Conditional use of modules and macros

New to Julia
1

It seems using a module can be done at arbitrary places within source files, even in conditional blocks, without too much trouble, except for when a module provides a macro that you would otherwise use. For example, this will not work:

paulm@cmstorm 15:27:~$ cat fail.jl 
if false
    using Profile
    @profile main()
end

paulm@cmstorm 15:27:~$ julia fail.jl
ERROR: LoadError: LoadError: UndefVarError: @profile not defined
in expression starting at /home/paulm/fail.jl:3
in expression starting at /home/paulm/fail.jl:1

I assume the compiler wants/needs to do macro expansion, even though the code block obviously will never get executed.

One workaround here would be to manually expand @profile, which is quite small. But this would get annoying (and error prone, especially over time) for larger macros. Any other tricks to conditionally use a module and its macros like this?

2

Maybe you are looking for

3

I believe you can use @static for this, e.g.

@static if false
    using Profile
    @profile main()
end

which would not try to expand the macro.

4

Well, that indeed works for the false case. But I just noticed that the true case doesn’t work anyway:

melis@juggle 17:38:~$ cat t.jl 
if true
    using Profile
    @profile main()
end
melis@juggle 17:38:~$ julia t.jl 
ERROR: LoadError: LoadError: UndefVarError: @profile not defined
in expression starting at /home/melis/t.jl:3
in expression starting at /home/melis/t.jl:1
5

This fails for the same reason stated here, you need to split this into 2 “@static if…” clauses so the import is resolved before the macro is expanded

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