path/filepath: Walk reports unreadable directories twice #21758
Description
What version of Go are you using (go version)?
$ go version
go version go1.9 darwin/amd64
Does this issue reproduce with the latest release?
yes
What operating system and processor architecture are you using (go env)?
$ go env
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/pol/lm/"
GORACE=""
GOROOT="/Users/pol/go1.9"
GOTOOLDIR="/Users/pol/go1.9/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-p
refix-map=/var/folders/gg/1phmfkb169g24y_s7w7v0q_r0000gp/T/go-build230951228=/tmp/go-build -gno-record
-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
What did you do?
The following test fails:
package filepath_test
import (
"io/ioutil"
"os"
"path/filepath"
"reflect"
"testing"
)
func Test(t *testing.T) {
dir, err := ioutil.TempDir("/tmp/", "fptest")
if err != nil {
t.Fatalf("TempDir failed: %v", err)
}
crdir := filepath.Join(dir, "cant-read")
if err := os.Mkdir(crdir, 0300); err != nil {
t.Fatalf("Mkdir(%s) failed: %v", err)
}
var got []string
err = filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
got = append(got, path)
return nil
})
if err != nil {
t.Errorf("Walk(%s) failed: %v", dir, dir)
}
want := []string{dir, crdir}
if !reflect.DeepEqual(got, want) {
t.Errorf("Walk was called with paths %s; want %s", got, want)
}
}
with this output:
--- FAIL: Test (0.00s)
filepath_test.go:33: Walk was called with paths [/tmp/fptest478009460 /tmp/fptest478009460/cant-read /tmp/fptest478009460/cant-read]; want [/tmp/fptest478009460 /tmp/fptest478009460/cant-read]
That is "/tmp/fptest478009460/cant-read" (which has permissions 0300) is reported twice (once with err==nil and once with err!=nil).
This isn't reproducible on the playground: https://play.golang.org/p/ofa6fpGuVq
What did you expect to see?
Two calls to my WalkFunc:
- path==/tmp/fptest478009460 err==nil
- path==/tmp/fptest478009460/cant-read err !=nil
What did you see instead?
Three calls to my WalkFunc:
- path==/tmp/fptest478009460 err==nil
- path==/tmp/fptest478009460/cant-read err ==nil
- path==/tmp/fptest478009460/cant-read err !=nil
The result surprised me at first, but it's not entirely unreasonable. If this is intended behavior then I'd argue that at least the documentation should be updated.