Changes:

- fix `data` and `payload` special keyword arguments so they are allowed
  when another method than one without a body (HEAD, GET) is available,

docs/en/docs/release-notes.md

@@ -26,6 +26,7 @@ hide:
 
 ### Fixed
 
+- `data` and `payload` special kwargs are now allowed when a not-bodyless method is available for the handler. They default to None.
 - `bytes` won't be encoded as json when returned from a handler. This would unexpectly lead to a base64 encoding.
 
 ## 3.6.1

esmerald/routing/router.py

@@ -1917,6 +1917,9 @@ def wrapper(func: Callable) -> Callable:
         return wrapper
 
 
+_body_less_methods = frozenset({"GET", "HEAD"})
+
+
 class HTTPHandler(Dispatcher, OpenAPIFieldInfoMixin, LilyaPath):
     __slots__ = (
         "path",
@@ -2222,12 +2225,18 @@ def validate_reserved_kwargs(self) -> None:  # pragma: no cover
         """
         Validates if special words are in the signature.
         """
-        if DATA in self.handler_signature.parameters and "GET" in self.methods:
-            raise ImproperlyConfigured("'data' argument is unsupported for 'GET' request handlers")
+        if DATA in self.handler_signature.parameters and _body_less_methods.issuperset(
+            self.methods
+        ):
+            raise ImproperlyConfigured(
+                "'data' argument is unsupported for 'GET' and 'HEAD' request handlers"
+            )
 
-        if PAYLOAD in self.handler_signature.parameters and "GET" in self.methods:
+        if PAYLOAD in self.handler_signature.parameters and _body_less_methods.issuperset(
+            self.methods
+        ):
             raise ImproperlyConfigured(
-                "'payload' argument is unsupported for 'GET' request handlers"
+                "'payload' argument is unsupported for 'GET' and 'HEAD' request handlers"
             )
 
         if SOCKET in self.handler_signature.parameters:

tests/forms/test_forms_route.py

@@ -0,0 +1,24 @@
+from pydantic import BaseModel
+
+from esmerald import Esmerald, Form, Request
+from esmerald.routing.gateways import Gateway
+from esmerald.routing.handlers import route
+from esmerald.testclient import EsmeraldTestClient
+
+
+class Model(BaseModel):
+    id: str
+
+
+def test_get_and_post():
+    @route(methods=["GET", "POST"])
+    async def start(request: Request, form: Model | None = Form()) -> bytes:
+        return b"hello world"
+
+    app = Esmerald(
+        debug=True,
+        routes=[Gateway("/", handler=start)],
+    )
+    client = EsmeraldTestClient(app)
+    response = client.get("/")
+    assert response.status_code == 200

tests/routing/test_routing.py

@@ -1,6 +1,7 @@
 import contextlib
 import uuid
 from dataclasses import dataclass
+from typing import Optional
 
 import pytest
 from lilya.responses import JSONResponse, PlainText, Response as LilyaResponse
@@ -10,13 +11,14 @@
 
 from esmerald.applications import Esmerald
 from esmerald.enums import MediaType
+from esmerald.exceptions import ImproperlyConfigured
 from esmerald.permissions import AllowAny, DenyAll
 from esmerald.requests import Request
 from esmerald.responses import Response
 from esmerald.responses.encoders import UJSONResponse
 from esmerald.routing.apis.views import APIView
 from esmerald.routing.gateways import Gateway, WebSocketGateway
-from esmerald.routing.handlers import get, post, put, websocket
+from esmerald.routing.handlers import get, post, put, route, websocket
 from esmerald.routing.router import Include, Router
 from esmerald.testclient import create_client
 
@@ -1020,3 +1022,54 @@ def another_user(data: UserOut) -> UserOut:
 
     assert response.status_code == 200
     assert response.json() == {"name": "test", "email": "[email protected]"}
+
+
+def test_get_and_post_data(test_app_client_factory):
+    @route(path="/another-user", status_code=200, methods=["GET", "POST"])
+    def another_user(data: Optional[UserOut]) -> Optional[UserOut]:
+        return data
+
+    data = {"name": "test", "email": "[email protected]"}
+    app = Esmerald(routes=[Gateway(handler=another_user)])
+    client = test_app_client_factory(app)
+    response = client.get("/another-user")
+    assert response.status_code == 200
+    assert response.text == ""
+    response = client.post("/another-user", json=data)
+
+    assert response.status_code == 200
+    assert response.json() == {"name": "test", "email": "[email protected]"}
+
+
+def test_get_and_post_payload(test_app_client_factory):
+    @route(path="/another-user", status_code=200, methods=["GET", "POST"])
+    def another_user(payload: Optional[UserOut]) -> Optional[UserOut]:
+        return payload
+
+    data = {"name": "test", "email": "[email protected]"}
+    app = Esmerald(routes=[Gateway(handler=another_user)])
+
+    client = test_app_client_factory(app)
+    response = client.get("/another-user")
+    assert response.status_code == 200
+    assert response.text == ""
+    response = client.post("/another-user", json=data)
+
+    assert response.status_code == 200
+    assert response.json() == {"name": "test", "email": "[email protected]"}
+
+
+def test_get_and_head_data():
+    with pytest.raises(ImproperlyConfigured):
+
+        @route(path="/another-user", status_code=200, methods=["GET", "HEAD"])
+        def another_user(data: UserOut) -> UserOut:
+            return data
+
+
+def test_get_and_head_payload():
+    with pytest.raises(ImproperlyConfigured):
+
+        @route(path="/another-user", status_code=200, methods=["GET", "HEAD"])
+        def another_user(payload: UserOut) -> UserOut:
+            return payload