x/tools/gopls: panic with patch version in go.mod file

[liumingmin]

gopls version: v0.15.1 (go1.20.13)
gopls flags:
update flags: proxy
extension version: 0.39.1
go version: 1.21.6
environment: Visual Studio Code win32
initialization error: undefined
issue timestamp: Fri, 08 Mar 2024 06:09:49 GMT
restart history:
Fri, 08 Mar 2024 02:16:19 GMT: activation (enabled: true)

ATTENTION: PLEASE PROVIDE THE DETAILS REQUESTED BELOW.

Describe what you observed.

panic: invalid Go version "go1.21.6" (should be something like "go1.12")

goroutine 9724 [running]:
go/types.NewChecker(0xc000bb7950%3F, 0xc006eb10c0, 0xc008a6f360, 0x7%3F)
	  check.go:237  0x24e
golang.org/x/tools/gopls/internal/cache.(*typeCheckBatch).checkPackageForImport(0xc0091a0a20, {0x111aa38, 0xc009654180}, 0xc0021f7b00)
	  check.go:702  0x4df
golang.org/x/tools/gopls/internal/cache.(*typeCheckBatch).getImportPackage(0xc0091a0a20, {0x111aa38, 0xc009654180}, {0xc000bb7950, 0x2f})
	  check.go:469  0x767
golang.org/x/tools/gopls/internal/cache.(*Snapshot).forEachPackageInternal.func1()
	  check.go:396  0x2d
golang.org/x/sync/errgroup.(*Group).Go.func1()
	  errgroup.go:78  0x64
created by golang.org/x/sync/errgroup.(*Group).Go
	  errgroup.go:75  0xa5
[Error - 10:16:36] 

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[findleyr]

Thank you for attaching the panicking stack. We should try to fix this for our next patch release (scheduled for Monday).

[findleyr]

(I should note, this may be fixed by upgrading to Go 1.22 and reinstalling gopls).

[adonovan]

go/types at go1.20 insisted on a version string of the form "go%d.%d", and would otherwise panic. gopls (since my https://go.dev/cl/557215 in January) permits strings of the form "go%d.%d.%d" as well, since later versions of go/types use the go/version.Lang operation to sanitize/normalize.

I'll change gopls to respect the stricter semantics when compiled with go1.20. I will be so happy when we can drop support for these old toolchains.

[findleyr]

Indeed, that day can't come soon enough, particularly now that we've agreed on it!

Thanks for investigating.

[findleyr]

@liumingmin do you have an idea of why gopls was compiled with go1.20.13, while your ambient go version is 1.21.6? gopls@v0.15.1 came out last week -- have you upgraded Go in the meantime?

[adonovan]

Ah, the problem occurs only when a gopls built with go1.20 runs a go list at go1.21+. Otherwise the go1.20 list would report the go.mod file as containing a syntax error.

This is not going to fit easily into our test framework.

[findleyr]

Hmm, in general I don't think we can have forward Go command compatibility. We should probably fail loudly in this scenario.

Originally I thought this was gopls compiled with go1.21.6. Given our new understanding of this problem, I think it would be OK not to fix this for gopls@v0.15.2: gopls needs to be recompiled.