How to intercept creation or setting of variable in current module?

General Usage
1

Need help, how to intercept operation on create new variable on current module in Julia 1.8?

For example, to intercept MyModule.x = 1 in Julia 1.8 i do this:

julia> module MyModule end;

julia> function Base.setproperty!(m::Module, p::Symbol, v)
           println("variable $p changed on $v in module $m")
           @eval m $p = $v  # waiting for julia 1.9 and will use setglobal!()
       end;

julia> MyModule.x = 1;
variable x changed on 1 in module Main.MyModule

How to intercept x = 1 in Main?

julia> Main.x = 1;
variable x changed on 1 in module Main

julia> x = 1;  # must print like Main.x = 1
2

Any ideas?

3

So you want to circumvent the restriction / error “cannot assign variables in other modules”?

Could you explain what you are trying to accomplish with this?

MyModule.x would be a global; so it should presumably be a const.

If you want specific variables to be assignable from the outside of MyModule, you could just write a function (in MyModule) to assign those values.
Do you really want to permit creation of arbitrary globals (with possible side effects)?

4

I must create a trigger on change or add the variable in the current module.

When a variable is created or modified in the current module, my function must be called.

This must happen regardless of how the module variable is created or modified. When julia> x=1 in Main too.

5

It would help to get a bigger picture idea of what you are trying to accomplish.

If you just need to run a function when a variable in MyModule is modified, can’t you ensure that the variable is modified by calling a function (MyModule.change_x())? Then change_x() can call the function you need to be called.

6

I can’t.

Variables in Main or any other module are created in a independent way.

I only must to call foo() when a module variable is created or modified.

If the variable was created in Main from the REPL like this:

julia> x = 1;

i must call foo() too.

7

Sorry - I don’t know how to accomplish this.

For curiosity - the pattern you are aiming for seems very unusual. Why do you need to create variables in a module from the REPL?

Perhaps the question to ask is: is this the right design choice?

8

I am trying to visualise the workspace without refresh all module variables by Base.names().