fix: validate empty resources for non-suffix responders

docs/_newsfragments/2167.bugfix.rst

@@ -0,0 +1,3 @@
+Resources without responder methods now emit a ``UserWarning`` for non-suffix responders.
+Resources must define at least one responder method (e.g., ``on_get()``, ``on_post()``).
+This will raise an error in Falcon 5.0.

falcon/routing/util.py

@@ -17,6 +17,7 @@
 from __future__ import annotations
 
 from typing import TYPE_CHECKING
+import warnings
 
 from falcon import constants
 from falcon import responders
@@ -69,11 +70,19 @@ def map_http_methods(resource: object, suffix: str | None = None) -> MethodDict:
             if callable(responder):
                 method_map[method] = responder
 
-    # If suffix is specified and doesn't map to any methods, raise an error
-    if suffix and not method_map:
-        raise SuffixedMethodNotFoundError(
-            'No responders found for the specified suffix'
-        )
+    # If doesn't map to any methods, raise an error
+    if not method_map:
+        resource_name = resource.__class__.__name__
+        if suffix:
+            raise SuffixedMethodNotFoundError(
+                f'No responders found for the specified resource: '
+                f'{resource_name} and suffix: {suffix}'
+            )
+        else:
+            warnings.warn(
+                'No responders (on_get, on_post, etc.) '
+                + f'found for the specified resource: {resource_name}'
+            )
 
     return method_map
 

tests/asgi/test_ws.py

@@ -1087,7 +1087,8 @@ async def on_websocket(self, req, ws):
 
 async def test_ws_simulator_collect_edge_cases(conductor):
     class Resource:
-        pass
+        async def on_websocket(self, req, ws):
+            pass
 
     conductor.app.add_route('/', Resource())
 

tests/test_http_method_routing.py

@@ -40,11 +40,6 @@
 ]
 
 
-@pytest.fixture
-def stonewall():
-    return Stonewall()
-
-
 @pytest.fixture
 def resource_things():
     return ThingsResource()
@@ -64,8 +59,6 @@ def resource_get_with_faulty_put():
 def client(asgi, util):
     app = util.create_app(asgi)
 
-    app.add_route('/stonewall', Stonewall())
-
     resource_things = ThingsResource()
     app.add_route('/things', resource_things)
     app.add_route('/things/{id}/stuff/{sid}', resource_things)
@@ -115,10 +108,6 @@ def on_websocket(self, req, resp, id, sid):
         self.called = True
 
 
-class Stonewall:
-    pass
-
-
 def capture(func):
     @wraps(func)
     def with_capture(*args, **kwargs):
@@ -238,12 +227,6 @@ def test_misc(self, client, resource_misc, catch_wsgiref_query_warning):
             assert resource_misc.called
             assert resource_misc.req.method == method
 
-    def test_methods_not_allowed_simple(self, client, stonewall):
-        client.app.add_route('/stonewall', stonewall)
-        for method in ['GET', 'HEAD', 'PUT', 'PATCH']:
-            response = client.simulate_request(path='/stonewall', method=method)
-            assert response.status == falcon.HTTP_405
-
     def test_methods_not_allowed_complex(
         self, client, resource_things, catch_wsgiref_query_warning
     ):

tests/test_uri_templates.py

@@ -602,3 +602,11 @@ def test_custom_error_on_suffix_route_not_found(client):
             resource_with_suffix_routes,
             suffix='bad-alt',
         )
+
+
+def test_custom_error_route_not_found(client):
+    class EmptyResource:
+        pass
+
+    with pytest.warns(UserWarning):
+        client.app.add_route('/empty', EmptyResource())