Root app middleware receives wrong app context

CHANGES/2550.bugfix

@@ -0,0 +1 @@
+Make `request.app` point to proper application instance when using nested applications (with middlewares).

aiohttp/web.py

@@ -22,6 +22,7 @@
 from .web_exceptions import *  # noqa
 from .web_fileresponse import *  # noqa
 from .web_middlewares import *  # noqa
+from .web_middlewares import _fix_request_current_app
 from .web_protocol import *  # noqa
 from .web_request import *  # noqa
 from .web_response import *  # noqa
@@ -267,6 +268,8 @@ def _prepare_middleware(self):
                               'see #2252'.format(m),
                               DeprecationWarning, stacklevel=2)
                 yield m, False
+        if self._middlewares:
+            yield _fix_request_current_app(self), True
 
     async def _handle(self, request):
         match_info = await self._router.resolve(request)
@@ -298,8 +301,9 @@ async def _handle(self, request):
             ("Handler {!r} should return response instance, "
              "got {!r} [middlewares {!r}]").format(
                  match_info.handler, type(resp),
-                 [middleware for middleware in app.middlewares
-                  for app in match_info.apps])
+                 [middleware
+                  for app in match_info.apps
+                  for middleware in app.middlewares])
         return resp
 
     def __call__(self):

aiohttp/web_middlewares.py

@@ -78,3 +78,12 @@ async def impl(request, handler):
         return await handler(request)
 
     return impl
+
+
+def _fix_request_current_app(app):
+
+    @middleware
+    async def impl(request, handler):
+        with request.match_info.set_current_app(app):
+            return await handler(request)
+    return impl

aiohttp/web_request.py

@@ -609,10 +609,10 @@ def match_info(self):
         """Result of route resolving."""
         return self._match_info
 
-    @reify
+    @property
     def app(self):
         """Application instance."""
-        return self._match_info.apps[-1]
+        return self._match_info.current_app
 
     async def _prepare_hook(self, response):
         match_info = self._match_info

aiohttp/web_urldispatcher.py

@@ -10,6 +10,7 @@
 import warnings
 from collections import namedtuple
 from collections.abc import Container, Iterable, Sequence, Sized
+from contextlib import contextmanager
 from functools import wraps
 from pathlib import Path
 from types import MappingProxyType
@@ -170,6 +171,7 @@ def __init__(self, match_dict, route):
         super().__init__(match_dict)
         self._route = route
         self._apps = ()
+        self._current_app = None
         self._frozen = False
 
     @property
@@ -198,8 +200,26 @@ def apps(self):
     def add_app(self, app):
         if self._frozen:
             raise RuntimeError("Cannot change apps stack after .freeze() call")
+        if self._current_app is None:
+            self._current_app = app
         self._apps = (app,) + self._apps
 
+    @property
+    def current_app(self):
+        return self._current_app
+
+    @contextmanager
+    def set_current_app(self, app):
+        assert app in self._apps, (
+            "Expected one of the following apps {!r}, got {!r}"
+            .format(self._apps, app))
+        prev = self._current_app
+        self._current_app = app
+        try:
+            yield
+        finally:
+            self._current_app = prev
+
     def freeze(self):
         self._frozen = True
 

tests/test_web_functional.py

@@ -1290,6 +1290,41 @@ async def on_signal(app):
     assert [app, subapp1, subapp2] == order
 
 
+@pytest.mark.parametrize('route,expected', [
+    ('/sub/', ['app see root', 'subapp see sub']),
+    ('/', ['app see root']),
+])
+async def test_subapp_middleware_context(loop, test_client, route, expected):
+    values = []
+
+    def show_app_context(appname):
+        @web.middleware
+        async def middleware(request, handler):
+            values.append('{} see {}'.format(appname, request.app['my_value']))
+            return await handler(request)
+        return middleware
+
+    async def handler(request):
+        return web.Response(text='Ok')
+
+    app = web.Application()
+    app['my_value'] = 'root'
+    app.middlewares.append(show_app_context('app'))
+    app.router.add_get('/', handler)
+
+    subapp = web.Application()
+    subapp['my_value'] = 'sub'
+    subapp.middlewares.append(show_app_context('subapp'))
+    subapp.router.add_get('/', handler)
+    app.add_subapp('/sub/', subapp)
+
+    client = await test_client(app)
+    resp = await client.get(route)
+    assert 200 == resp.status
+    assert 'Ok' == await resp.text()
+    assert expected == values
+
+
 async def test_custom_date_header(loop, test_client):
 
     async def handler(request):