rustup for Go

🦀 rustup packaged as a go install-able module

//go:generate go tool cargo build

Installation

go get -tool github.com/jcbhmr/go-rustup/cmd/...@latest

Usage

go tool cargo build

Development

How it works

First, let's review the official installation guide for installing rustup:

Windows

Download and run rustup-init.exe and follow the onscreen instructions.

Linux & macOS

Run curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh in your terminal and follow the onscreen instructions.

The https://sh.rustup.rs shell script doesn't really do much; "It just does platform detection, downloads the installer and runs it." The "installer" that's being referred to can be seen in the Windows instructions: rustup-init.exe. The Linux & macOS shell script downloads a platform-specific rustup-init binary and runs it.

This rustup-init binary then reads its own argv[0] value to see that it should act like rustup. Then it copies itself to <somewhere>/rustup, <somewhere>/cargo, <somewhere>/rustc, etc. and sets up the user's PATH and a few other tidbits. Notice how it copies itself and reads its own argv[0] to see how it should act. Those rustup, cargo, rustc, etc. binaries are all the same binary code, just with different file names. The rustup-init binary is a chimara that changes its behavior based on the name of the binary.

The rustup binary is a chimera, changing its behavior based on the name of the binary. This is used most prominently to enable Rustup's tool 'proxies' - that is, rustup itself and the rustup proxies are the same binary: when the binary is called 'rustup' or 'rustup.exe' it offers the Rustup command-line interface, and when it is called 'rustc' it behaves as a proxy to 'rustc'.

This scheme is further used to distinguish the Rustup installer, called 'rustup-init', which is again just the rustup binary under a different name.

We use this fact to our advantage. We want ./cmd/rustup, ./cmd/cargo, ./cmd/rustc Go main packages that all proxy to such an appropriately named extracted & cached official rustup-init binary. But we don't actually need to include 14 different copies of the same code; we can just //go:embed one copy of the rustup-init binary and then extract & rename it to match all the expected binary names.