Use .tar.gz binaries for Rust nightlies instead of .pkg

[alexchandel]

The Rust pkg installer installs as root directly to /usr/local, potentially clobbering any Homebrew files. It also doesn't install the cargo nightly binaries, which are only provided in .tar.gz form.

Rust also provides .tar.gz binaries for Mac, at http://static.rust-lang.org/dist/rust-nightly-x86_64-apple-darwin.tar.gz. These could be unarchived to /opt/homebrew-cask/Caskroom like any other cask, and symlinked into /usr/local instead. However, I'm not sure whether Cask has the machinery to symlink the contents rust/lib and rust/bin to /usr/local/lib and /usr/local/bin

Additionally, with this approach, cargo nightly binaries could also be installed. Cargo provides tarballs at http://static.rust-lang.org/cargo-dist/cargo-nightly-x86_64-apple-darwin.tar.gz.

[tapeinosyne]

Hello @alexchandel. Thanks for reporting this.

Symlinking binaries is not a problem, which means that Cargo could already be added as a cask of its own. (I think it would be the first time we included a narrow language-specific binary, which may spur some discussion.)

Adding Cargo to the Rust cask is currently impossible, as we do not yet support the installation of multiple packages from a single cask. (Implementation is ongoing in #3043, but I think the priority is fairly low.) Additionally, merging distinct upstream packages into a single cask would be an editorial decision, which we avoid.

(The specific case of Rust+Cargo is unlikely to remain problematic: Mozilla is planning to release Rust 1.0 within the year, and I trust they will provide a “batteries included” Rust+Cargo package by then.)

Switching the Rust cask from .pkg to .tar might require some persuasion, as we generally favor installers in the interest of maintenance. Are there legitimate cases where the conflict with Homebrew-installed Rust could arise? Installing from .tar would overwrite existing symlinks; would that not be an analoguous problem?

[vitorgalvao]

Closing for lack of interest/implementation. Rust 1.0 has already been released, though, so is this still an issue at all?

[alexchandel]

@vitorgalvao Actually yes (sorry for the hiatus)

Moreover, it's much easier to do now. The Rust nightlies now include cargo (see https://static.rust-lang.org/dist/rust-nightly-x86_64-apple-darwin.tar.gz and https://static.rust-lang.org/dist/rust-nightly-i686-apple-darwin.tar.gz)