x/website: TestAPIVersion test fails when GOROOT is the toolchain module

[hyangah]

$ go env -changed
GOTOOLCHAIN='go1.26.1+auto'
$ go version
go version go1.26.1 linux/amd64

--- FAIL: TestAPIVersion (0.00s)
    api_test.go:138: sinceFunc("archive/tar", "func", "", "FileInfoHeader") = ""; want "1.1"
    api_test.go:138: sinceFunc("bufio", "type", "", "Scanner") = ""; want "1.1"
    api_test.go:138: sinceFunc("bufio", "method", "*Reader", "WriteTo") = ""; want "1.1"
    api_test.go:138: sinceFunc("bytes", "func", "", "LastIndexByte") = ""; want "1.5"
    api_test.go:138: sinceFunc("crypto", "type", "", "Decrypter") = ""; want "1.5"
    api_test.go:138: sinceFunc("crypto/rsa", "method", "*PrivateKey", "Decrypt") = ""; want "1.5"
    api_test.go:138: sinceFunc("debug/dwarf", "method", "Class", "GoString") = ""; want "1.5"
    api_test.go:138: sinceFunc("os", "func", "", "IsTimeout") = ""; want "1.10"
    api_test.go:138: sinceFunc("strings", "type", "", "Builder") = ""; want "1.10"
    api_test.go:138: sinceFunc("strings", "method", "*Builder", "WriteString") = ""; want "1.10"
    api_test.go:138: sinceFunc("os", "method", "*File", "ReadDir") = ""; want "1.16"

The test failure is caused by a missing dependency on the Go installation's api directory.

1. What the test does: TestAPIVersion calls api.Load(os.DirFS(runtime.GOROOT())) to read files matching api/go*.txt (e.g., go1.1.txt , go1.2.txt , etc.) from the Go root directory. These files contain the list of symbols added in each Go version.

2. Where it searches: In your current environment, runtime.GOROOT() points to:
   GOMODCACHE/pkg/mod/golang.org/toolchain@v0.0.1-go1.26.1.linux-amd64

3. The problem: This directory is a downloaded toolchain and does not contain the api directory.

The tests run by GCB and prod service with _goroot.zip, so they don't have this issue.
How about we skip this test if the api files aren't exist AND GOLANGORG_FORCE_GOROOT_ZIP isn't set?

[gabyhelp]

Related Issues

• cmd/go: TestScript/gotoolchain_path fails if golang.org/dl/go1.21.1 is installed in the user's $PATH #62709 (closed)
• x/tools/internal/gcimporter: TestImportTypeparamTests depends on `GOROOT/test/typeparam` #70081 (closed)
• x/tools/gopls: integration testing may not test cases with old go versions #69630 (closed)

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

[jba]

Can you explain what GOLANGORG_FORCE_GOROOT_ZIP does? The only reference to it I can find is this issue. (If you're just introducing it to override this skip, then is it really needed?)