Could Rust have a left-pad incident?

The short answer: No.

What happened with left-pad?

The Node community had a lot of drama this week when a developer unpublished a package on which a lot of the world depended.

This was fundamentally possible because NPM offers an unpublish feature. Although the docs for unpublish admonish users that “It is generally considered bad behavior to remove versions of a library that others are depending on!” in large bold print, the feature is available.

What’s the Rust equivalent?

The Rust package manager, Cargo, is similar to NPM in that it helps users get the libraries on which their projects depend. Rust’s analog to the NPM index is

The best explanation of Cargo’s robustness against unpublish exploits is the docs themselves:

cargo yank

Occasions may arise where you publish a version of a crate that actually ends up being broken for one reason or another (syntax error, forgot to include a file, etc.). For situations such as this, Cargo supports a “yank” of a version of a crate.:

$ cargo yank --vers 1.0.1
$ cargo yank --vers 1.0.1 --undo

A yank does not delete any code. This feature is not intended for deleting accidentally uploaded secrets, for example. If that happens, you must reset those secrets immediately.

The semantics of a yanked version are that no new dependencies can be created against that version, but all existing dependencies continue to work. One of the major goals of is to act as a permanent archive of crates that does not change over time, and allowing deletion of a version would go against this goal. Essentially a yank means that all projects with a Cargo.lock will not break, while any future Cargo.lock files generated will not list the yanked version.

As Cargo author Alex Crichton clarified in a GitHub comment yesterday, the only way that it’s possible to remove code from is to compel the Rust tools team to edit the database and S3 bucket.

Even if a crate maintainer leaves the community in anger or legal action is taken against a crate, this workflow ensures that code deletion is only possible by a small group of people with the motivation and authority to do it in the way that’s least problematic for users of the Rust language.

For more information on the package and copyright policies, see this internals thread.

But I just want to left pad a string in Rust??

Although a left-pad crate was created as a joke, you should probably just use the format! built-in from the standard library.