Manifesta

Introduction

The Rust programming language uses deterministic versioning for toolchain releases. Stable versions use SemVer, while nightly, beta and historical builds can be accessed by using dated builds (YY-MM-DD).

cargo-msrv is a tool which can be used to determine the minimal supported Rust version (MSRV). In cargo-msrv I started by parsing the latest channel manifest, and then decreasing the minor semver version. This is not great for many reasons:

• Except for the latest released version, we are left guessing the decreased version numbers actually exist
• Only stable versions are supported, not nightly, beta, or other channels
• Only 1.x.0 versions are supported

As a result of the above limitations, I decided to look for an actual index of releases. After doing some research I found the following options:

1. Use the AWS index (e.g. aws --no-sign-request s3 ls static-rust-lang-org/dist/ > dist.txt)
   • Rate-limited (only obtaining the index took ~40 seconds)
   • source
2. Build from individual release manifests
   • Requires parsing multiple documents
   • Approx. one week delay after a new release
   • Also has more specific toolchain information
   • source
3. Parse Rust in-repo RELEASES.md
   • Note: stable only

Each of these options requires additional parsing, which is where this crate comes in: this crate provides an index of all Rust releases. It will eventually support all three options, but initially, only the second one will be supported.

Technical options

• Bring your own download tool (planned, will be a cfg option in the future)
• Optionally, use built in download tool

Crate name

Portmanteau of "manifest", referring to the Rust release manifests this crate pulls its (meta)data from and "festa", Portuguese for party.