Could rust become keg-only and rustup become a normal formula?

[ilyagr]

Output of brew config

HOMEBREW_VERSION: 4.4.19
ORIGIN: https://github.com/Homebrew/brew
HEAD: 23facb219df8615680636ef12103bb3313f44e2a
Last commit: 4 days ago
Branch: stable
Core tap JSON: 31 Jan 21:55 UTC
Core cask tap JSON: 31 Jan 21:55 UTC
HOMEBREW_PREFIX: /opt/homebrew
HOMEBREW_CASK_OPTS: []
HOMEBREW_DISPLAY: /private/tmp/com.apple.launchd.eVl4su3i9k/org.xquartz:0
HOMEBREW_EDITOR: vim
HOMEBREW_MAKE_JOBS: 12
HOMEBREW_NO_CLEANUP_FORMULAE: fish
Homebrew Ruby: 3.3.7 => /opt/homebrew/Library/Homebrew/vendor/portable-ruby/3.3.7/bin/ruby
CPU: dodeca-core 64-bit arm_blizzard_avalanche
Clang: 16.0.0 build 1600
Git: 2.48.1 => /opt/homebrew/bin/git
Curl: 8.7.1 => /usr/bin/curl
macOS: 14.7.3-arm64
CLT: 16.2.0.0.1.1733547573
Xcode: 16.2
Rosetta 2: false

Description of issue

I have two related problems:

• When I do brew install --HEAD fish, it installs rust as a dependency as expected. However, this means that running cargo then runs Homebrew's Rust instead of the one I've installed myself via Rustup. I have to remember to run brew unlink rust every time to fix it.
• It's inconvenient for me to use the rustup formula since it's keg-only and requires updating the PATH. I end up using manually installed rustup.

I don't know if this qualifies as a bug, but both problems would be solved if the rust formula became keg-only (since it seems most appropriately used as a built-time dependency for other formulas) and rustup became a normal formula (since it's more useful for a Rust developer who will manually call these binaries).

Is there any chance that this change could happen?

[SMillerDev]

I think that would complicate the use case where some new user thinks "I want to install rust" a lot.
Because after this change that would mean they don't have a usable rust version.

I'd be opposed to this change for that reason, it is simplifying the workflow of knowledgeable users and complicating the workflow of new ones.

[ilyagr]

I agree that this is an important consideration. I'm not sure what rustup's behavior is if no toolchain is installed. The formula does print a hint to run rustup toolchain install stable; I'm hoping that any sort of cargo command would also either install a toolchain or at least print a hint if there is no toolchain installed.

I'm also not sure the current situation is good for new users, since so many of Rust docs out there assume rustup-installed Rust. New users could get very confused if the instructions for contributing to a project require running cargo +nightly fmt, and that results in a confusing error because the cargo isn't actually called via rustup and doesn't understand +nightly.

[ilyagr]

I can also put it this way: when I'm telling people how to install Rust in, say, contributing guidelines for a project, I would currently say "please use the official installer and never, ever think of using a package manager". This is because many projects require cargo +nightly fmt, and some fully rely on nightly features. If I mentioned Homebrew at all, it would be to warn people that if something weird is going on, they should try brew unlink rust.

If this change was made, I could tell them "you can use the official installer, or just do brew install rustup if that's easier".

At least, that would be the goal; on second thought, somebody would have to check how well the resulting setup works (say, whether ~/.cargo/bin ends up in the path, or whether cargo install installs things somewhere else).

[micolous]

The other reason for why a Rust package maintainer says “never ever install your package manager’s version of Rust” is that it is quite often extremely out of date, and the Rust ecosystem tends to move fairly quickly, so it only supports a handful of older versions (“MSRV”).

As an example, at the time of writing, 1.86 is the current upstream stable version, but Debian stable (bookworm) ships with 1.63, which won’t even build a lot of Rust software anymore.

[SMillerDev]

Just curious, wouldn't it be easy for you to just add this to your shell init script:

export PATH="$(brew --prefix)/opt/rustup/bin:#PATH"

[micolous]

As another argument for making Homebrew Rust keg-only: Homebrew’s package includes a toolchain for the host OS/architecture only.

If you cross-compile software for other architectures, then that’s no good.

If you build web applications in Rust, then you’re cross-compiling to WASM.

If you build firmware for embedded devices in Rust, then you’re cross-compiling for that… and probably running a specific nightly build.

The alternative is if there was a way to tell Homebrew to always unlink certain packages.