StaticResource only matches folder-like URL prefix

CHANGES/5250.bugfix

@@ -0,0 +1 @@
+StaticResource prefixes no longer match URLs with a non-folder prefix. For example ``routes.static('/foo', '/foo')`` no longer matches the URL ``/foobar``. Previously, this would attempt to load the file ``/foo/ar``.

CONTRIBUTORS.txt

@@ -76,6 +76,7 @@ Claudiu Popa
 Colin Dunklau
 Cong Xu
 Damien Nadé
+Dan King
 Dan Xu
 Daniel García
 Daniel Grossmann-Kavanagh

aiohttp/web_urldispatcher.py

@@ -495,6 +495,7 @@ def __init__(self, prefix: str, *, name: Optional[str] = None) -> None:
         assert prefix in ("", "/") or not prefix.endswith("/"), prefix
         super().__init__(name=name)
         self._prefix = _requote_path(prefix)
+        self._prefix2 = self._prefix + "/"
 
     @property
     def canonical(self) -> str:
@@ -505,6 +506,7 @@ def add_prefix(self, prefix: str) -> None:
         assert not prefix.endswith("/")
         assert len(prefix) > 1
         self._prefix = prefix + self._prefix
+        self._prefix2 = self._prefix + "/"
 
     def raw_match(self, prefix: str) -> bool:
         return False
@@ -616,7 +618,7 @@ async def resolve(self, request: Request) -> _Resolve:
         path = request.rel_url.raw_path
         method = request.method
         allowed_methods = set(self._routes)
-        if not path.startswith(self._prefix):
+        if not path.startswith(self._prefix2) and path != self._prefix:
             return None, set()
 
         if method not in allowed_methods:
@@ -732,7 +734,7 @@ def get_info(self) -> _InfoDict:
 
     async def resolve(self, request: Request) -> _Resolve:
         if (
-            not request.url.raw_path.startswith(self._prefix + "/")
+            not request.url.raw_path.startswith(self._prefix2)
             and request.url.raw_path != self._prefix
         ):
             return None, set()

tests/test_web_urldispatcher.py

@@ -461,6 +461,21 @@ async def test_static_absolute_url(aiohttp_client: Any, tmp_path: Any) -> None:
     assert resp.status == 403
 
 
+async def test_for_issue_5250(aiohttp_client: Any, tmp_path: Any) -> None:
+    app = web.Application()
+    app.router.add_static("/foo", tmp_path)
+
+    async def get_foobar(request):
+        return web.Response(body="success!")
+
+    app.router.add_get("/foobar", get_foobar)
+
+    client = await aiohttp_client(app)
+    async with await client.get("/foobar") as resp:
+        assert resp.status == 200
+        assert (await resp.text()) == "success!"
+
+
 @pytest.mark.xfail(
     raises=AssertionError,
     reason="Regression in v3.7: https://github.com/aio-libs/aiohttp/issues/5621",