Proposal: wait/fetch on Task

[iamed2]

Right now wait has the same meaning for almost everything: wait for something to be available or for something to happen. With Task, it means the above plus get a result. For AbstractRemoteRef, this is what fetch does.

I propose moving that functionality of Task to fetch. Here's what it would look like in 0.7:

function fetch(t::Task)
    if !istaskdone(t)
        if t.donenotify === nothing
            t.donenotify = Condition()
        end
    end
    while !istaskdone(t)
        wait(t.donenotify)
    end
    if istaskfailed(t)
        throw(t.exception)
    end
    return task_result(t)
end

@deprecate wait(t::Task) fetch(t)

and in 1.0:

function wait(t::Task)
    if !istaskdone(t)
        if t.donenotify === nothing
            t.donenotify = Condition()
        end
    end
    while !istaskdone(t)
        wait(t.donenotify)
    end
    if istaskfailed(t)
        throw(t.exception)
    end
end

function fetch(t::Task)
    wait(t::Task)
    return task_result(t)
end

How does this sound?

If this is not accepted I would still like to define fetch(t::Task) = wait(t), as it has a clear meaning and allows Tasks and Futures to be used interchangeably in some cases.

[iamed2]

Working on a PR now

[JeffBezanson]

Triage accepts.