os: Open("/") fails on Windows

[apmckinlay]

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

$ go version
go version go1.13.4 windows/amd64

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
set GO111MODULE=

set GOARCH=amd64

set GOBIN=

set GOCACHE=C:\Users\andrew\AppData\Local\go-build

set GOENV=C:\Users\andrew\AppData\Roaming\go\env

set GOEXE=.exe

set GOFLAGS=

set GOHOSTARCH=amd64

set GOHOSTOS=windows

set GONOPROXY=

set GONOSUMDB=

set GOOS=windows

set GOPATH=C:\Users\andrew\go

set GOPRIVATE=

set GOPROXY=https://proxy.golang.org,direct

set GOROOT=c:\go

set GOSUMDB=sum.golang.org

set GOTMPDIR=

set GOTOOLDIR=c:\go\pkg\tool\windows_amd64

What did you do?

package main

import (
	"fmt"
	"os"
)

func main() {
	_, err := os.Open("/")
	fmt.Println(err)
}

What did you expect to see?

I expected it to succeed, i.e. err == nil

What did you see instead?

It failed with:

open /: The filename, directory name, or volume label syntax is incorrect.

It works (err == nil) if you use a backslash:

os.Open(`\`)

file_windows.go openDir has:

if len(path) == 2 && path[1] == ':' || 
	(len(path) > 0 && path[len(path)-1] == '\\') { // it is a drive letter, like C:
	mask = path + `*`
} else {
	mask = path + `\*`
}

Since it only checks for trailing back slash, for forward slash "/" it adds \* resulting in /\* which is invalid.

Obviously, the workaround is to use back slash instead of forward slash. But since forward slashes work in file paths in many/most other places, it might be worth checking for either slash in openDir.

[agnivade]

Is this a new thing, or forward slashes were always supported in Windows ?

[networkimprov]

Back- and forward-slashes have long been interchangeable on Windows.

cc @alexbrainman @mattn @zx2c4
@gopherbot add OS-Windows

[alexbrainman]

@apmckinlay yes both / and \ should work in this situation.

Would you like to send a fix for this? This https://golang.org/doc/contribute.html is how to contribute.

Thank you.

Alex

[apmckinlay]

Sure, first time, but I’ll read the instructions.

…

On Tue, Nov 12, 2019 at 02:38 Alex Brainman ***@***.***> wrote: @apmckinlay <https://github.com/apmckinlay> yes both / and \ should work in this situation. Would you like to send a fix for this? This https://golang.org/doc/contribute.html is how to contribute. Thank you. Alex — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#35492?email_source=notifications&email_token=AAPRDXVGKOFGZO72ULLDON3QTJTQRA5CNFSM4JLNV22KYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEDZOPMY#issuecomment-552789939>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAPRDXSUPSQBRG644NGMBXTQTJTQRANCNFSM4JLNV22A> .

[networkimprov]

You could post to golang-dev asking if anyone would like to implement this; that's probably the quickest path to a patch...

[mattn]

Ah, I did not read this thread. I already have my changes to fix this on my local PC. @apmckinlay do you try this soon? (please feel free to answer).

[apmckinlay]

@mattn If you have a fix already prepared that's great, go ahead. (I am travelling so I would be slow)

[gopherbot]

Change https://golang.org/cl/206997 mentions this issue: os: handle backslash and slash both in the path on Windows