Update "toolchain" in go.mod

[rarkins]

Discussed in #24419

^{Originally posted by dornimaug September 14, 2023}

Tell us more.

Starting with Go 1.21 there is a new directive in go.mod called "toolchain", which can be used to declare the actual toolchain used to build a module in forward compatible way. See https://go.dev/blog/toolchain and https://go.dev/doc/toolchain.
This is not the same thing as the "go" directive, which Renovate already can update. But that was disabled by default in #16715 because it turned out to not be "go tools version" as originally thought but more of a compatibility statement.
The "toolchain" directive provides a way to update the go tools used to build a module transparently during the build process, without touching its compatibility statement expressed by the "go" directive or having to install any newer version of go manually in the build environment. So I think this can and even should be updated if a new version of the go tools is available and it would be useful if Renovate could perform that update.
I do not think it is able to do so now. See https://github.com/dornimaug/renovate-golang-toolchain/blob/main/go.mod#L5 for a reproducer repo.

Another discussion was started in August referencing this topic: #23824 but this ultimately was not about the "toolchain" directive at all, but the "go" directive.

Would you consider implementing toolchain updating?

[sheldonhull]

This is important as the new toolchain directive simplifies updating to newer Go versions for the building, while the compatibility version can stay the same.

The repos that have updated the latest now fail on Go updates due to this directive being invalid.

I'm using "binarySource": "docker" which has been working up till this directive.

[rarkins]

Please create a minimal reproduction demonstrating such a failed update so we can test against it

[github-actions]

Hi there,

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[kvanzuijlen]

@rarkins can you assign this issue to me?

[renovate-release]

🎉 This issue has been resolved in version 37.283.0 🎉

The release is available on:

• GitHub release
• npm package (@latest dist-tag)
• 37.283.0

Your semantic-release bot 📦🚀

[database64128]

This does not appear to work. Renovate still ignores the toolchain line and forcibly bumps the go line: database64128/tfo-go@4074a20 (https://github.com/database64128/renovate-config/blob/812dbffc3e53a061e42f47c51d6de2e8f3ef14ed/go.json). #16715 should probably be reopened as well.

[rarkins]

@database64128 please create a new discussion and minimal reproduction to demonstrate

[dornimaug]

I can confirm, that no pr or branch is created for my reproducer repository (see original post) even though renovate scans a dependency for the toolchain.
renovate-golang-toolchain.log.

According to the dashboard the update is pending: dornimaug/renovate-golang-toolchain#2

How would one enable this to actually update the toolchain?

[kvanzuijlen]

See #28465. Basically I introduced a bug when changing the depType during the PR process (and thanks for the fork I used for my reproduction repository 😀)

[database64128]

@rarkins Opened #28468

[dornimaug]

See #28465. Basically I introduced a bug when changing the depType during the PR process (and thanks for the fork I used for my reproduction repository 😀)

I can now can confirm that everything is working as expected: dornimaug/renovate-golang-toolchain#3

Thank you for implementing this feature.

[kvanzuijlen]

Thanks @rarkins for having a fix ready this quickly! ❤️