Golang os: ReadDir on regular file returns non nil slice on Windows

Go version

go version go1.25.0 windows/amd64

Output of go env in your module/workspace:

AR=ar
CC=gcc
CGO_CFLAGS=-O2 -g
CGO_CPPFLAGS=
CGO_CXXFLAGS=-O2 -g
CGO_ENABLED=1
CGO_FFLAGS=-O2 -g
CGO_LDFLAGS=-O2 -g
CXX=g++
GCCGO=gccgo
GO111MODULE=
GOAMD64=v1
GOARCH=amd64
GOAUTH=netrc
GOBIN=
GOCACHE=C:\Users\runneradmin\AppData\Local\go-build
GOCACHEPROG=
GODEBUG=
GOENV=C:\Users\runneradmin\AppData\Roaming\go\env
GOEXE=.exe
GOEXPERIMENT=
GOFIPS140=off
GOFLAGS=
GOGCCFLAGS=-m64 -mthreads -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=C:\Users\RUNNER~1\AppData\Local\Temp\go-build2877138821=/tmp/go-build -gno-record-gcc-switches
GOHOSTARCH=amd64
GOHOSTOS=windows
GOINSECURE=
GOMOD=D:\a\tracktools\tracktools\go.mod
GOMODCACHE=C:\Users\runneradmin\go\pkg\mod
GONOPROXY=
GONOSUMDB=
GOOS=windows
GOPATH=C:\Users\runneradmin\go
GOPRIVATE=
GOPROXY=https://proxy.golang.org,direct
GOROOT=C:\hostedtoolcache\windows\go\1.25.0\x64
GOSUMDB=sum.golang.org
GOTELEMETRY=local
GOTELEMETRYDIR=C:\Users\runneradmin\AppData\Roaming\go\telemetry
GOTMPDIR=
GOTOOLCHAIN=auto
GOTOOLDIR=C:\hostedtoolcache\windows\go\1.25.0\x64\pkg\tool\windows_amd64
GOVCS=
GOVERSION=go1.25.0
GOWORK=
PKG_CONFIG=pkg-config

What did you do?

Call os.ReadDir on a file entry, Linux and Mac both return nil, syscall.ENOTDIR but Windows returns []fs.DirEntry{}, syscall.ENOTDIR.

In previous versions of go (v1.22) all platforms returned []fs.DirEntry{}, syscall.ENOTDIR

package main

import (
    "io/fs"
    "os"
    "syscall"
    "testing"
    "time"

    "github.com/stretchr/testify/require"
)

func Test_ReadDir(t *testing.T) {
    tf, err := os.CreateTemp(t.TempDir(), "os-test")
    require.NoError(t, err)

    name := tf.Name()
    require.NoError(t, tf.Close())

    dirs, err := os.ReadDir(name)
    require.ErrorIs(t, err, syscall.ENOTDIR)
    var expectedDirs []fs.DirEntry
    require.Equal(t, expectedDirs, dirs)
}

Result is:

    osfs_test.go:23: 
            Error Trace:    osfs_test.go:23
            Error:          Not equal: 
                            expected: []fs.DirEntry(nil)
                            actual  : []fs.DirEntry{}

                            Diff:
                            --- Expected
                            +++ Actual
                            @@ -1,2 +1,3 @@
                            -([]fs.DirEntry) <nil>
                            +([]fs.DirEntry) {
                            +}

            Test:           Test_ReadDir

What did you see happen?

Windows returned []fs.DirEntry{}, syscall.ENOTDIR

What did you expect to see?

Consistent behaviour between all operating systems, Linux and Mac both return nil, syscall.ENOTDIR but Windows returns []fs.DirEntry{}, syscall.ENOTDIR.

Comment From: gabyhelp

Related Issues

• os: ReadDir on regular file returns ERROR_PATH_NOT_FOUND instead of ENOTDIR #46734
• os: ReadFile on directories does not return EISDIR in windows #43322
• os: `ReadDir` fails on file systems without File ID support on Windows #61907 (closed)
• os: ReadDir(`\.\pipe\`) fails with go1.21 on Windows #61918 (closed)
• io/fs,os: fs.ReadDir with an os.DirFS can produce invalid paths #44166 (closed)
• os: os.DirFS doesn't work with Windows UNC paths #54694 (closed)
• os: ReadDir("\tsclient\d\") fails with go1.21 on Windows #62044 (closed)
• os: document that fs.ReadDirFile.ReadDir doesn't restart each time #69301 (closed)
• os: Stat() returns inconsistent error on Windows #29119 (closed)

Related Code Changes

• os: return EISDIR when ReadFile is attempted on a directory on windows

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

Comment From: cherrymui

cc @golang/windows

Comment From: qmuntal

Thanks for reporting, fix incoming.

Comment From: gopherbot

Change https://go.dev/cl/699375 mentions this issue: os: return nil slice when ReadDir is used with a file on file_windows