should @sync unwrap TaskFailedExceptions when constructing CompositeException?

[oxinabox]

Right now we take any exception that occurs in a @sync block and just put it straight into a Composite exception

julia/base/task.jl

Lines 359 to 363 in b46df09

	catch e
	if !@isdefined(c_ex)
	c_ex = CompositeException()
	end
	push!(c_ex, e)

However large parts of @sync blocks are in turn @async statements, and any exception thrown from a @async statement will be a TaskFailedException.

There is a case to be made for unwrapping them.
(Arguably the same for CapturedExceptions with distributed)
Upside of unwrapping them is that this is probably what people want, it is the useful information.
Downside is it is a loss of information, someone might want the task.

I lean towards not doing this, and just doing #41300
at least at first, which should solve most of the pain.

[JeffBezanson]

Downside is it is a loss of information, someone might want the task.

Yes, this loses a lot of information, I don't think we should do it.

[nalimilan]

See also #38931.