Adds extended JSONEncoder that can serialize pydantic models.

rath/json/encoders.py

@@ -0,0 +1,31 @@
+import json
+from datetime import datetime
+from json import JSONEncoder
+from typing import Any
+
+from pydantic import BaseModel
+
+
+class PydanticJsonEncoder(JSONEncoder):
+    """
+    A JSONEncoder that can serialize pydantic models.
+    """
+    def default(self, o: Any) -> Any:
+        if isinstance(o, BaseModel):
+            return o.dict(by_alias=True)
+        if isinstance(o, datetime):
+            return o.isoformat("T")
+        return super().default(o)
+
+
+def dumps(value: Any):
+    """
+    Serialize an object to a JSON formatted string using PydanticJsonEncoder.
+
+    Arguments:
+        value (Any): The object to serialize.
+
+    Returns:
+        str: The serialized string.
+    """
+    return json.dumps(value, cls=PydanticJsonEncoder)

rath/links/aiohttp.py

@@ -3,7 +3,9 @@
 from typing import Any, Dict, List
 
 import aiohttp
+from aiohttp.typedefs import JSONEncoder
 from graphql import OperationType
+from rath.json.encoders import dumps
 from pydantic import Field
 from rath.operation import GraphQLException, GraphQLResult, Operation
 from rath.links.base import AsyncTerminatingLink
@@ -20,9 +22,12 @@ class AIOHttpLink(AsyncTerminatingLink):
     )
 
     _session = None
+    _json_encoder: JSONEncoder = dumps
 
     async def __aenter__(self) -> None:
-        self._session = await aiohttp.ClientSession().__aenter__()
+        self._session = await aiohttp.ClientSession(
+            json_serialize=self._json_encoder
+        ).__aenter__()
 
     async def __aexit__(self, *args, **kwargs) -> None:
         await self._session.__aexit__(*args, **kwargs)

tests/test_json.py

@@ -0,0 +1,51 @@
+from datetime import datetime
+from typing import Dict
+
+import pytest
+from pydantic import BaseModel, Field
+
+from rath.json.encoders import dumps
+
+
+class TestInput(BaseModel):
+    start_time: datetime = Field(alias="startTime")
+    some_dict: Dict[str, float] = Field(alias="someDict")
+
+
+@pytest.fixture
+def example_input():
+    return TestInput(
+        startTime=datetime.utcnow(),
+        someDict={
+            "a": 1.0,
+            "b": 2.0,
+        },
+    )
+
+
+def test_json_dumps(example_input):
+    """
+    Tests that extended json dumps() method does not throw exception when
+    serializing a pydantic model
+    :param example_input: Example pydantic model.
+    """
+    dumps(example_input)
+
+
+def test_json_dumps_throws_for_unknown_type():
+    """
+    Tests that extended json dumps() method still raises TypeError for unknown type
+    """
+    with pytest.raises(TypeError):
+        dumps(bytes([0x01, 0x02, 0x03, 0x04, 0x05, 0x06]))
+
+
+def test_json_roundtrip(example_input):
+    """
+    Tests that extended json dumps() method produces output
+    that matches input on a round trip
+    :param example_input: Example pydantic model.
+    """
+    json_string = dumps(example_input)
+    round_trip = TestInput.parse_raw(json_string)
+    assert example_input == round_trip