Golang testing: TempDir fails when TMPDIR is a relative directory and os.Chdir() is called

Go version

1.22.4

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='amd64'
GOBIN='/home/martin/.local/gobin'
GOCACHE='/home/martin/.cache/go/cache'
GOENV='/home/martin/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS='-modcacherw'
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/martin/.cache/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/martin/.cache/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/lib/go'
GOSUMDB='sum.golang.org'
GOTMPDIR='/home/martin/.cache/go/tmp'
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/lib/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.22.4'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='cc'
CXX='c++'
CGO_ENABLED='1'
GOMOD='/home/martin/testtmp/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 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/home/martin/.cache/go/tmp/go-build3133883126=/tmp/go-build -gno-record-gcc-switches'

---

Setup:

% mkdir tmp
% go mod init testtemp

% cat test_test.go
package main

import (
    "fmt"
    "os"
    "testing"
)

func TestTest(t *testing.T) {
    fmt.Println(t.TempDir())
    fmt.Println(t.TempDir())
    os.Chdir("./tmp")
    fmt.Println(t.TempDir())
}

This runs fine:

% go test
/tmp/TestTest731866446/001
/tmp/TestTest731866446/002
/tmp/TestTest731866446/003

But when setting TMPDIR to ./tmp it stops working after the os.Chdir() call:

% TMPDIR=./tmp go test
./tmp/TestTest4094023708/001
./tmp/TestTest4094023708/002
--- FAIL: TestTest (0.00s)
    test_test.go:13: TempDir: stat ./tmp: no such file or directory
FAIL
exit status 1
FAIL    test    0.002s

It needs to be the full path:

% TMPDIR=/home/martin/testtmp/tmp go test
/home/martin/testtmp/tmp/TestTest2010017600/001
/home/martin/testtmp/tmp/TestTest2010017600/002
/home/martin/testtmp/tmp/TestTest2010017600/003
PASS
ok      test    0.002s

---

Context: I have some filesystem-specific code that's sensitive to the current directory, so I need to change it. I have ./tmp mounted as a XFS image to test that it works on that, in addition to ext4.

I can just use the full path of course, but it's fairly long and annoying, and "it works fine, except in this one specific case" is rather confusing. And should be easy enough to fix with filepath.Abs() call.

Comment From: gabyhelp

Similar Issues

• https://github.com/golang/go/issues/23264
• https://github.com/golang/go/issues/19695
• https://github.com/golang/go/issues/40853
• https://github.com/golang/go/issues/50644
• https://github.com/golang/go/issues/61585

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

Comment From: seankhliao

I'd say this is working as intended. You want TMPDIR to be relative to the current directory, and it stays relative to your working directory.

TMPDIR=$(pwd)/tmp isn't that much to type out.