I can take a look at implementing this if it's not prioritized. It'd be really helpful to have TryBots run before I make agopls release.

It may be a matter of configuring more than 0 builders to run for such branches, or it may require more work in coordinator; this needs investigation.

It would be helpful to figure out the reason this isn't working now. Feel free to investigate this and update the issue. Once we know what needs to be done, it'll be easier to fix this. Thanks!

I'm not very familiar with the code in cmd/coordinator.go, but my suspicion is that https://cs.opensource.google/go/build/+/master:cmd/coordinator/coordinator.go;drc=2c615328112ac3d7af87e5cf172d69f0e1bc8364;l=1205 might be the problem. From what I understand, work.Branch will be something like gopls-release-branch.0.4, while work.GoBranch will contain other branch names that never match. When goRev is empty, newBuild fails, resulting in no TryBots in the set. It seems like it works for x/ repos on master because it matches on "master".

@dmitshur: How do you suggest we fix this issue? Should x/repo branches run only with Go at tip or with previous releases as well?

@stamblerre Thanks for looking into this, that's very helpful.

What you described above sounds plausible. As a next step, let's try to confirm it. When newBuild fails, it prints a "can't create build for ..." message to the logs. We can try starting a trybot run on a "gopls-release-branch.0.4" branch, then check coordinator logs for that message.

Should x/repo branches run only with Go at tip or with previous releases as well?

The current policy explicitly mentions that it applies to "master" branch only:

// For subrepos on the "master" branch, test against prior releases of Go too.

So let's start by fixing this issue so that golang.org/x repo CLs on non-master branches are tested with Go at tip only. Afterwards, we can consider expanding it to cover prior Go releases.

It may be a matter of configuring more than 0 builders to run for such branches, or it may require more work in coordinator

I've checked the dashboard configuration, and it reports that many builders should run for this target configuration:

// +build ignore

package main

import (
	"fmt"

	"golang.org/x/build/dashboard"
)

func main() {
	// TryBuildersForProject returns the builders that should run as part of
	// a TryBot set for the given project.
	// The project argument is of the form "go", "net", "sys", etc.
	// The branch is the branch of that project ("master", "release-branch.go1.12", etc)
	// The goBranch is the branch of Go to use. If proj == "go", then branch == goBranch.
	const (
		proj     = "tools"
		branch   = "gopls-release-branch.0.4"
		goBranch = "master"
	)
	builders := dashboard.TryBuildersForProject(proj, branch, goBranch)
	for _, b := range builders {
		fmt.Println(b.Name)
	}

	// Output:
	// freebsd-amd64-12_0
	// linux-386
	// linux-amd64
	// linux-amd64-race
	// openbsd-amd64-64
	// windows-386-2008
	// windows-amd64-2016
}

Which suggests this is indeed a bug in cmd/coordinator rather than a misconfiguration in x/build/dashboard.

Yep, I saw the same thing when I tried writing a test for this. I just triggered TryBots on https://golang.org/cl/227418 - I'm not sure how to see the logs though - would you mind taking a look?

Having the tests run with tip Go sounds reasonable to me. I think I should be able to put together a CL for that.

Change https://golang.org/cl/227397 mentions this issue: cmd/coordinator: support running TryBots on x/ repo branches

I just triggered TryBots on https://golang.org/cl/227418 - I'm not sure how to see the logs though - would you mind taking a look?

Sure. I couldn't see logs far enough back for that CL, but I just sent CL 227444 while tailing logs, and saw this:

2020/04/07 21:39:01 Starting new trybot set for {tools gopls-release-branch.0.4 Idb726bed70bab8880d752f346026b66e1885425c 54a1afaa050ab8df50ca7358372cc305d184717c}
2020/04/07 21:39:01 can't create build for {"freebsd-amd64-12_0" "" "tools" "54a1afaa050ab8df50ca7358372cc305d184717c"}: required field Rev is empty; got {Name:freebsd-amd64-12_0 Rev: SubName:tools SubRev:54a1afaa050ab8df50ca7358372cc305d184717c}
2020/04/07 21:39:01 can't create build for {"linux-386" "" "tools" "54a1afaa050ab8df50ca7358372cc305d184717c"}: required field Rev is empty; got {Name:linux-386 Rev: SubName:tools SubRev:54a1afaa050ab8df50ca7358372cc305d184717c}
2020/04/07 21:39:01 can't create build for {"linux-amd64" "" "tools" "54a1afaa050ab8df50ca7358372cc305d184717c"}: required field Rev is empty; got {Name:linux-amd64 Rev: SubName:tools SubRev:54a1afaa050ab8df50ca7358372cc305d184717c}
2020/04/07 21:39:01 can't create build for {"linux-amd64-race" "" "tools" "54a1afaa050ab8df50ca7358372cc305d184717c"}: required field Rev is empty; got {Name:linux-amd64-race Rev: SubName:tools SubRev:54a1afaa050ab8df50ca7358372cc305d184717c}
2020/04/07 21:39:01 can't create build for {"openbsd-amd64-64" "" "tools" "54a1afaa050ab8df50ca7358372cc305d184717c"}: required field Rev is empty; got {Name:openbsd-amd64-64 Rev: SubName:tools SubRev:54a1afaa050ab8df50ca7358372cc305d184717c}
2020/04/07 21:39:01 can't create build for {"windows-386-2008" "" "tools" "54a1afaa050ab8df50ca7358372cc305d184717c"}: required field Rev is empty; got {Name:windows-386-2008 Rev: SubName:tools SubRev:54a1afaa050ab8df50ca7358372cc305d184717c}
2020/04/07 21:39:01 can't create build for {"windows-amd64-2016" "" "tools" "54a1afaa050ab8df50ca7358372cc305d184717c"}: required field Rev is empty; got {Name:windows-amd64-2016 Rev: SubName:tools SubRev:54a1afaa050ab8df50ca7358372cc305d184717c}

Thank you for making a CL, I'll review it next.

Change https://golang.org/cl/227537 mentions this issue: cmd/coordinator: add test for trybot release-branch.go1.N branch matching