cmd/go: reject to download toolchain when gotoolchain < go directive

[xieyuschen]

What version of Go are you using (go version)?

$ go version
go version go1.24.0 darwin/arm64

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
AR='ar'
CC='clang'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='clang++'
GCCGO='gccgo'
GO111MODULE=''
GOARCH='arm64'
GOARM64='v8.0'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/Users/yuchen.xie/Library/Caches/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/Users/yuchen.xie/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/28/7sypdf0519xfl4ylhq_90s0m0000gp/T/go-build2459204566=/tmp/go-build -gno-record-gcc-switches -fno-common'
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMOD='/dev/null'
GOMODCACHE='/Users/yuchen.xie/go/pkg/mod'
GONOPROXY='git.garena.com'
GONOSUMDB='git.garena.com'
GOOS='darwin'
GOPATH='/Users/yuchen.xie/go'
GOPRIVATE='git.garena.com'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTELEMETRY='on'
GOTELEMETRYDIR='/Users/yuchen.xie/Library/Application Support/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.24.0'
GOWORK=''
PKG_CONFIG='pkg-config'
uname -v: Darwin Kernel Version 23.4.0: Fri Mar 15 00:10:42 PDT 2024; root:xnu-10063.101.17~1/RELEASE_ARM64_T6000
ProductName:		macOS
ProductVersion:		14.4.1
BuildVersion:		23E224
lldb --version: lldb-1500.0.404.7
Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4)

What did you do?

• Case1:

mkdir verify && cd verify
go mod init m
go mod edit -go=1.26 -toolchain=go1.23.0
go version

• Case2:

mkdir verify && cd verify
go mod init m
go mod edit -go=1.24 -toolchain=go1.23.0
<my-local-path>/bin/sdk/go1.21.10/bin/go version

What did you expect to see?

Both case 1 and case 2 should be rejected, because go.mod reference said.

The suggested Go toolchain’s version cannot be less than the required Go version declared in the go directive.

Hence, before we actually downloading toolchain, we should check the version inside go.mod and report an error.
For example, go: suggested go toolchain go1.23.0 cannot be less than required go version 1.24

Besides, the case2 looks weird in real usage.

What did you see instead?

• case1:

go: downloading go1.26.0 (darwin/arm64)
go: download go1.26.0 for darwin/arm64: toolchain not available

• case 2:

go: downloading go1.24 (darwin/amd64)
go: download go1.24 for darwin/amd64: toolchain not available

[gopherbot]

Change https://go.dev/cl/653237 mentions this issue: cmd/go: validate go and toolchain versions before downloading

[gabyhelp]

Related Issues

• cmd/go: go1.22 toolchain not available #65631 (closed)
• cmd/go get doesn't validate module arguments #71437 (closed)
• cmd/go: toolchain=auto doesn't upgrade version with local replacement module #71678 (closed)
• cmd/go: download go1.22 for darwin/arm64: toolchain not available #65568 (closed)
• Should the `go` directive in `go.mod` a semver version (including patch), or not? #68971 (closed)
• cmd/go: go toolchain version switch doesn't work when only language version is set in go.mod #65580 (closed)
• cmd/go: can't invoke go in src directory #67853 (closed)
• go mod edit: changing go versions in modules to invalid versions updates go.mod and causes weird problems #66491 (closed)
• cmd/go: mod tidy reports toolchain not available with 'go 1.21' #62278 (closed)
• golang.org/x/*: go directive of 1.23.0 is forcing toolchain directives in anything not using exactly go1.23.0 #71864 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[matloob]

I'm not sure that this is necessarily incorrect behavior. The toolchain sets a minimum required version for the toolchain- it doesn't pin the toolchain at that version.

[xieyuschen]

I'm not sure that this is necessarily incorrect behavior. The toolchain sets a minimum required version for the toolchain- it doesn't pin the toolchain at that version.

HI @matloob , thanks for reply. I don't know whether it's wrong or not as well, but probably the error message 'toolchain not available' could be improved, as my CL does. The CL prints the error before it really starts to download(and fail).

In cases I mentioned above, go complains to me ''toolchain not available', and as a user I don't know what happened and how to fix it until I try to revise the toolchain to make it higher than go line.

It's quite confusing in case 2 as there is a go1.24 but why toolchain of go1.24 for darwin/amd64 is unavailable.

[samthanawalla]

For case 2, the problem is that go1.24 is a language version and not a toolchain version so when the Go Command would download go1.24 it wouldn't exist.

We fixed this in go 1.23 (#62278) to download go1.X as 1.X.0.

So hopefully that improves the confusion!

$ go1.22.0 version
go: downloading go1.24 (linux/amd64)
go: download go1.24 for linux/amd64: toolchain not available
$ go1.23.0 version
go version go1.24.0 linux/amd64