[3.12] gh-127655: Ensure `_SelectorSocketTransport.writelines` pauses the protocol...

gh-127655: Ensure `_SelectorSocketTransport.writelines` pauses the protocol if needed (GH-127656)

Ensure `_SelectorSocketTransport.writelines` pauses the protocol if it reaches the high water mark as needed.
(cherry picked from commit e991ac8f2037d78140e417cc9a9486223eb3e786)

Co-authored-by: J. Nick Koston <nick@koston.org>
Co-authored-by: Kumar Aditya <kumaraditya@python.org>

diff --git a/Lib/asyncio/selector_events.py b/Lib/asyncio/selector_events.py
index 790711f834096bdb377dbdea6126609f9279cca1..dd79ad18df3b18a8fc8af40ca642dd5387ac3ec2 100644 (file)
--- a/Lib/asyncio/selector_events.py
+++ b/Lib/asyncio/selector_events.py
@@ -1183,6 +1183,7 @@ class _SelectorSocketTransport(_SelectorTransport):
         # If the entire buffer couldn't be written, register a write handler
         if self._buffer:
             self._loop._add_writer(self._sock_fd, self._write_ready)
+            self._maybe_pause_protocol()
 
     def can_write_eof(self):
         return True

diff --git a/Lib/test/test_asyncio/test_selector_events.py b/Lib/test/test_asyncio/test_selector_events.py
index 47693ea4d3ce2e0b5709764de9302f4db5537bad..736c19796ef3fc7f33bd2d5cf0ed59805bb09903 100644 (file)
--- a/Lib/test/test_asyncio/test_selector_events.py
+++ b/Lib/test/test_asyncio/test_selector_events.py
@@ -805,6 +805,18 @@ class SelectorSocketTransportTests(test_utils.TestCase):
         self.assertTrue(self.sock.send.called)
         self.assertTrue(self.loop.writers)
 
+    def test_writelines_pauses_protocol(self):
+        data = memoryview(b'data')
+        self.sock.send.return_value = 2
+        self.sock.send.fileno.return_value = 7
+
+        transport = self.socket_transport()
+        transport._high_water = 1
+        transport.writelines([data])
+        self.assertTrue(self.protocol.pause_writing.called)
+        self.assertTrue(self.sock.send.called)
+        self.assertTrue(self.loop.writers)
+
     @unittest.skipUnless(selector_events._HAS_SENDMSG, 'no sendmsg')
     def test_write_sendmsg_full(self):
         data = memoryview(b'data')

diff --git a/Misc/NEWS.d/next/Security/2024-12-05-21-35-19.gh-issue-127655.xpPoOf.rst b/Misc/NEWS.d/next/Security/2024-12-05-21-35-19.gh-issue-127655.xpPoOf.rst
new file mode 100644 (file)
index 0000000..76cfc58
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2024-12-05-21-35-19.gh-issue-127655.xpPoOf.rst
@@ -0,0 +1 @@
+Fixed the :class:`!asyncio.selector_events._SelectorSocketTransport` transport not pausing writes for the protocol when the buffer reaches the high water mark when using :meth:`asyncio.WriteTransport.writelines`.