embed: FS.Open not compatible with os.Open

[acynothia]

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

$ go version
go version go1.16.5 linux/amd64

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="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOENV="/root/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/root/.go/pkg/mod"
GONOPROXY="gitlab.papegames.com,gitee.com"
GONOSUMDB="gitlab.papegames.com,gitee.com"
GOOS="linux"
GOPATH="/root/.go:/root/go"
GOPRIVATE=""
GOPROXY="https://goproxy.cn,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16.5"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/root/go/src/test/testdir/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2652719403=/tmp/go-build -gno-record-gcc-switches"

What did you do?

package main

import (
    "embed"
    "fmt"
    "os"
)

//go:embed test
var staticFS embed.FS

func main() {
    fmt.Println(os.Open("./test"))
    fmt.Println("----")
    fmt.Println(os.Open("./test/"))
    fmt.Println("----")
    fmt.Println(staticFS.Open("test"))
    fmt.Println("----")
    fmt.Println(staticFS.Open("test/"))
}

What did you expect to see?

the same as fmt.Println(staticFS.Open("test"))

What did you see instead?

&{0xc00004e180} <nil>
----
&{0xc00004e1e0} <nil>
----
&{0x4eab98 [{test/a str1
 [63 163 252 108 86 4 30 104 91 211 217 230 175 19 117 126]} {test/b str2
 [157 163 134 109 137 33 72 250 70 235 54 167 230 171 44 117]}] 0} <nil>
----
<nil> open test/: file does not exist

It cause http.FS can not found index.html, because dir always end with /

[seankhliao]

This works as intended, fs.FS implementations should validate paths with https://pkg.go.dev/io/fs#ValidPath which rejects trailing slashes. If you want to serve index.html then you need to rewrite/redirect the request, see what http.FileServer does.

Closing as this works as intended

[acynothia]

This works as intended, fs.FS implementations should validate paths with https://pkg.go.dev/io/fs#ValidPath which rejects trailing slashes. If you want to serve index.html then you need to rewrite/redirect the request, see what http.FileServer does.

Thanks for your explanation. If fs.FS implementations should validate paths, can we trim slashes in http.FS https://github.com/golang/go/blob/master/src/net/http/fs.go#L758 ?

For now. http.Handle("/", http.FileServer(http.FS(fsys))) with embed.FS can only work in root path because of specified dotFile make it work.