How to check that import module will succeed?

[evilrat]

On Friday, 26 July 2019 at 03:42:58 UTC, Andrey Zherikov wrote:
> Is there a way to check whether some module, say "foo", is 
> available for import before doing "import foo"?

I did some really retarded utility like this in the past, worked 
for me, but I can't say it is that well tested and there might be 
a better way (after all it just assumes that template 
instantiation failure can only mean there is no such module), so 
in short template allowed to fail, and we check if it is failed 
or not to test if desired module exists. Don't remember if static 
is really necessary or you can just return directly.

     bool isModuleAvailable(alias modName)() {
         mixin("import " ~ modName ~ ";");
         static if (__traits(compiles, mixin(modName).stringof))
             return true;
         else
             return false;
     }

     // use like this
     static if (__traits(compiles, isModuleAvailable!"mymod" ))
         import mymod;