DO NOT MERGE

Trying to demonstrate that the test will not even fail when too many bytes are sent.

aiohttp/http_writer.py

@@ -123,7 +123,6 @@ async def write(
             if self.length >= chunk_len:
                 self.length = self.length - chunk_len
             else:
-                chunk = chunk[: self.length]
                 self.length = 0
                 if not chunk:
                     return

aiohttp/web_fileresponse.py

@@ -114,7 +114,7 @@ async def _sendfile_fallback(
         chunk_size = self._chunk_size
         loop = asyncio.get_event_loop()
         chunk = await loop.run_in_executor(
-            None, self._seek_and_read, fobj, offset, min(chunk_size, count)
+            None, self._seek_and_read, fobj, offset, chunk_size
         )
         while chunk:
             await writer.write(chunk)

tests/test_web_sendfile_functional.py

@@ -1179,9 +1179,15 @@ async def handler(request: web.Request) -> web.FileResponse:
     app.router.add_get("/", handler)
     client = await aiohttp_client(app)
 
-    resp = await client.get("/", headers={"Range": "bytes=20-40"})
-    assert resp.status == 206
-    body = await resp.read()
+    async with await client.get("/", headers={"Range": "bytes=20-40"}) as resp:
+        assert resp.status == 206
+        assert resp.headers["content-length"] == "21"
+        body = await resp.read()
+
+    async with await client.get("/", headers={"Range": "bytes=20-40"}) as resp:
+        assert resp.status == 206
+        assert resp.headers["content-length"] == "21"
+        body2 = await resp.read()
 
     # 21 bytes, because http range headers are including both fenceposts.
     assert len(body) == 21
@@ -1191,3 +1197,5 @@ async def handler(request: web.Request) -> web.FileResponse:
         f.seek(20)
         content = f.read(21)
         assert content == body
+
+    assert body == body2