If you have an aarch64 version of juliaup which runs, then if someone tries to install an x64 version of Julia, you should verify that you can run Intel processes, and if you can't prompt the user to install Rosetta 2. E.g. something like try to run arch -x86_64 /bin/bash -c "arch", which says "run x86_64 bash and tell it to print out the current architecture". If it prints out i386, then you know it's running through Rosetta, and all is good. I'm not sure what the failure mode is; perhaps it automatically prompts to install Rosetta? If it doesn't, you can manually prompt to install rosetta via softwareupdate --install-rosetta

I'm tempted to leave as is and not do anything here in the short term, because we are now going to make the aarch64 build the default on M1 once 1.8.0 ships, which doesn't seem that far off.

Is there anything to be done here? I think ARM builds are the default for current Julia versions?

Or, put differently: What would be a scenario where this is needed?

I tried but couldn't think of any: all new Julia versions offer ARM binaries anyway. And if the user tries to install e.g. Julia 1.0, wouldn't that still work? I.e. downloading and placing the executable in the right place all don't care about the architecture of the binary. Of course launching it does, but wouldn't macOS just recognize that the user attempted to launch an x86 binary, and in that case offer to install Rosetta, if it isn't already?

What am I missing?

@fingolfin I think the problem is (or at least was when I tried this ages ago) that launching say julia 1.0 did not automatically offer to install Rosetta, but instead there was just an unhelpful error message if it wasn't installed already.

I'm tempted to not do anything about this and just leave it as a corner case. No one has ever complained about this in many years :)

I feel like we can close this one.