[Bug] Cannot start nix-shell on macOS about qmk_firmware

[sigprof]

The only way I can test the macOS support is by using the free GitHub runners, and apparently the current shell.nix works there (e.g., the latest run at the moment is https://github.com/sigprof/qmk-nix-support/actions/runs/6674858226/job/18142204580). But the macOS version used by GitHub for macos-latest runners is apparently still 12.7; the Nix version is the default for cachix/install-nix-action, which is 2.17.0 at the moment.

However, if your Mac is actually based on Apple Silicon, the existing shell.nix probably won't work (in fact, I can reproduce a similar evaluation error by trying to run nix-shell --system aarch64-darwin). The Nixpkgs snapshot that's used currently is probably too old to have proper aarch64-darwin support.

I also have some code that uses a more recent Nixpkgs snapshot (https://github.com/sigprof/nix-devenv-qmk); apparently the evaluation for aarch64-darwin also fails with that code, but with a much more clearer error message:

error: Package ‘avr-stage-final-gcc-wrapper-8.5.0’ in /nix/store/apfgz0vlvsmlifhqh6x0k2aih1jw3ikz-nixpkgs-src/pkgs/build-support/cc-wrapper/default.nix:628 is not available on the requested hostPlatform:
         hostPlatform.config = "aarch64-apple-darwin"
         package.meta.platforms = [
           "i686-cygwin"
           "x86_64-cygwin"
           "x86_64-darwin"
           "i686-darwin"
           "aarch64-darwin"
           "armv7a-darwin"
           "i686-freebsd13"
           "x86_64-freebsd13"
           "x86_64-solaris"
           "aarch64-linux"
           "armv5tel-linux"
           "armv6l-linux"
           "armv7a-linux"
           "armv7l-linux"
           "i686-linux"
           "loongarch64-linux"
           "m68k-linux"
           "microblaze-linux"
           "microblazeel-linux"
           "mips-linux"
           "mips64-linux"
           "mips64el-linux"
           "mipsel-linux"
           "powerpc64-linux"
           "powerpc64le-linux"
           "riscv32-linux"
           "riscv64-linux"
           "s390-linux"
           "s390x-linux"
           "x86_64-linux"
           "aarch64-netbsd"
           "armv6l-netbsd"
           "armv7a-netbsd"
           "armv7l-netbsd"
           "i686-netbsd"
           "m68k-netbsd"
           "mipsel-netbsd"
           "powerpc-netbsd"
           "riscv32-netbsd"
           "riscv64-netbsd"
           "x86_64-netbsd"
           "i686-openbsd"
           "x86_64-openbsd"
           "x86_64-redox"
         ]
         package.meta.badPlatforms = [
           "aarch64-darwin"
         ]
       , refusing to evaluate.

So it seems that the underlying reason for the error is that at least the AVR cross toolchain is broken on aarch64-darwin. Adding --arg avr false may help if you don't actually need AVR support. Another thing you may try is changing pkgsCross.avr.buildPackages.gcc8 to pkgsCross.avr.buildPackages.gcc (this way you would get avr-gcc 12.3.0, which may produce larger binaries than 8.5.0, but it might be good enough).

And yet another option that you may try is to use the Rosetta emulation: nix-shell --system x86_64-darwin.

[synecdokey]

I am indeed on apple silicon! --arg avr false is something I tried since I didn't need it, but didn't work out. But using your devenv (with --arg avr false) worked like a charm, many thanks for getting me unblocked. ☺️