fix: json serialisation (#1301)

Author: sansyrox

integration_tests/base_routes.py

@@ -376,6 +376,60 @@ async def async_json_get():
     return jsonify({"async json get": "json"})
 
 
+# JSON List (auto-serialized without explicit jsonify)
+
+
+@app.get("/sync/json/list")
+def sync_json_list_get():
+    return [
+        {"id": 1, "title": "First Post", "published": True},
+        {"id": 2, "title": "Draft Post", "published": False},
+        {"id": 3, "title": "Latest Post", "published": True},
+    ]
+
+
+@app.get("/async/json/list")
+async def async_json_list_get():
+    return [
+        {"id": 1, "title": "First Post", "published": True},
+        {"id": 2, "title": "Draft Post", "published": False},
+        {"id": 3, "title": "Latest Post", "published": True},
+    ]
+
+
+@app.get("/sync/json/list/empty")
+def sync_json_list_empty_get():
+    return []
+
+
+@app.get("/async/json/list/empty")
+async def async_json_list_empty_get():
+    return []
+
+
+@app.get("/sync/json/list/primitives")
+def sync_json_list_primitives_get():
+    return [1, 2, 3, "four", True, None]
+
+
+@app.get("/async/json/list/primitives")
+async def async_json_list_primitives_get():
+    return [1, 2, 3, "four", True, None]
+
+
+# JSON Dict (auto-serialized without explicit jsonify)
+
+
+@app.get("/sync/json/dict")
+def sync_json_dict_get():
+    return {"message": "sync dict", "count": 42, "active": True}
+
+
+@app.get("/async/json/dict")
+async def async_json_dict_get():
+    return {"message": "async dict", "count": 42, "active": True}
+
+
 @app.get("/sync/json/const", const=True)
 def sync_json_const_get():
     return jsonify({"sync json const get": "json"})

integration_tests/test_json_types.py

@@ -1,6 +1,6 @@
 import pytest
 
-from integration_tests.helpers.http_methods_helpers import json_post
+from integration_tests.helpers.http_methods_helpers import get, json_post
 
 
 @pytest.mark.parametrize("function_type", ["sync", "async"])
@@ -117,3 +117,65 @@ def test_json_mixed_types_preserved(function_type: str, session):
     assert result["field_name"]["type"] == "str"
     assert result["field_value"]["value"] == "111000111"
     assert result["field_value"]["type"] == "str"
+
+
+# ===== JSON List Serialization Tests (Issue #1300) =====
+
+
+@pytest.mark.parametrize("function_type", ["sync", "async"])
+def test_json_list_response_serialization(function_type: str, session):
+    """Test that returning a list from a handler is properly serialized as JSON"""
+    res = get(f"/{function_type}/json/list")
+
+    # Check content type is application/json
+    assert res.headers["content-type"] == "application/json"
+
+    # Check that response is valid JSON (not Python str representation)
+    result = res.json()
+    assert isinstance(result, list)
+    assert len(result) == 3
+
+    # Verify the data structure and types are correct
+    assert result[0] == {"id": 1, "title": "First Post", "published": True}
+    assert result[1] == {"id": 2, "title": "Draft Post", "published": False}
+    assert result[2] == {"id": 3, "title": "Latest Post", "published": True}
+
+    # Verify booleans are proper JSON booleans (true/false), not Python (True/False)
+    # This is implicitly tested by res.json() succeeding, but let's verify the raw response too
+    assert "true" in res.text.lower()
+    assert "false" in res.text.lower()
+    assert "True" not in res.text  # Python boolean should not appear
+    assert "False" not in res.text
+
+
+@pytest.mark.parametrize("function_type", ["sync", "async"])
+def test_json_empty_list_response_serialization(function_type: str, session):
+    """Test that returning an empty list is properly serialized as JSON"""
+    res = get(f"/{function_type}/json/list/empty")
+
+    assert res.headers["content-type"] == "application/json"
+    result = res.json()
+    assert result == []
+    assert res.text == "[]"
+
+
+@pytest.mark.parametrize("function_type", ["sync", "async"])
+def test_json_list_primitives_response_serialization(function_type: str, session):
+    """Test that a list of primitives is properly serialized as JSON"""
+    res = get(f"/{function_type}/json/list/primitives")
+
+    assert res.headers["content-type"] == "application/json"
+    result = res.json()
+    assert result == [1, 2, 3, "four", True, None]
+
+
+@pytest.mark.parametrize("function_type", ["sync", "async"])
+def test_json_dict_response_auto_serialization(function_type: str, session):
+    """Test that returning a dict from a handler is properly auto-serialized as JSON"""
+    res = get(f"/{function_type}/json/dict")
+
+    assert res.headers["content-type"] == "application/json"
+    result = res.json()
+    assert result["message"] == f"{function_type} dict"
+    assert result["count"] == 42
+    assert result["active"] is True

robyn/jsonify.py

@@ -1,13 +1,15 @@
+from typing import Any, Dict, List, Union
+
 import orjson
 
 
-def jsonify(input_dict: dict) -> str:
+def jsonify(data: Union[Dict[str, Any], List[Any]]) -> str:
     """
-    This function serializes input dict to a json string
+    This function serializes input data to a json string
 
     Attributes:
-        input_dict dict: response of the function
+        data: dict or list to serialize as JSON response
     """
-    output_binary = orjson.dumps(input_dict)
+    output_binary = orjson.dumps(data)
     output_str = output_binary.decode("utf-8")
     return output_str

robyn/router.py

@@ -72,15 +72,15 @@ def _format_tuple_response(self, res: tuple) -> Response:
 
     def _format_response(
         self,
-        res: Union[Dict, Response, StreamingResponse, bytes, tuple, str],
+        res: Union[Dict, List, Response, StreamingResponse, bytes, tuple, str],
     ) -> Union[Response, StreamingResponse]:
         if isinstance(res, Response):
             return res
 
         if isinstance(res, StreamingResponse):
             return res
 
-        if isinstance(res, dict):
+        if isinstance(res, (dict, list)):
             return Response(
                 status_code=status_codes.HTTP_200_OK,
                 headers=Headers({"Content-Type": "application/json"}),