How to delay the load of dependencies in a module to "using" time?

General Usage
1

Hi, community!

When a module is defined, such as in

module MyModule
using PyCall
end

the module PyCall will be loaded, even if you haven’t run using .MyModule.

The main question is: Is it possible to delay this load of dependencies to the time when you run using MyModule? and if possible, Is there an apparent reason for this to be a bad idea?

Thanks in advance!

2

See GitHub - JuliaPackaging/Requires.jl: Lazy code loading for Julia

3

Thanks @mkitti for your eager response, but I think that the package provided does not cover the use case I’m looking for.

I understand that Requires allows to trigger the execution of portions of code (such as using (...) ) after some other package is also loaded. What I want is to run portions of code after the module itself is loaded, which is subtly different, and (I think) is not covered.

4

You could either use requires and then trigger loading via @eval using MyLazyModule or maybe the later is sufficient.

5

You may want to take a close look at how Requires.jl works and examine thr consequences for precompilation and static compilation.

    if !isprecompiling() 
       listenpkg($pkg) do 
         withpath($srcfile) do 
           err($__module__, $modname, $srcfile, $srcline) do 
             $(esc(:(eval($(Expr(:quote, Expr(:block, 
                                             :(const $(Symbol(modname)) = Base.require($pkg)), 
                                             expr))))))) 
           end 
         end 
         $withnotifications($srcfile, $__module__, $idstr, $modname, $(esc(Expr(:quote, expr)))) 
       end 
     end
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