Host component rust-docs doesn't support target aarch64-apple-darwin

[npajkovsky]

Hey,

I wanted to use your overlay and it seems, that it's not fully ready for aarch64-apple-darwin.

-> % home-manager build
error: Component resolution failed for rust-default-1.55.0
       - note: available extensions are cargo, clippy, clippy-preview, llvm-tools-preview, miri, miri-preview, reproducible-artifacts, rls, rls-preview, rust-analysis, rust-analyzer-preview, rust-docs, rust-mingw, rust-src, rust-std, rustc, rustc-dev, rustc-docs, rustfmt, rustfmt-preview
       - Host component `rust-docs` doesn't support target `aarch64-apple-darwin`
(use '--show-trace' to show detailed location information)

-> % uname -a
Darwin Nikolas-MacBook-Pro.local 20.6.0 Darwin Kernel Version 20.6.0: Mon Aug 30 06:12:20 PDT 2021; root:xnu-7195.141.6~3/RELEASE_ARM64_T8101 arm64 arm64 MacBookPro17,1 Darwin

Snip from my home manager.

{ lib, config, pkgs, ... }:

let
  oxalica-overlays = import (builtins.fetchTarball {
    url = https://github.com/oxalica/rust-overlay/archive/master.tar.gz;
  });
in
{
  nixpkgs.overlays = [ oxalica-overlays ];

  home.packages = with pkgs; [
    (rust-bin.stable.latest.default.override {
      extensions = [ "rustc" ];
      targets = [ "wasm32-unknown-unknown" ];
    })

[oxalica]

Yes. Upstream doesn't provide rust-docs for aarch64-apple-darwin currently. All available components are:
https://rust-lang.github.io/rustup-components-history/aarch64-apple-darwin.html

Upstream said it's intentional since aarch64-apple-darwin is not a tier 1 platform:
rust-lang/rustup#2692

You can install docs for only x86_64-apple-darwin as a workaround.

rust-bin.stable.latest.default.override {
  targets = [ "x86_64-apple-darwin" ];
  # Use `targetExtensions` to only install these for `targets`, not for your host platform `aarch64-apple-darwin`.
  targetExtensions = [ "rust-docs" ];
}

[npajkovsky]

That actually does not work either.

[oxalica]

That actually does not work either.

I pushed f0a3769 to fix targetExtensions. The code above should work now. Please check again on current master.
If it still doesn't work, please open a new issue.