Fix omitting repeated dataloss warnings in HTTP11DownloadHandler. (#7222)

scrapy/core/downloader/handlers/http11.py

@@ -93,6 +93,7 @@ class HTTP11DownloadHandler(BaseDownloadHandler):
             "DOWNLOAD_FAIL_ON_DATALOSS"
         )
         self._disconnect_timeout: int = 1
+        self._fail_on_dataloss_warned: bool = False
 
     async def download_request(self, request: Request) -> Response:
         """Return a deferred for the HTTP download"""
@@ -115,8 +116,19 @@ class HTTP11DownloadHandler(BaseDownloadHandler):
             fail_on_dataloss=self._fail_on_dataloss,
             crawler=self._crawler,
         )
-        with wrap_twisted_exceptions():
-            return await maybe_deferred_to_future(agent.download_request(request))
+        try:
+            with wrap_twisted_exceptions():
+                return await maybe_deferred_to_future(agent.download_request(request))
+        except ResponseDataLossError:
+            if not self._fail_on_dataloss_warned:
+                logger.warning(
+                    "Got data loss in %s. If you want to process broken "
+                    "responses set the setting DOWNLOAD_FAIL_ON_DATALOSS = False"
+                    " -- This message won't be shown in further requests",
+                    request.url,
+                )
+                self._fail_on_dataloss_warned = True
+            raise
 
     async def close(self) -> None:
         from twisted.internet import reactor
@@ -633,7 +645,6 @@ class _ResponseReader(Protocol):
         self._maxsize: int = maxsize
         self._warnsize: int = warnsize
         self._fail_on_dataloss: bool = fail_on_dataloss
-        self._fail_on_dataloss_warned: bool = False
         self._reached_warnsize: bool = False
         self._bytes_received: int = 0
         self._certificate: ssl.Certificate | None = None
@@ -738,15 +749,6 @@ class _ResponseReader(Protocol):
                 self._finish_response(flags=["dataloss"])
                 return
 
-            if not self._fail_on_dataloss_warned:
-                logger.warning(
-                    "Got data loss in %s. If you want to process broken "
-                    "responses set the setting DOWNLOAD_FAIL_ON_DATALOSS = False"
-                    " -- This message won't be shown in further requests",
-                    self._txresponse.request.absoluteURI.decode(),
-                )
-                self._fail_on_dataloss_warned = True
-
             exc = ResponseDataLossError()
             exc.__cause__ = reason.value
             reason = Failure(exc)

tests/test_downloader_handler_twisted_http2.py

@@ -86,6 +86,9 @@ class TestHttps2(H2DownloadHandlerMixin, TestHttps11Base):
     def test_download_cause_data_loss(self) -> None:  # type: ignore[override]
         pytest.skip(self.HTTP2_DATALOSS_SKIP_REASON)
 
+    def test_download_cause_data_loss_double_warning(self) -> None:  # type: ignore[override]
+        pytest.skip(self.HTTP2_DATALOSS_SKIP_REASON)
+
     def test_download_allow_data_loss(self) -> None:  # type: ignore[override]
         pytest.skip(self.HTTP2_DATALOSS_SKIP_REASON)
 

tests/test_downloader_handlers_http_base.py

@@ -516,6 +516,21 @@ class TestHttp11Base(TestHttpBase):
             with pytest.raises(ResponseDataLossError):
                 await download_handler.download_request(request)
 
+    @deferred_f_from_coro_f
+    async def test_download_cause_data_loss_double_warning(
+        self, caplog: pytest.LogCaptureFixture, mockserver: MockServer
+    ) -> None:
+        request = Request(mockserver.url("/broken", is_secure=self.is_secure))
+        async with self.get_dh() as download_handler:
+            with pytest.raises(ResponseDataLossError):
+                await download_handler.download_request(request)
+            assert "Got data loss" in caplog.text
+            caplog.clear()
+            with pytest.raises(ResponseDataLossError):
+                await download_handler.download_request(request)
+            # no repeated warning
+            assert "Got data loss" not in caplog.text
+
     @pytest.mark.parametrize("url", ["broken", "broken-chunked"])
     @deferred_f_from_coro_f
     async def test_download_allow_data_loss(