- Replaced json.dumps/json.loads with pydantic_core to_json/from_json

- `_serialize_response`: model list mapping now handled by Pydantic instead of manual recursion

Author: mr-fatalyst

CHANGELOG.md

@@ -6,11 +6,15 @@ FastOpenAPI follows the [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ## [0.7.0] - Unreleased
 
+### Changed
+- Replaced `json.dumps/json.loads` with pydantic_core `to_json/from_json`
+- `_serialize_response`: model list mapping now handled by Pydantic instead of manual recursion
+
 ### Fixed
-- Fixed issue with parsing repeated query parameters in URL.
+- Issue with parsing repeated query parameters in URL.
 
 ### Removed
-- Removed the `use_aliases` from `BaseRouter` and reverted changes from 0.6.0.
+- The `use_aliases` from `BaseRouter` and reverted changes from 0.6.0.
 
 ## [0.6.0] – 2025‑04‑16
 

fastopenapi/base_router.py

@@ -405,6 +405,8 @@ def _register_docs_endpoints(self):
     def _serialize_response(cls, result: Any) -> Any:
         if isinstance(result, BaseModel):
             return result.model_dump(by_alias=True)
+        if isinstance(result, list) and result and isinstance(result[0], BaseModel):
+            return [item.model_dump(by_alias=True) for item in result]
         if isinstance(result, list):
             return [cls._serialize_response(item) for item in result]
         if isinstance(result, dict):

fastopenapi/routers/falcon.py

@@ -1,9 +1,9 @@
 import inspect
-import json
 from collections.abc import Callable
 from http import HTTPStatus
 
 import falcon.asgi
+from pydantic_core import from_json
 
 from fastopenapi.base_router import BaseRouter
 
@@ -110,7 +110,7 @@ async def _read_body(self, req):
         try:
             body_bytes = await req.bounded_stream.read()
             if body_bytes:
-                return json.loads(body_bytes.decode("utf-8"))
+                return from_json(body_bytes.decode("utf-8"))
         except Exception:
             pass
         return {}

fastopenapi/routers/starlette.py

@@ -1,8 +1,8 @@
 import functools
 import inspect
-import json
 from collections.abc import Callable
 
+from pydantic_core import from_json
 from starlette.applications import Starlette
 from starlette.responses import HTMLResponse, JSONResponse
 from starlette.routing import Route
@@ -25,7 +25,7 @@ async def _starlette_view(cls, request, router, endpoint):
         try:
             body_bytes = await request.body()
             if body_bytes:
-                body = json.loads(body_bytes.decode("utf-8"))
+                body = from_json(body_bytes.decode("utf-8"))
         except Exception:
             pass
         all_params = {**query_params, **request.path_params}

fastopenapi/routers/tornado.py

@@ -2,12 +2,16 @@
 import re
 from collections.abc import Callable
 
-from tornado.escape import json_decode, json_encode
+from pydantic_core import from_json, to_json
 from tornado.web import Application, RequestHandler, url
 
 from fastopenapi.base_router import BaseRouter
 
 
+def json_encode(data):
+    return to_json(data).decode("utf-8").replace("</", "<\\/")
+
+
 class TornadoDynamicHandler(RequestHandler):
     """
     A dynamic request handler for Tornado, which resolves endpoint parameters and
@@ -26,7 +30,7 @@ def initialize(self, **kwargs):
     async def prepare(self):
         if self.request.body:
             try:
-                self.json_body = json_decode(self.request.body)
+                self.json_body = from_json(self.request.body)
             except Exception:
                 self.json_body = {}
         else:

tests/aiohttp/test_aiohttp_integration.py

@@ -1,6 +1,5 @@
-import json
-
 import pytest
+from pydantic_core import to_json
 
 
 class TestAioHttpIntegration:
@@ -61,7 +60,9 @@ async def test_create_item(self, client):
         """Test creating an item"""
         new_item = {"name": "New Item", "description": "New Description"}
         headers = {"Content-Type": "application/json"}
-        resp = await client.post("/items", data=json.dumps(new_item), headers=headers)
+        resp = await client.post(
+            "/items", data=to_json(new_item).decode("utf-8"), headers=headers
+        )
         assert resp.status == 201
         data = await resp.json()
         assert data["id"] == 3
@@ -73,7 +74,9 @@ async def test_create_item_incorrect(self, client):
         """Test creating an item with invalid data"""
         new_item = {"name": None, "description": "New Description"}
         headers = {"Content-Type": "application/json"}
-        resp = await client.post("/items", data=json.dumps(new_item), headers=headers)
+        resp = await client.post(
+            "/items", data=to_json(new_item).decode("utf-8"), headers=headers
+        )
         assert resp.status == 422
         data = await resp.json()
         assert "Validation error for parameter" in data["error"]["message"]
@@ -93,7 +96,7 @@ async def test_update_item(self, client):
         update_data = {"name": "Updated Item", "description": "Updated Description"}
         headers = {"Content-Type": "application/json"}
         resp = await client.put(
-            "/items/2", data=json.dumps(update_data), headers=headers
+            "/items/2", data=to_json(update_data).decode("utf-8"), headers=headers
         )
         assert resp.status == 200
         data = await resp.json()

tests/falcon/test_falcon_integration.py

@@ -1,6 +1,5 @@
-import json
-
 import pytest
+from pydantic_core import from_json, to_json
 
 
 class TestFalconIntegration:
@@ -10,7 +9,7 @@ def test_get_items_sync(self, sync_client):
         response = sync_client.simulate_get("/items-sync")
 
         assert response.status_code == 200
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert len(result) == 2
         assert result[0]["name"] == "Item 1"
         assert result[1]["name"] == "Item 2"
@@ -21,7 +20,7 @@ async def test_get_items(self, async_client):
         response = await async_client.simulate_get("/items")
 
         assert response.status_code == 200
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert len(result) == 2
         assert result[0]["name"] == "Item 1"
         assert result[1]["name"] == "Item 2"
@@ -32,7 +31,7 @@ async def test_get_items_fail(self, async_client):
         response = await async_client.simulate_get("/items-fail")
 
         assert response.status_code == 500
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert result["error"]["message"] == "TEST ERROR"
 
     @pytest.mark.asyncio
@@ -41,7 +40,7 @@ async def test_get_item(self, async_client):
         response = await async_client.simulate_get("/items/1")
 
         assert response.status_code == 200
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert result["id"] == 1
         assert result["name"] == "Item 1"
         assert result["description"] == "Description 1"
@@ -52,7 +51,7 @@ async def test_get_item_bad_request(self, async_client):
         response = await async_client.simulate_get("/items/abc")
 
         assert response.status_code == 400
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert result["error"]["message"] == (
             "Error parsing parameter 'item_id'. Must be a valid int"
         )
@@ -70,12 +69,12 @@ async def test_create_item(self, async_client):
         new_item = {"name": "New Item", "description": "New Description"}
         response = await async_client.simulate_post(
             "/items",
-            body=json.dumps(new_item),
+            body=to_json(new_item).decode("utf-8"),
             headers={"Content-Type": "application/json"},
         )
 
         assert response.status_code == 201
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert result["id"] == 3
         assert result["name"] == "New Item"
         assert result["description"] == "New Description"
@@ -86,12 +85,12 @@ async def test_create_item_incorrect(self, async_client):
         new_item = {"name": None, "description": "New Description"}
         response = await async_client.simulate_post(
             "/items",
-            body=json.dumps(new_item),
+            body=to_json(new_item).decode("utf-8"),
             headers={"Content-Type": "application/json"},
         )
 
         assert response.status_code == 422
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert "Validation error for parameter" in result["error"]["message"]
 
     @pytest.mark.asyncio
@@ -104,7 +103,7 @@ async def test_create_item_invalid_json(self, async_client):
         )
 
         assert response.status_code == 422
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert "Validation error for parameter" in result["error"]["message"]
 
     @pytest.mark.asyncio
@@ -113,12 +112,12 @@ async def test_update_item(self, async_client):
         update_data = {"name": "Updated Item", "description": "Updated Description"}
         response = await async_client.simulate_put(
             "/items/2",
-            body=json.dumps(update_data),
+            body=to_json(update_data).decode("utf-8"),
             headers={"Content-Type": "application/json"},
         )
 
         assert response.status_code == 200
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert result["id"] == 2
         assert result["name"] == "Updated Item"
         assert result["description"] == "Updated Description"
@@ -140,7 +139,7 @@ async def test_openapi_schema_endpoint(self, async_client):
         response = await async_client.simulate_get("/openapi.json")
 
         assert response.status_code == 200
-        schema = json.loads(response.text)
+        schema = from_json(response.text)
         assert schema["info"]["title"] == "Test API"
         assert "/items" in schema["paths"]
         assert "/items/{item_id}" in schema["paths"]
@@ -169,15 +168,15 @@ async def test_query_parameters_handling(self, async_client):
         # Test with a single value parameter
         response = await async_client.get("/list-test?param1=single_value")
         assert response.status_code == 200
-        data = json.loads(response.text)
+        data = from_json(response.text)
         assert data["received_param1"] == "single_value"
 
         # Test with a parameter that has multiple values
         response = await async_client.get(
             "/list-test?param1=first_value&param2=value1&param2=value2"
         )
         assert response.status_code == 200
-        data = json.loads(response.text)
+        data = from_json(response.text)
         assert data["received_param1"] == "first_value"
         assert isinstance(data["received_param2"], list)
         assert data["received_param2"] == ["value1", "value2"]

tests/flask/test_flask_integration.py

@@ -1,4 +1,4 @@
-import json
+from pydantic_core import from_json, to_json
 
 
 class TestFlaskIntegration:
@@ -8,7 +8,7 @@ def test_get_items(self, client):
         response = client.get("/items")
 
         assert response.status_code == 200
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert len(result) == 2
         assert result[0]["name"] == "Item 1"
         assert result[1]["name"] == "Item 2"
@@ -18,15 +18,15 @@ def test_get_items_fail(self, client):
         response = client.get("/items-fail")
 
         assert response.status_code == 500
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert result["error"]["message"] == "TEST ERROR"
 
     def test_get_item(self, client):
         """Test fetching an item by ID"""
         response = client.get("/items/1")
 
         assert response.status_code == 200
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert result["id"] == 1
         assert result["name"] == "Item 1"
         assert result["description"] == "Description 1"
@@ -36,7 +36,7 @@ def test_get_item_bad_request(self, client):
         response = client.get("/items/abc")
 
         assert response.status_code == 400
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert result["error"]["message"] == (
             "Error parsing parameter 'item_id'. Must be a valid int"
         )
@@ -52,12 +52,12 @@ def test_create_item(self, client):
         new_item = {"name": "New Item", "description": "New Description"}
         response = client.post(
             "/items",
-            data=json.dumps(new_item),
+            data=to_json(new_item).decode("utf-8"),
             headers={"Content-Type": "application/json"},
         )
 
         assert response.status_code == 201
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert result["id"] == 3
         assert result["name"] == "New Item"
         assert result["description"] == "New Description"
@@ -67,12 +67,12 @@ def test_create_item_incorrect(self, client):
         new_item = {"name": None, "description": "New Description"}
         response = client.post(
             "/items",
-            data=json.dumps(new_item),
+            data=to_json(new_item).decode("utf-8"),
             headers={"Content-Type": "application/json"},
         )
 
         assert response.status_code == 422
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert "Validation error for parameter" in result["error"]["message"]
 
     def test_create_item_invalid_json(self, client):
@@ -84,20 +84,20 @@ def test_create_item_invalid_json(self, client):
         )
 
         assert response.status_code == 422
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert "Validation error for parameter" in result["error"]["message"]
 
     def test_update_item(self, client):
         """Test updating an item"""
         update_data = {"name": "Updated Item", "description": "Updated Description"}
         response = client.put(
             "/items/2",
-            data=json.dumps(update_data),
+            data=to_json(update_data).decode("utf-8"),
             headers={"Content-Type": "application/json"},
         )
 
         assert response.status_code == 200
-        result = json.loads(response.text)
+        result = from_json(response.text)
         assert result["id"] == 2
         assert result["name"] == "Updated Item"
         assert result["description"] == "Updated Description"
@@ -117,7 +117,7 @@ def test_openapi_schema_endpoint(self, client):
         response = client.get("/openapi.json")
 
         assert response.status_code == 200
-        schema = json.loads(response.text)
+        schema = from_json(response.text)
         assert schema["info"]["title"] == "Test API"
         assert "/items" in schema["paths"]
         assert "/items/{item_id}" in schema["paths"]