net/http: perhaps merge IsDir checks in fs.go

[spacewander]

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

$ go version
go version go1.12.6 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
~ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/vagrant/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/vagrant/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
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-build301219300=/tmp/go-build -gno-record-gcc-switches"

What did you see instead?

In net/http/tranfers.go: https://github.com/golang/go/blob/master/src/net/http/transfer.go#L254

        if t.ContentLength > 0 {
		return true
	}
	if t.ContentLength < 0 {
		return false
	}
	// Many servers expect a Content-Length for these methods
	if t.Method == "POST" || t.Method == "PUT" {
		return true
	}
	if t.ContentLength == 0 && isIdentity(t.TransferEncoding) {

Since we have already checked t.ContentLength > 0 and t.ContentLength < 0, the t.ContentLength == 0 in the fourth if branch looks useless.

---

In net/http/fs.go: https://github.com/golang/go/blob/master/src/net/http/fs.go#L586

	if d.IsDir() {
		url := r.URL.Path
		if url[len(url)-1] != '/' {
			localRedirect(w, r, path.Base(url)+"/")
			return
		}
	}

	// use contents of index.html for directory, if present
	if d.IsDir() {
		index := strings.TrimSuffix(name, "/") + indexPage
		ff, err := fs.Open(index)
		if err == nil {
			defer ff.Close()
			dd, err := ff.Stat()
			if err == nil {
				name = index
				d = dd
				f = ff
			}
		}
	}

Maybe we could merge this two if d.IsDir() { into one.

Please correct me if I am wrong.

[andybons]

In the first example, the check may seem useless but it’s explicit, which can be more clear to people when reading the code. I don’t think opening a change for that is necessary.

The second example seems more appropriate to fix since it’s checking d.IsDir() three times in a row.

[bharaththiruveedula-zz]

@andybons , can I work on this?

[spacewander]

@andybons
I am not sure if the three IsDir checks can be merged into one, because the d maybe be changed in the second IsDir block. And /path/to/index.html might be a directory which can be opened successfully. Maybe we should merge them into two.

I will give some time this weekend to submit a patch if a PR is welcome.

[andybons]

@bharaththiruveedula @spacewander I will leave it up to both of you to determine who will author a patch.

Keep in mind we're still in the 1.13 freeze right now so the changes won't actually be merged until the 1.14 tree opens.

[spacewander]

@andybons
Just submit a PR with a few lines.

[gopherbot]

Change https://golang.org/cl/188677 mentions this issue: net/http: merge IsDir checks in fs.go's serveFile function

[bharaththiruveedula-zz]

@spacewander please follow first come first serve and wait if no activity is there. Please don't override anyone here. Anyways it's fine. Hope we follow some rules in the community!

[andybons]

@bharaththiruveedula as @spacewander filed the issue, it’s fair for them to contribute the change to fix it. There are plenty of other issues to help with.