[quietbritishjim]

I think the comment was about async in general, not just Rust (although that's the topic of OP).

In Python, cancellation causes an exception to be injected at the await site, which allows it to clean up whatever resources it likes (even if that means making other async calls). If you use Trio or the new TaskGroup in asyncio (inspired by Trio) then an exception leaking out of one task causes the others to be cancelled, and then the task group waits for all tasks to complete (successfully, with exception, or cancelled). It's extremely nice and easy to write reliable programs.

In principle, I think many of these ideas could be applied to threaded IO. But I haven't seen it done in practice.

[gpderetta]

> In principle, I think many of these ideas could be applied to threaded IO.

That's how POSIX deferred [1] cancellation works. An uncatchable exception is thrown from blocking calls if a thread is requested to terminate. As POSIX is C centered, you can imagine that handling exceptions was never popular, but it should work fine in C++. For some reasons it wasn't added to std::thread though.

[1] there is also async cancellation, but friends do not let friends use PTHREAD_CANCEL_ASYNCHRONOUS.

[heavenlyblue]

> In Python, cancellation causes an exception to be injected at the await site, which allows it to clean up whatever resources it likes (even if that means making other async calls). If you use Trio or the new TaskGroup in asyncio (inspired by Trio) then an exception leaking out of one task causes the others to be cancelled, and then the task group waits for all tasks to complete (successfully, with exception, or cancelled). It's extremely nice and easy to write reliable programs.

But not in JavaScript.