Fix overshadowing of overlapped subbaps prefixes (aio-libs#3701).

CHANGES/3701.bugfix

@@ -0,0 +1 @@
+Fix overshadowing of overlapped subbaps prefixes.

CONTRIBUTORS.txt

@@ -84,6 +84,7 @@ Eric Sheng
 Erich Healy
 Eugene Chernyshov
 Eugene Naydenov
+Eugene Nikolaiev
 Eugene Tolmachev
 Evert Lammerts
 FichteFoll

aiohttp/web_urldispatcher.py

@@ -698,7 +698,8 @@ def get_info(self) -> Dict[str, Any]:
                 'prefix': self._prefix}
 
     async def resolve(self, request: Request) -> _Resolve:
-        if not request.url.raw_path.startswith(self._prefix):
+        if not request.url.raw_path.startswith(self._prefix + '/') and \
+                request.url.raw_path != self._prefix:
             return None, set()
         match_info = await self._app.router.resolve(request)
         match_info.add_app(self._app)

tests/test_urldispatch.py

@@ -1246,3 +1246,47 @@ def test_prefixed_subapp_resource_canonical(app) -> None:
     subapp = web.Application()
     res = subapp.add_subapp(canonical, subapp)
     assert res.canonical == canonical
+
+
+async def test_prefixed_subapp_overlap(app) -> None:
+    """
+    Subapp should not overshadow other subapps with overlapping prefixes
+    """
+    subapp1 = web.Application()
+    handler1 = make_handler()
+    subapp1.router.add_get('/a', handler1)
+    app.add_subapp('/s', subapp1)
+
+    subapp2 = web.Application()
+    handler2 = make_handler()
+    subapp2.router.add_get('/b', handler2)
+    app.add_subapp('/ss', subapp2)
+
+    match_info = await app.router.resolve(make_mocked_request('GET', '/s/a'))
+    assert match_info.route.handler is handler1
+    match_info = await app.router.resolve(make_mocked_request('GET', '/ss/b'))
+    assert match_info.route.handler is handler2
+
+
+async def test_prefixed_subapp_empty_route(app) -> None:
+    subapp = web.Application()
+    handler = make_handler()
+    subapp.router.add_get('', handler)
+    app.add_subapp('/s', subapp)
+
+    match_info = await app.router.resolve(make_mocked_request('GET', '/s'))
+    assert match_info.route.handler is handler
+    match_info = await app.router.resolve(make_mocked_request('GET', '/s/'))
+    assert "<MatchInfoError 404: Not Found>" == repr(match_info)
+
+
+async def test_prefixed_subapp_root_route(app) -> None:
+    subapp = web.Application()
+    handler = make_handler()
+    subapp.router.add_get('/', handler)
+    app.add_subapp('/s', subapp)
+
+    match_info = await app.router.resolve(make_mocked_request('GET', '/s/'))
+    assert match_info.route.handler is handler
+    match_info = await app.router.resolve(make_mocked_request('GET', '/s'))
+    assert "<MatchInfoError 404: Not Found>" == repr(match_info)