
 
+    attr = TransformingUnicodeAttribute(transform=str.lower)
+    attr2 = TransformingUnicodeAttribute(transform=hash_string)
+
     class Meta:
         """The required `Meta` definitions for PynamoDB.
 
@@ -128,3 +133,12 @@ def test_attributes(user_id):
 
     assert id.deserialize(None) is None
     assert user_id == id.deserialize(user_id)
+
+    assert ValidModel().attr is None
+    model = ValidModel(attr="TEST", attr2="TEST")
+    assert model.attr == "test"
+    model.attr = "ANOTHER TEST"
+    assert model.attr == "another test"
+    assert model.attr2 == hash_string("TEST")
+    model.attr2 = "ANOTHER TEST"
+    assert model.attr2 == hash_string("ANOTHER TEST")