Support rust-toolchain version updates specifically

[mightyiam]

What would you like Renovate to be able to do?

I'd like to have renovate itself to submit version bumps to the channel field of a rust-toolchain.toml file.

It seems that it's possible to achieve this via a feature called "regex manager" and that there's a third party shareable config that does that.

But I'd feel more comfortable with a built-in feature.

If you have any ideas on how this should be implemented, please tell us here.

Implement a built in feature for this.

Is this a feature you are interested in implementing yourself?

No

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[mirror-kt]

Good evening!
I would be very happy to see this feature implemented!

I am currently writing a project that uses a feature that is only available in nightly,
but if I simply set the channel to nightly, it will always use the latest nightly,
so yesterday's results may be different from today's results!

So it would be nice if we could fix it to a specific nightly like nightly-2023-02-18, but update it to the latest nightly once a week or so!

The version of stable can be updated by using regex of renovate,
but nightly cannot be updated by regex because the version includes the date parameter.
Native support for renovate is required.

P.S.
Information on the Rust release cycle can be found at
https://doc.rust-lang.org/book/appendix-07-nightly-rust.html

For nightly, the version number is assigned a date, since it is built and published once a day.

[rarkins]

Sounds like a new Renovate datasource may be required to get the nightly versions?

[mirror-kt]

Yeah, I think you need to add a new datasource or versioning.

Either a datasource implementation to get the latest Rust nightly version, or a versioning implementation that always compares today's date with the given version.

In the latter case, if a nightly build for today that has not yet been published is specified in rust-toolchain.toml, the previous day's build is automatically used.
This may lead to a broken build at the time today's nightly build is published.

If possible, it would be preferable to implement a datasource that compares the latest nightly build at the time it is executed, but it needs to be investigated whether Rust provides an API or other means to do this.

[AlexTMjugador]

@mirror-kt To address use cases like yours with the features available at the moment, you can let Renovate periodically update a stable Rust version through the regex manager feature described above. Then, during cargo build, set the undocumented, meant-for-internal-use RUSTC_BOOTSTRAP=1 environment variable to enable nightly features on stable toolchains. It definitely is not the prettiest or ideal solution to the problem, but it works.

An alternative, less fragile albeit more complex solution, would be to use Renovate's custom datasources and create a file with today's date as the version when it's time to upgrade. Under normal circumstances, Rust nightlies are released daily, so it's guaranteed a nightly with the date will match. Depending on your requirements, periodically updating this version file and allowing Renovate to manage the rest may be more convenient than handling the toolchain upgrades entirely outside of Renovate.

[peterhirn]

Based on the suggestion from @AlexTMjugador I hacked together a cf worker for this, see https://github.com/phi-ag/renovate-rust-nightly . 🚀

{
  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
  "extends": [
    ":semanticCommits",
    "config:best-practices",
    "group:monorepos",
    "group:recommended"
  ],
  "customDatasources": {
    "rust-nightly": {
      "defaultRegistryUrlTemplate": "https://renovate-rust-nightly.phi-ag.workers.dev/"
    }
  },
  "customManagers": [
    {
      "customType": "regex",
      "fileMatch": ["^rust-toolchain.toml$"],
      "matchStrings": ["channel = \"nightly-(?<currentValue>.+?)\"\\n"],
      "versioningTemplate": "regex:^(?<major>\\d{4})-(?<minor>\\d{2})-(?<patch>\\d{2})$",
      "datasourceTemplate": "custom.rust-nightly",
      "depNameTemplate": "rust-nightly"
    }
  ]
}

This still uses the hack where year = major, month = minor, day = patch (same problem with Minio releases). Please let me know if there is a better solution.

[kyle-leonhard]

+1 for this. It looks like https://github.com/Turbo87/renovate-config/blob/master/rust/updateToolchain.json is being used by 10s of repositories, but it'd be nice for this to be built in and just-work.

[rarkins]

Why don't you contribute it?

[kyle-leonhard]

Thanks for the reply @rarkins! I appreciate your engagement. Here's a PR: #32432