What's the right way to unwrap a `TaskFailedException`?

General Usage
1

What’s the right way to unwrap a TaskFailedException? err.task.exception.task.exception gives me the original exception, but that seems very brittle.

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2

Turns out I just got confused because I had two nested TaskFailedExceptions without realizing.

julia> t = @async 0//0;

julia> err = try
       wait(t)
       catch err
       err
       end
TaskFailedException(Task (failed) @0x00007f886e84bd00)

julia> err.task.exception
ArgumentError("invalid rational: zero(Int64)//zero(Int64)")

seems totally fine.

3 
julia> t
Task (failed) @0x000000011347f310
ArgumentError: invalid rational: zero(Int64)//zero(Int64)
4

That’s not particularly helpful, since

julia> typeof(t)
Task

So while this is pretty printed I can’t actually do anything with it.

5

ok, but

julia> t.result
ArgumentError("invalid rational: zero(Int64)//zero(Int64)")
6

Sure, that’s basically what I wrote above, no? Except with exception instead of result.

7

I wanted only to point out, that having the task variable t or a channel – if it happens to be bound to a channel –, you have direct access to the exception without wrapping it in a try - catch block. I use it all the time.

1 Like
8

Right, makes sense.
This did indeed come up in the context of iterating over a Channel (returned from walkdir), but it seems easier to look at the caught exception than accessing the channel directly to me.

1 Like