How to define a macro via Package Extension?

Nice, you could also do something a bit more ugly without directly importing but your solution does look cleaner:

julia> module TESTT
       macro asd end
       end

julia> import .TESTT

julia> TESTT.var"@asd"(__source__::LineNumberNode, __module__::Module, x) = 15

julia> TESTT.@asd 0
15
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