Make BaseSerializer abstract (#624)

Author: Dreamsorcerer

aiocache/serializers/serializers.py

@@ -1,5 +1,6 @@
 import logging
 import pickle  # noqa: S403
+from abc import ABC, abstractmethod
 from typing import Any, Optional
 
 logger = logging.getLogger(__name__)
@@ -20,7 +21,7 @@
 _NOT_SET = object()
 
 
-class BaseSerializer:
+class BaseSerializer(ABC):
 
     DEFAULT_ENCODING: Optional[str] = "utf-8"
 
@@ -29,12 +30,14 @@ def __init__(self, *args, encoding=_NOT_SET, **kwargs):
         super().__init__(*args, **kwargs)
 
     # TODO(PY38): Positional-only
-    def dumps(self, value: Any) -> str:
-        raise NotImplementedError("dumps method must be implemented")
+    @abstractmethod
+    def dumps(self, value: Any) -> Any:
+        """Serialise the value to be stored in the backend."""
 
     # TODO(PY38): Positional-only
-    def loads(self, value: str) -> Any:
-        raise NotImplementedError("loads method must be implemented")
+    @abstractmethod
+    def loads(self, value: Any) -> Any:
+        """Decode the value retrieved from the backend."""
 
 
 class NullSerializer(BaseSerializer):

examples/marshmallow_serializer_class.py

@@ -1,6 +1,7 @@
 import random
 import string
 import asyncio
+from typing import Any
 
 from marshmallow import fields, Schema, post_load
 
@@ -21,16 +22,12 @@ def __eq__(self, obj):
         return self.__dict__ == obj.__dict__
 
 
-class MarshmallowSerializer(Schema, BaseSerializer):  # type: ignore[misc]
+class RandomSchema(Schema):
     int_type = fields.Integer()
     str_type = fields.String()
     dict_type = fields.Dict()
     list_type = fields.List(fields.Integer())
 
-    # marshmallow Schema class doesn't play nicely with multiple inheritance and won't call
-    # BaseSerializer.__init__
-    encoding = 'utf-8'
-
     @post_load
     def build_my_type(self, data, **kwargs):
         return RandomModel(**data)
@@ -39,6 +36,18 @@ class Meta:
         strict = True
 
 
+class MarshmallowSerializer(BaseSerializer):
+    def __init__(self, *args: Any, **kwargs: Any):
+        super().__init__(*args, **kwargs)
+        self.schema = RandomSchema()
+
+    def dumps(self, value: Any) -> str:
+        return self.schema.dumps(value)
+
+    def loads(self, value: str) -> Any:
+        return self.schema.loads(value)
+
+
 cache = Cache(serializer=MarshmallowSerializer(), namespace="main")
 
 

tests/acceptance/test_serializers.py

@@ -1,5 +1,6 @@
 import pickle
 import random
+from typing import Any
 
 import pytest
 from marshmallow import Schema, fields, post_load
@@ -29,15 +30,8 @@ def __eq__(self, obj):
         return self.__dict__ == obj.__dict__
 
 
-class MyTypeSchema(Schema, BaseSerializer):
+class MySchema(Schema):
     r = fields.Integer()
-    encoding = "utf-8"
-
-    def dumps(self, *args, **kwargs):
-        return super().dumps(*args, **kwargs)
-
-    def loads(self, *args, **kwargs):
-        return super().loads(*args, **kwargs)
 
     @post_load
     def build_my_type(self, data, **kwargs):
@@ -47,6 +41,18 @@ class Meta:
         strict = True
 
 
+class MyTypeSchema(BaseSerializer):
+    def __init__(self, *args: Any, **kwargs: Any):
+        super().__init__(*args, **kwargs)
+        self.schema = MySchema()
+
+    def dumps(self, value: Any) -> str:
+        return self.schema.dumps(value)
+
+    def loads(self, value: str) -> Any:
+        return self.schema.loads(value)
+
+
 class TestNullSerializer:
     TYPES = (1, 2.0, "hi", True, ["1", 1], {"key": "value"}, MyType())
 

tests/ut/test_serializers.py

@@ -20,33 +20,18 @@
 JSON_TYPES = [1, 2.0, "hi", True, ["1", 1], {"key": "value"}]
 
 
-class TestBaseSerializer:
+class TestNullSerializer:
     def test_init(self):
-        serializer = BaseSerializer()
+        serializer = NullSerializer()
+        assert isinstance(serializer, BaseSerializer)
         assert serializer.DEFAULT_ENCODING == "utf-8"
         assert serializer.encoding == "utf-8"
 
     def test_init_encoding(self):
-        serializer = BaseSerializer(encoding="whatever")
+        serializer = NullSerializer(encoding="whatever")
         assert serializer.DEFAULT_ENCODING == "utf-8"
         assert serializer.encoding == "whatever"
 
-    def test_dumps(self):
-        with pytest.raises(NotImplementedError):
-            BaseSerializer().dumps("")
-
-    def test_loads(self):
-        with pytest.raises(NotImplementedError):
-            BaseSerializer().loads("")
-
-
-class TestNullSerializer:
-    def test_init(self):
-        serializer = NullSerializer()
-        assert isinstance(serializer, BaseSerializer)
-        assert serializer.DEFAULT_ENCODING == "utf-8"
-        assert serializer.encoding == "utf-8"
-
     @pytest.mark.parametrize("obj", TYPES)
     def test_set_types(self, obj):
         assert NullSerializer().dumps(obj) is obj