`using` loads modules on workers but does not put exported bindings in Main

[simonster]

This may be intended, but it seems a bit awkward to me:

$ julia -p 1
[...]
  | | |_| | | | (_| |  |  Version 0.4.0-dev+1922 (2014-12-02 23:10 UTC)
 _/ |\__'_|_|_|\__'_|  |  Commit e4e1688* (0 days old master)
|__/                   |  x86_64-apple-darwin14.0.0

julia> using StatsBase

julia> @everywhere assert(isa(StatsBase.sample, Function))

julia> @everywhere assert(isa(sample, Function))
exception on 2: ERROR: sample not defined
 in eval at /usr/local/julia/base/sysimg.jl:7
 in anonymous at multi.jl:1395
 in anonymous at multi.jl:820
 in run_work_thunk at multi.jl:593
 in run_work_thunk at multi.jl:602
 in anonymous at task.jl:6

Obviously the workaround is @everywhere using StatsBase, but I think that using X should probably be equivalent to @everywhere using X, or if not, it should act exclusively on the main process. Instead it seems we get using X on the main process and require("X") on the workers.

[malmaud]

I'm going to label this as a bug since it seems clear that this couldn't have been the intended semantics.

[tlnagy]

I've been bitten by this loaded-but-still-out-scope bug several times. And no one I've pointed this out to has any idea why this is the way this is.

[timholy]

I don't think it's intentional, I just think that no one has yet decided that they care enough to fix it. You could be the one!

[tlnagy]

@timholy Any idea where the definition of using is located? It's kind of hard to grep for.

[yuyichao]

IIUC require(::Symbol)

[amitmurthy]

I think we need to fix this in the 0.5 timeframe itself. @everywhere using Mod or @everywhere require are problematic in themselves and responsible for JuliaLang/julia#12381 and probably JuliaLang/julia#16788

Which Julia/C function is called with using?

Base.require(:JSON) is equivalent of import JSON on all nodes.

[timholy]

It would be a bit annoying to go another release without fixing it. I once (long ago) spent a couple tens of minutes on this, but didn't get far enough to figure out how to do it or even to fully trace how using actually works.