os: os.Stat says broken symlinks do not exist as checked by os.IsNotExist()

[quackduck]

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

$ go version
go version go1.18.3 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
GO111MODULE=""
GOARCH="arm64"
GOBIN=""
GOCACHE="/Users/ishan/Library/Caches/go-build"
GOENV="/Users/ishan/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/ishan/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/ishan/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/opt/homebrew/opt/go/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/opt/homebrew/opt/go/libexec/pkg/tool/darwin_arm64"
GOVCS=""
GOVERSION="go1.18.3"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/_d/8s653yvs3rjcnwqy_dc45wh40000gn/T/go-build2011038208=/tmp/go-build -gno-record-gcc-switches -fno-common"

To reproduce:

1. Make a file and a symlink pointing to that file
2. Delete the file
3. Check if the symlink exists according to os

I made a program that does this: https://go.dev/play/p/pCoJBeM6-rC

Code

package main

import (
	"fmt"
	"os"
)

func main() {
	_, err := os.Create("file")
	check(err)
	err = os.Symlink("file", "symlink")
	check(err)
	err = os.Remove("file")
	check(err)

	_, err = os.Stat("symlink")
	if os.IsNotExist(err) {
		fmt.Println(err) // shouldn't run, because we never deleted the symlink
	}
}

func check(err error) {
	if err != nil {
		panic(err)
	}
}

What did you expect to see?

That os says the symlink exists (even if the file it points to doesn't).

What did you see instead?

An error that the symlink does not exist.

[ZekeLu]

I think you want to use https://pkg.go.dev/os#Lstat in this case.

[quackduck]

That fixes it, but I don't see why os.Stat should say the symlink does not exist when it does exist.

[ianlancetaylor]

That's how os.Stat works: it reports information about the target of the symlink. If the target does not exist, that is what it reports. If you want information about the symlink itself, you have to use os.Lstat, as @ZekeLu suggests.

This is consistent with the C functions stat and `lstat.

Closing because there is anything to do here.

[quackduck]

Ah, thanks