fix(WebSocket): properly handle HTTPStatus and HTTPError cases (#2150)

* fix(websocket): properly handle HTTPStatus and HTTPError cases when using websockets

* test: fix failing tests

* test: add missing test coverage

* docs: add newsfragment

* chore: explicit raise for unsupported call of internal methods

* style: fix imports

* docs(towncrier): improve the bugfix newsfragment

---------

Co-authored-by: Vytautas Liuolia <vytautas.liuolia@gmail.com>

docs/_newsfragments/2146.bugfix.rst

@@ -0,0 +1,6 @@
+
+:ref:`WebSocket <ws>` implementation has been fixed to properly handle
+:class:`~falcon.HTTPError` and :class:`~falcon.HTTPStatus` exceptions raised by
+custom :func:`error handlers <falcon.asgi.App.add_error_handler>`.
+The WebSocket connection is now correctly closed with an appropriate code
+instead of bubbling up an unhandled error to the application server.

falcon/asgi/app.py

@@ -44,6 +44,7 @@
 from .request import Request
 from .response import Response
 from .structures import SSEvent
+from .ws import http_status_to_ws_code
 from .ws import WebSocket
 from .ws import WebSocketOptions
 
@@ -1025,30 +1026,45 @@ def _prepare_middleware(self, middleware=None, independent_middleware=False):
             asgi=True,
         )
 
-    async def _http_status_handler(self, req, resp, status, params):
-        self._compose_status_response(req, resp, status)
+    async def _http_status_handler(self, req, resp, status, params, ws=None):
+        if resp:
+            self._compose_status_response(req, resp, status)
+        elif ws:
+            code = http_status_to_ws_code(status.status)
+            falcon._logger.error(
+                '[FALCON] HTTPStatus %s raised while handling WebSocket. '
+                'Closing with code %s',
+                status,
+                code,
+            )
+            await ws.close(code)
+        else:
+            raise NotImplementedError('resp or ws expected')
 
     async def _http_error_handler(self, req, resp, error, params, ws=None):
         if resp:
             self._compose_error_response(req, resp, error)
-
-        if ws:
+        elif ws:
+            code = http_status_to_ws_code(error.status_code)
             falcon._logger.error(
-                '[FALCON] WebSocket handshake rejected due to raised HTTP error: %s',
+                '[FALCON] HTTPError %s raised while handling WebSocket. '
+                'Closing with code %s',
                 error,
+                code,
             )
-
-            code = 3000 + error.status_code
             await ws.close(code)
+        else:
+            raise NotImplementedError('resp or ws expected')
 
     async def _python_error_handler(self, req, resp, error, params, ws=None):
         falcon._logger.error('[FALCON] Unhandled exception in ASGI app', exc_info=error)
 
         if resp:
             self._compose_error_response(req, resp, falcon.HTTPInternalServerError())
-
-        if ws:
+        elif ws:
             await self._ws_cleanup_on_error(ws)
+        else:
+            raise NotImplementedError('resp or ws expected')
 
     async def _ws_disconnected_error_handler(self, req, resp, error, params, ws):
         falcon._logger.debug(
@@ -1093,9 +1109,9 @@ async def _handle_exception(self, req, resp, ex, params, ws=None):
                 await err_handler(req, resp, ex, params, **kwargs)
 
             except HTTPStatus as status:
-                self._compose_status_response(req, resp, status)
+                await self._http_status_handler(req, resp, status, params, ws=ws)
             except HTTPError as error:
-                self._compose_error_response(req, resp, error)
+                await self._http_error_handler(req, resp, error, params, ws=ws)
 
             return True
 

falcon/asgi/ws.py

@@ -701,3 +701,8 @@ async def _pump(self):
             if self._pop_message_waiter is not None:
                 self._pop_message_waiter.set_result(None)
                 self._pop_message_waiter = None
+
+
+def http_status_to_ws_code(http_status: int) -> int:
+    """Convert the provided http status to a websocket close code by adding 3000."""
+    return http_status + 3000

falcon/util/misc.py

@@ -458,10 +458,10 @@ def code_to_http_status(status):
 
     try:
         code = int(status)
-        if not 100 <= code <= 999:
-            raise ValueError('{} is not a valid status code'.format(status))
     except (ValueError, TypeError):
         raise ValueError('{!r} is not a valid status code'.format(status))
+    if not 100 <= code <= 999:
+        raise ValueError('{} is not a valid status code'.format(status))
 
     try:
         # NOTE(kgriffs): We do this instead of using http.HTTPStatus since

tests/asgi/test_misc.py

@@ -0,0 +1,32 @@
+# misc test for 100% coverage
+
+from unittest.mock import MagicMock
+
+import pytest
+
+from falcon.asgi import App
+from falcon.http_error import HTTPError
+from falcon.http_status import HTTPStatus
+
+
+@pytest.mark.asyncio
+async def test_http_status_not_impl():
+    app = App()
+    with pytest.raises(NotImplementedError):
+        await app._http_status_handler(MagicMock(), None, HTTPStatus(200), {}, None)
+
+
+@pytest.mark.asyncio
+async def test_http_error_not_impl():
+    app = App()
+    with pytest.raises(NotImplementedError):
+        await app._http_error_handler(MagicMock(), None, HTTPError(400), {}, None)
+
+
+@pytest.mark.asyncio
+async def test_python_error_not_impl():
+    app = App()
+    with pytest.raises(NotImplementedError):
+        await app._python_error_handler(
+            MagicMock(), None, ValueError('error'), {}, None
+        )

tests/asgi/test_ws.py

@@ -1092,3 +1092,126 @@ def test_msgpack_missing():
 
     with pytest.raises(RuntimeError):
         handler.deserialize(b'{}')
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize('status', [200, 500, 422, 400])
+@pytest.mark.parametrize('thing', [falcon.HTTPStatus, falcon.HTTPError])
+@pytest.mark.parametrize('accept', [True, False])
+async def test_ws_http_error_or_status_response(conductor, status, thing, accept):
+    class Resource:
+        async def on_websocket(self, req, ws):
+            if accept:
+                await ws.accept()
+            raise thing(status)
+
+    conductor.app.add_route('/', Resource())
+    exp_code = 3000 + status
+
+    async with conductor as c:
+        if accept:
+            async with c.simulate_ws() as ws:
+                assert ws.closed
+                assert ws.close_code == exp_code
+        else:
+            with pytest.raises(falcon.WebSocketDisconnected) as err:
+                async with c.simulate_ws():
+                    pass
+            assert err.value.code == exp_code
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize('status', [200, 500, 422, 400])
+@pytest.mark.parametrize(
+    'thing',
+    [
+        falcon.HTTPStatus,
+        falcon.HTTPError,
+    ],
+)
+@pytest.mark.parametrize('place', ['request', 'resource'])
+async def test_ws_http_error_or_status_middleware(conductor, status, thing, place):
+    called = False
+
+    class Resource:
+        async def on_websocket(self, req, ws):
+            nonlocal called
+            called = True
+
+    class Middleware:
+        async def process_request_ws(self, req, ws):
+            if place == 'request':
+                raise thing(status)
+
+        async def process_resource_ws(self, req, ws, res, params):
+            if place == 'resource':
+                raise thing(status)
+
+    conductor.app.add_route('/', Resource())
+    conductor.app.add_middleware(Middleware())
+    exp_code = 3000 + status
+
+    async with conductor as c:
+        with pytest.raises(falcon.WebSocketDisconnected) as err:
+            async with c.simulate_ws():
+                pass
+        assert err.value.code == exp_code
+    assert not called
+
+
+class FooBarError(Exception):
+    pass
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize('status', [200, 500, 422, 400])
+@pytest.mark.parametrize('thing', [falcon.HTTPStatus, falcon.HTTPError])
+@pytest.mark.parametrize(
+    'place', ['request', 'resource', 'ws_before_accept', 'ws_after_accept']
+)
+@pytest.mark.parametrize('handler_has_ws', [True, False])
+async def test_ws_http_error_or_status_error_handler(
+    conductor, status, thing, place, handler_has_ws
+):
+    class Resource:
+        async def on_websocket(self, req, ws):
+            if place == 'ws_before_accept':
+                raise FooBarError
+            await ws.accept()
+            if place == 'ws_after_accept':
+                raise FooBarError
+
+    class Middleware:
+        async def process_request_ws(self, req, ws):
+            if place == 'request':
+                raise FooBarError
+
+        async def process_resource_ws(self, req, ws, res, params):
+            if place == 'resource':
+                raise FooBarError
+
+    if handler_has_ws:
+
+        async def handle_foobar(req, resp, ex, param, ws=None):   # type: ignore
+            raise thing(status)
+
+    else:
+
+        async def handle_foobar(req, resp, ex, param):  # type: ignore
+            raise thing(status)
+
+    conductor.app.add_route('/', Resource())
+    conductor.app.add_middleware(Middleware())
+    conductor.app.add_error_handler(FooBarError, handle_foobar)
+    exp_code = 3000 + status
+
+    async with conductor as c:
+        if place == 'ws_after_accept':
+            async with c.simulate_ws() as ws:
+                assert ws.closed
+                assert ws.close_code == exp_code
+        else:
+            with pytest.raises(falcon.WebSocketDisconnected) as err:
+                async with c.simulate_ws():
+                    pass
+            assert err.value.code == exp_code

tests/test_utils.py

@@ -522,7 +522,23 @@ def test_get_http_status(self):
     def test_code_to_http_status(self, v_in, v_out):
         assert falcon.code_to_http_status(v_in) == v_out
 
-    @pytest.mark.parametrize('v', [0, 13, 99, 1000, 1337.01, -99, -404.3, -404, -404.3])
+    @pytest.mark.parametrize(
+        'v',
+        [
+            0,
+            13,
+            99,
+            1000,
+            1337.01,
+            -99,
+            -404.3,
+            -404,
+            -404.3,
+            'Successful',
+            'Failed',
+            None,
+        ],
+    )
     def test_code_to_http_status_value_error(self, v):
         with pytest.raises(ValueError):
             falcon.code_to_http_status(v)