@async and silent crash

[bdeonovic]

If an @async block encounters an error it silently stops running. Any way to at least print out some errors?

[JeffBezanson]

To find out that a Task exited with an error, somebody has to look. You can inspect t.exception, or wait, which will propagate the exception:

julia> t = @async error("hello")
Task (failed) @0x0000000003a74870

julia> wait(t)
ERROR: hello
 in wait at ./task.jl:53

julia> t.exception
ErrorException("hello")

The operations "see if task failed" and "print error message" are separated, so you can do one without the other.

[fonsp]

For anyone struggling with this problem, here's a version of @async that prints errors to the terminal immediately:

"Like @async except it prints errors to the terminal. 👶"
macro asynclog(expr)
    quote
        @async try
            $(esc(expr))
        catch ex
            bt = stacktrace(catch_backtrace())
            showerror(stderr, ex, bt)
            rethrow(ex)
        end
    end
end

[notinaboat]

Thanks @fonsp !
https://github.com/notinaboat/AsyncLog.jl