cmd/go: go test does not utilize -p setting without prior go build

[dpanic]

Go version

go version go1.23.5 linux/amd64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='amd64'
GOBIN='/home/user/go/bin'
GOCACHE='/home/user/.cache/go-build'
GOENV='/home/user/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/user/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/user/go'
GOPRIVATE=''
GOPROXY='http://gitlab.lan:3000,https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.23.5'
GODEBUG='madvdontneed=1'
GOTELEMETRY='local'
GOTELEMETRYDIR='/home/user/.config/go/telemetry'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/home/user/projects/1681377694/worker/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build142279062=/tmp/go-build -gno-record-gcc-switches'

What did you do?

I executed the following command to run tests without running go build first:

timeout -s KILL 32m xvfb-run -a --server-args="-screen 0 1600x900x24 -noreset" go test -v -json -parallel=1 -p=14 -timeout=2m -count=1 ./... >$REPORT_FILE 2>&1 || true

However, when I include go build before the test command, like this:
go build && timeout -s KILL 32m xvfb-run -a --server-args="-screen 0 1600x900x24 -noreset" go test -v -json -parallel=1 -p=14 -timeout=2m -count=1 ./... >$REPORT_FILE 2>&1 || true

the tests utilize all 14 parallel packages as expected.###

What did you see happen?

When running go test without go build, a maximum of only 2 parallel packages are executed, despite setting -p=14.

What did you expect to see?

I expected go test to utilize 14 parallel packages as specified with -p=14, even without running go build beforehand.

[seankhliao]

I think we need to see a full reproducer (including the packages it tries to build).
Are the extra command runners necessary to reproduce the issue?

[gabyhelp]

Related Issues

• cmd/go: test Documentation: Package List Parallelisation #36741
• proposal: cmd/go: add an option to sequentially run tests #61318
• cmd/go: go test -parallel=1 (disable parallel tests?) output is confusing #18118 (closed)
• cmd/go: `go test -c` does not accept `-o $dir` #58162 (closed)
• cmd/go/internal/test: default pgo=auto results in surprising slow behaviour #61983
• cmd/go: docs are unclear that tests are run in parallel across packages #11521 (closed)
• cmd/go: go test -v does not stream logs when testing multiple packages #46959
• cmd/go: go test -help doesn't show test flags in Go 1.12 #30365 (closed)
• cmd/go: invalid values for go build flag -p don't fail builds #46686 (closed)
• go test broken with parameters #33869 (closed)

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