From 97981252628a9f6a9b80a0ea62d21907060ffcf0 Mon Sep 17 00:00:00 2001
From: "zainnadeem(RedOpsCell)" <zainnadeemzainnadeem80@gmail.com>
Date: Thu, 25 Jun 2026 22:24:47 +0500
Subject: [PATCH] gh-152099: Raise SendfileNotAvailableError for fallback
 transports

---
 Lib/asyncio/base_events.py                                   | 2 +-
 Lib/test/test_asyncio/test_sendfile.py                       | 5 +++--
 .../Library/2026-06-25-22-19-04.gh-issue-152099.L7fKq9.rst   | 4 ++++
 3 files changed, 8 insertions(+), 3 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2026-06-25-22-19-04.gh-issue-152099.L7fKq9.rst

diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
index e6c72e3d5b5487e..451ab76b7416542 100644
--- a/Lib/asyncio/base_events.py
+++ b/Lib/asyncio/base_events.py
@@ -1283,7 +1283,7 @@ async def sendfile(self, transport, file, offset=0, count=None,
                     raise
 
         if not fallback:
-            raise RuntimeError(
+            raise exceptions.SendfileNotAvailableError(
                 f"fallback is disabled and native sendfile is not "
                 f"supported for transport {transport!r}")
         return await self._sendfile_fallback(transport, file,
diff --git a/Lib/test/test_asyncio/test_sendfile.py b/Lib/test/test_asyncio/test_sendfile.py
index 7afd7de3bb936e6..38591629d71141e 100644
--- a/Lib/test/test_asyncio/test_sendfile.py
+++ b/Lib/test/test_asyncio/test_sendfile.py
@@ -354,7 +354,7 @@ def test_sendfile_not_supported(self):
         try:
             with self.assertRaisesRegex(RuntimeError, "not supported"):
                 self.run_loop(
-                    self.loop.sendfile(tr, self.file))
+                    self.loop.sendfile(tr, self.file, fallback=False))
             self.assertEqual(0, self.file.tell())
         finally:
             # don't use self.addCleanup because it produces resource warning
@@ -580,7 +580,8 @@ def test_sendfile_no_fallback_for_fallback_transport(self):
         transport = mock.Mock()
         transport.is_closing.side_effect = lambda: False
         transport._sendfile_compatible = constants._SendfileMode.FALLBACK
-        with self.assertRaisesRegex(RuntimeError, 'fallback is disabled'):
+        with self.assertRaisesRegex(asyncio.SendfileNotAvailableError,
+                                    'fallback is disabled'):
             self.loop.run_until_complete(
                 self.loop.sendfile(transport, None, fallback=False))
 
diff --git a/Misc/NEWS.d/next/Library/2026-06-25-22-19-04.gh-issue-152099.L7fKq9.rst b/Misc/NEWS.d/next/Library/2026-06-25-22-19-04.gh-issue-152099.L7fKq9.rst
new file mode 100644
index 000000000000000..05e760bcf6ed6d3
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-06-25-22-19-04.gh-issue-152099.L7fKq9.rst
@@ -0,0 +1,4 @@
+``asyncio``'s ``loop.sendfile(..., fallback=False)`` now consistently raises
+:exc:`asyncio.SendfileNotAvailableError` for fallback-only transports, such as
+SSL/TLS transports, when native sendfile cannot be used. Previously, this case
+raised :exc:`RuntimeError`.