Return the first argument in put!

[tkf]

push! usually returns the first argument ("container")

julia> push!([], 1)
1-element Array{Any,1}:
 1

julia> push!(Dict(), :a => 1)
Dict{Any,Any} with 1 entry:
  :a => 1

julia> push!(Set(), 1)
Set{Any} with 1 element:
  1

but not with channels

julia> push!(Channel(Inf), 1)
1

This PR fixes this inconsistency by tweaking put! such that put!(c, _) === c. This automatically fixes push! as push! is just an alias of put!:

julia/base/channels.jl

Line 351 in 2835347

push!(c::Channel, v) = put!(c, v)

This also makes put!(::Channel, _) consistent with put!(::RemoteChannel, _)

julia/stdlib/Distributed/src/remotecall.jl

Lines 584 to 591 in 2835347

	"""
	put!(rr::RemoteChannel, args...)
	Store a set of values to the [`RemoteChannel`](@ref).
	If the channel is full, blocks until space is available.
	Return the first argument.
	"""
	put!(rr::RemoteChannel, args...) = (call_on_owner(put_ref, rr, myid(), args...); rr)

[StefanKarpinski]

Perhaps that should be the distinction between push and put for channels?

[tkf]

Sounds reasonable to me. But in this case, ideally, I think put!(::RemoteChannel, v) should then be re-defined to return v and the vararg form put!(::RemoteChannel, args...) should be deprecated (or maybe return args[end]?) for consistency. This is technically more breaking as the docstring for put!(::RemoteChannel, args...) explicitly says "Return the first argument." Perhaps this has to be postponed until 2.0?

Maybe the option with least pain is to just define

push!(c::AbstractChannel, v) = (put!(c, v); c)

and leave put! methods as-is. This would let people use Channel and RemoteChannel with a consistent API.

[TotalVerb]

put! for a Future also returns the first argument, which is very useful for e.g. creating an immediately resolved future put!(Future(), x). So for consistency, I'd also prefer put! to return the channel when the first argument is a channel. It is not too bad to do v = value; put!(c, v); v in the cases where the value is actually needed.