Improve handling of KeyboardInterrupt and task cancellation in SCP

This commit makes sure to re-raise CancelledError when an SCP operation
is cancelled, letting the calling code sees the exception and can decide
whether to cancel future operations or not. Thanks go to Viktor Kertesz
for reporting this issue and helping to understand the behavior in
various versions of Python.

This also includes a small change to abort an SCP session when
KeyboardInterrupt is raised, closing the session more quickly.

Author: ronf

asyncssh/scp.py

@@ -579,8 +579,9 @@ async def run(self, srcpath: _SCPPath) -> None:
             for name in await SFTPGlob(self._fs).match(srcpath):
                 await self._send_files(cast(bytes, name.filename),
                                             b'', name.attrs)
-        except asyncio.CancelledError:
+        except (KeyboardInterrupt, asyncio.CancelledError):
             cancelled = True
+            raise
         except (OSError, SFTPError) as exc:
             self.handle_error(exc)
         finally:
@@ -745,8 +746,9 @@ async def run(self, dstpath: _SCPPath) -> None:
                                              dstpath))
             else:
                 await self._recv_files(b'', dstpath)
-        except asyncio.CancelledError:
+        except (KeyboardInterrupt, asyncio.CancelledError):
             cancelled = True
+            raise
         except (OSError, SFTPError, ValueError) as exc:
             self.handle_error(exc)
         finally:
@@ -911,8 +913,9 @@ async def run(self) -> None:
 
         try:
             await self._copy_files()
-        except asyncio.CancelledError:
+        except (KeyboardInterrupt, asyncio.CancelledError):
             cancelled = True
+            raise
         except (OSError, SFTPError) as exc:
             self._handle_error(exc)
         finally:

tests/test_sftp.py

@@ -5047,9 +5047,10 @@ def _cancel(_srcpath, _dstpath, _bytes_copied, _total_bytes):
             self._create_file('src', 1024*8192 * 'a')
 
             coro = scp(src, dst, block_size=8192, progress_handler=_cancel)
-
             task = asyncio.create_task(coro)
-            await task
+
+            with self.assertRaises(asyncio.CancelledError):
+                await task
         finally:
             remove('src dst')