Add json_deserialize parameter to ClientSession

CHANGES/11741.feature.rst

@@ -0,0 +1,20 @@
+Added ``json_deserialize`` parameter to :class:`~aiohttp.ClientSession` to configure JSON deserialization at the session level, matching the existing ``json_serialize`` parameter -- by :user:`jtung`.
+
+This allows users to configure a custom JSON deserializer (e.g., ``orjson.loads``) once at session creation, and all calls to :meth:`~aiohttp.ClientResponse.json` will use it by default.
+
+Example usage:
+
+.. code-block:: python
+
+    import aiohttp
+    import orjson
+
+    session = aiohttp.ClientSession(
+        json_serialize=lambda obj: orjson.dumps(obj).decode(),
+        json_deserialize=orjson.loads
+    )
+
+    async with session.get(url) as response:
+        data = await response.json()  # Uses orjson.loads
+
+Additionally, fixed an inconsistency where ``json_serialize`` parameter defaulted to ``json.dumps`` directly instead of using ``DEFAULT_JSON_ENCODER`` constant, bringing it in line with other parts of the codebase.

aiohttp/client.py

@@ -4,7 +4,6 @@
 import base64
 import dataclasses
 import hashlib
-import json
 import os
 import sys
 import traceback
@@ -96,7 +95,15 @@
 from .http import WS_KEY, HttpVersion, WebSocketReader, WebSocketWriter
 from .http_websocket import WSHandshakeError, ws_ext_gen, ws_ext_parse
 from .tracing import Trace, TraceConfig
-from .typedefs import JSONEncoder, LooseCookies, LooseHeaders, StrOrURL
+from .typedefs import (
+    DEFAULT_JSON_DECODER,
+    DEFAULT_JSON_ENCODER,
+    JSONDecoder,
+    JSONEncoder,
+    LooseCookies,
+    LooseHeaders,
+    StrOrURL,
+)
 
 __all__ = (
     # client_exceptions
@@ -234,6 +241,7 @@ class ClientSession:
         "_default_auth",
         "_version",
         "_json_serialize",
+        "_json_deserialize",
         "_requote_redirect_url",
         "_timeout",
         "_raise_for_status",
@@ -266,7 +274,8 @@ def __init__(
         proxy_auth: BasicAuth | None = None,
         skip_auto_headers: Iterable[str] | None = None,
         auth: BasicAuth | None = None,
-        json_serialize: JSONEncoder = json.dumps,
+        json_serialize: JSONEncoder = DEFAULT_JSON_ENCODER,
+        json_deserialize: JSONDecoder = DEFAULT_JSON_DECODER,
         request_class: type[ClientRequest] = ClientRequest,
         response_class: type[ClientResponse] = ClientResponse,
         ws_response_class: type[ClientWebSocketResponse] = ClientWebSocketResponse,
@@ -344,6 +353,7 @@ def __init__(
         self._default_auth = auth
         self._version = version
         self._json_serialize = json_serialize
+        self._json_deserialize = json_deserialize
         self._raise_for_status = raise_for_status
         self._auto_decompress = auto_decompress
         self._trust_env = trust_env
@@ -1322,6 +1332,11 @@ def json_serialize(self) -> JSONEncoder:
         """Json serializer callable"""
         return self._json_serialize
 
+    @property
+    def json_deserialize(self) -> JSONDecoder:
+        """Json deserializer callable"""
+        return self._json_deserialize
+
     @property
     def connector_owner(self) -> bool:
         """Should connector be closed on session closing"""

aiohttp/client_reqrep.py

@@ -107,7 +107,6 @@ class _RequestInfo(NamedTuple):
 
 
 class RequestInfo(_RequestInfo):
-
     def __new__(
         cls,
         url: URL,
@@ -641,7 +640,7 @@ async def json(
         self,
         *,
         encoding: str | None = None,
-        loads: JSONDecoder = DEFAULT_JSON_DECODER,
+        loads: JSONDecoder | None = None,
         content_type: str | None = "application/json",
     ) -> Any:
         """Read and decodes JSON response."""
@@ -663,6 +662,14 @@ async def json(
         if encoding is None:
             encoding = self.get_encoding()
 
+        # Use session's deserializer if loads not explicitly provided
+        if loads is None:
+            loads = (
+                self._session.json_deserialize
+                if self._session is not None
+                else DEFAULT_JSON_DECODER
+            )
+
         return loads(self._body.decode(encoding))  # type: ignore[union-attr]
 
     async def __aenter__(self) -> "ClientResponse":

docs/spelling_wordlist.txt

@@ -97,6 +97,8 @@ cythonized
 de
 deduplicate
 defs
+deserialization
+deserializer
 Dependabot
 deprecations
 DER