Not possible to "share" top-level variables during precompilation?

I noticed the following behavior I’m trying to understand if its intentional, a bug, or could be changed. It seems obscure but has kind of come up as I’m trying to make Memoization.jl more precompile-friendly. On 1.9-beta2, imagine you have 2 packages:

module Foo
const caches = IdDict()
set_cache(x) = (@show(objectid(caches)); caches[x] = x)

module Bar
using Foo

Then you do

julia> using Bar
[ Info: Precompiling Bar [b60c06c0-7e54-11e8-3788-4bd722d65317]
objectid(caches) = 0x52bb3bf00c4b7e9d
objectid(caches) = 0x4de8dd67f96a789a

julia> Bar.Foo.caches
IdDict{Any, Any} with 1 entry:
  "foo" => "foo"

So as you can see, during precompilation, apparently, there’s are two different copies of caches created. And only the one created inside Foo I suppose persists to the actual session (and contains “foo”).

My question is whether this is intentional? Followup question, would there be a way to have a shared global object that is populated during precompilation from any module? Thanks.

One module owns the binding and the object being pointed to. The idiomatic way is to apply the changes that you want to make during __init__ in th second module.


That is one way, but __init__ functions are not particularly idiomatic. The common way to handle this (like Base.Docs) is to embed a variable within the new Module (Base.Docs.meta()) that contains the content relevant to that module.