Yeah I looked for this initially, but I wasn't able to find a way to override the flag 🤔

I originally tried something like:

cargoBuildFlags = [ "--target" "wasm32-unknown-unknown" ];

but then the actual build command just ended up with two commands: one for aarch64-apple-darwin and another for wasm32-unknown-unknown.

That lead me to these docs mentioning that the target is derived from the stdenv.hostPlatform.rust.rustcTarget, and digging into that eventually lead me to pkgsCross.wasm32-unknown-none.

Sidenote: I'm very curious about buildRustCrate btw - will have to investigate that another night!

Yeah I looked for this initially, but I wasn't able to find a way to override the flag 🤔

I originally tried something like:

cargoBuildFlags = [ "--target" "wasm32-unknown-unknown" ];

but then the actual build command just ended up with two targets: one for aarch64-apple-darwin and another for wasm32-unknown-unknown.

That lead me to these docs mentioning that the target is derived from the stdenv.hostPlatform.rust.rustcTarget, and digging into that eventually lead me to pkgsCross.wasm32-unknown-none.

Sidenote: I'm very curious about buildRustCrate btw - will have to investigate that another night!

In reply to @kranzes:matrix.org
Don't bother with buildRustCrate and crate2nix

Update: while the above^ works on aarch64-darwin as the build machine, I'm now running into issues when using x86_64-linux as the build machine.

It looks like even when just building a hello-world rust program with rustPlatform.buildrustPackage via pkgs.pkgsCross.wasm32-unknown-none.callPackage, it starts compiling LLVM and then rustc from scratch.

This was kind of expected after my experience on my mac, where the same happened, however on the mac they at least complete successfully after an hour or two. On my linux build machine, rustc fails to build during the bootstrap phase with a libunwind .so not found error.

Shouldn't llvm and rustc be cached for the pkgsCross.wasm32-unknown-none? Perhaps they're not, because there are no packages that actually use pkgsCross.wasm32-unknown-none, so as a result hydra never builds and caches them?

If so, what would be the best way to get hydra testing and building these? Would I need to add some simple hello-world-rust-wasm32-unknown-none package to pkgs/by-name/he/ or something along these lines?

I guess working out why rustc won't build is another issue, but at least with some basic package

Also, another thing I'm noticing is that regardless of what I put in meta.platforms, it always says the system is unsupported when building with pkgsCross.wasm32-unknown-none, and I always have to add NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 and --impure everytime I build 🫠 I might look into addressing this too.