Merge pull request #132 from mjpieters/cache_pydantic_fields

Cache pydantic model fields for faster decoding

fastapi_cache/coder.py

@@ -3,7 +3,7 @@ import datetime
 import json
 import pickle  # nosec:B403
 from decimal import Decimal
-from typing import Any, Callable, TypeVar, overload
+from typing import Any, Callable, ClassVar, Dict, TypeVar, overload
 
 import pendulum
 from fastapi.encoders import jsonable_encoder
@@ -53,6 +53,13 @@ class Coder:
     def decode(cls, value: str) -> Any:
         raise NotImplementedError
 
+    # (Shared) cache for endpoint return types to Pydantic model fields.
+    # Note that subclasses share this cache! If a subclass overrides the
+    # decode_as_type method and then stores a different kind of field for a
+    # given type, do make sure that the subclass provides its own class
+    # attribute for this cache.
+    _type_field_cache: ClassVar[Dict[Any, fields.ModelField]] = {}
+
     @overload
     @classmethod
     def decode_as_type(cls, value: str, type_: _T) -> _T:
@@ -72,9 +79,12 @@ class Coder:
         """
         result = cls.decode(value)
         if type_ is not None:
-            field = fields.ModelField(
+            try:
-                name="body", type_=type_, class_validators=None, model_config=BaseConfig
+                field = cls._type_field_cache[type_]
-            )
+            except KeyError:
+                field = cls._type_field_cache[type_] = fields.ModelField(
+                    name="body", type_=type_, class_validators=None, model_config=BaseConfig
+                )
             result, errors = field.validate(result, {}, loc=())
             if errors is not None:
                 if not isinstance(errors, list):