axelson
Technique to allow a function call only within a macro
I’m playing around with creating a rather unidiomatic testing library and I’d like to constrain a macro call of a macro that my library exposes to only be available within the do block of one of the macros that my library defines. Is there a way to do that with some meta programming?
Here’s an example of what I mean:
import MyLib, only: [:lib_setup]
# Should succeed
lib_setup do
MyLib.other_macro(42)
end
# Should fail (at compiletime or runtime)
MyLib.other_macro(42)
And the reason that I want to constrain it like so is because of how unidiomatic other_macro is.
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zachallaun
In your example, having only imported :lib_setup and not run require MyLib, the second call would fail and the only way for the first call to succeed would be if the lib_setup call had traversed the do block and transformed the inner call into something that could succeed.
If that particular behavior wasn’t intended in the example, one option to “communicate” between macros is for lib_setup to set a module attribute at the beginning of the returned quote and unset it at the end, and then the inner macro can look for the presence of that attribute to ensure it’s being called in a proper context.
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