Linking to docs.rs/<crate>/ when crate version is latest

[jsha]

In rust-lang/docs.rs#1438 I'm working on improving ability for search engines to reliably find the latest version of a crate. The main part of the docs.rs work is done: https://docs.rs/rustls/ now redirects to https://docs.rs/rustls/latest/rustls/, not https://docs.rs/rustls/0.20.2/rustls/.

It would be helpful if crates.io also linked to the latest version. In particular, I'm proposing: If a user is viewing the latest version of crate, the documentation link on crates.io should point to https://docs.rs/<cratename>/ instead of a specific versioned URL. If the user is viewing an older version, the documentation link on crates.io should continue to point to a versioned URL as it does today.

[Turbo87]

hmm, I think that would only work if both systems used the exact same algorithm to determine what the latest version is 🤔

[syphar]

hmm, I think that would only work if both systems used the exact same algorithm to determine what the latest version is 🤔

How does crates.io do this? Could you point us to the place in the code?

In docs.rs it does not depend on the build-status:

https://github.com/rust-lang/docs.rs/blob/6e354ec15c6652660afd8a071b3d09b3b8eb6b68/src/web/crate_details.rs#L229-L234

[Turbo87]

crates.io/app/models/crate.js

Lines 30 to 43 in 56301b6

	/**
	* This is the default version that will be shown when visiting the crate
	* details page. Note that this can be `undefined` if all versions of the crate
	* have been yanked.
	* @return {string}
	*/
	get defaultVersion() {
	if (this.max_stable_version) {
	return this.max_stable_version;
	}
	if (this.max_version && this.max_version !== '0.0.0') {
	return this.max_version;
	}
	}

and

crates.io/app/routes/crate/version.js

Lines 30 to 31 in 56301b6

	let { defaultVersion } = crate;
	version = versions.find(version => version.num === defaultVersion) ?? versions.lastObject;

are the relevant code locations, but that's not necessarily stable.

I've been thinking about exposing something like default_version on the API which would be calculated by the backend. We are currently exposing max_stable_version and max_version, but both of them don't take yanked crates into account and it puts the responsibility on the API client to figure out what the default should be.

[syphar]

Hm... on top of that:

Depending on the build-prioritization it can sometimes take 12 hours for the build to happen.

So the only way that /latest/ always points to the correct, exact version would be docs.rs reporting back build-status to crates.io.