x/tools/cmd/godoc: Does not infer $GOROOT from path to binary

[fd0]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.10beta2 linux/amd64

Does this issue reproduce with the latest release?

Yes, but Go 1.10 is supposed to change that, https://tip.golang.org/doc/go1.10#goroot

(Awesome change by the way!)

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

GOARCH="amd64"
GOBIN=""
GOCACHE="/home/fd0/.cache/go-build"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/fd0/shared/work/go"
GORACE=""
GOROOT="/home/fd0/Downloads/go1.10beta2"
GOTMPDIR=""
GOTOOLDIR="/home/fd0/Downloads/go1.10beta2/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
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"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build797922256=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Without $GOROOT explicitely set, Go 1.10 infers the Go root directory from the location of the go binary as it called:

$ unset GOROOT

$ pwd
/home/fd0/Downloads/go1.10beta2

$ bin/go version
go version go1.10beta2 linux/amd64

$ bin/go env GOROOT
/home/fd0/Downloads/go1.10beta2

But this does not work for godoc:

$ bin/godoc os Exit
2018/01/15 14:17:19 cannot find package "." in:
	/src/os

$ bin/godoc -http :6060
2018/01/15 14:17:34 newDirectory(/): stat /usr/local/go: no such file or directory
2018/01/15 14:17:34 godoc: corpus fstree is nil

Explicitely setting GOROOT (like in Go < 1.10) works:

$ GOROOT=$PWD bin/godoc os Exit
use 'godoc cmd/os' for documentation on the os command 

func Exit(code int)
    Exit causes the current program to exit with the given status code.
    Conventionally, code zero indicates success, non-zero an error. The
    program terminates immediately; deferred functions are not run.

What did you expect to see?

godoc finds the Go root directory ($GOROOT) by itself, like the go binary does. This is advertised as one of the (awesome) changes of Go 1.10, apparently it does not work for godoc yet, which is unexpected.

What did you see instead?

The Go root directory is not detected automatically, I needed to set it manually via $GOROOT.

[fd0]

I spent half an hour trying to find out where godoc gets its GOROOT when none is specified (via command line -goroot or environment), but did not succeed. If someone can point me into the right direction, I'll try to prepare a PR (or whatever that's called for Gerrit).

[fd0]

Is this something that's relevant to get into 1.10? Or just "sometime"? I'm asking because I can spend some time on it this week, if it's relevant enough...

[ALTree]

go1.10 is pretty much done at this point.

Also note that the release notes say

the go tool attempts to deduce GOROOT

"the go tool" == the go binary. the godoc binary is distributed in the archives but it's another thing. So I don't think this is actually a "bug". The release notes are correct. It's just that the godoc binary does not do this specific thing that was implemented for the go binary.

[agnivade]

It seems like you have a fresh machine without a previous go installation. Because I have tried to repro your issue and it seems to work fine for me. Only when I renamed the GOROOT directory (/usr/local/go) to /usr/local/something, I can see your issue.

$unset GOROOT
$~/play/go/bin/godoc os Exit
use 'godoc cmd/os' for documentation on the os command 

func Exit(code int)
    Exit causes the current program to exit with the given status code.
    Conventionally, code zero indicates success, non-zero an error. The
    program terminates immediately; deferred functions are not run.

But, if I do -

$unset GOROOT
$sudo mv /usr/local/go /usr/local/something
$~/play/go/bin/godoc os Exit
2018/01/17 11:23:04 main.go:345: cannot find package "." in:
	/src/os

[ysmolski]

@fd0
Did you do go get -u golang.org/x/tools/cmd/godoc with your version of compiler?
I fail to reproduce this with go 1.10. Can you try the final release?

[fd0]

This issue is about the godoc binary that comes with the 1.10 release, it does not work out of the box:

$ unset GOROOT

$ sdk/go1.10/bin/go version
go version go1.10 linux/amd64

$ sdk/go1.10/bin/go env GOROOT
/home/fd0/sdk/go1.10

$ sdk/go1.10/bin/godoc strings
2018/02/19 19:41:53 cannot find package "." in:
        /src/strings

It only works when users manually set GOROOT:

$ GOROOT=sdk/go1.10 sdk/go1.10/bin/godoc strings
PACKAGE DOCUMENTATION
package strings
    import "strings"
[...]

I can build a new godoc binary with go get, and that indeed works, but this issue is about the godoc binary included with the binary releases.

I think it'd be great to make godoc work out of the box, without having to set GOROOT :)

[ysmolski]

Thanks. It seems to me that godoc is not bugged. It has built in $GOROOT path into it. Also it might be problematic to solve this bug because godoc can be installed into $GOPATH/bin and it would be not able to infer the correct path to $GOROOT.

My advise is to build godoc via get update -u if you cannot specify GOROOT for custom installed go package.

[fd0]

It seems to me that godoc is not bugged.

I think this is a bug. The godoc binary from a released version of Go behaves differently than the go binary, it requires users to manually set GOROOT before it can be used, that should be corrected. So let's agree to disagree :)

[davidpope]

I concur with @fd0 that this is undesirable behavior; whether it's a bug or feature request isn't a key distinction. Either way it certainly violates the principle of least surprise.

I never install Go in /usr/local since 1) it's just my developer tool, not something machine-wide, so why bother with 'sudo' and root access? and 2) I need to have multiple side-by-side Go versions available. I typically only add the latest one to my PATH, and I expected that this 1.10 godoc would have the same new feature that go 1.10 does for detecting GOROOT.

[ysmolski]

Obvious solution would be to copy findGOROOT from go sources to godoc. But I am not sure if this is the best one. What do you think?

modified   cmd/godoc/main.go
@@ -82,7 +82,7 @@ var (
 
 	// file system roots
 	// TODO(gri) consider the invariant that goroot always end in '/'
-	goroot = flag.String("goroot", runtime.GOROOT(), "Go root directory")
+	goroot = flag.String("goroot", findGOROOT(), "Go root directory")
 
 	// layout control
 	tabWidth       = flag.Int("tabwidth", 4, "tab width")
@@ -161,6 +161,60 @@ func initCorpus(corpus *godoc.Corpus) {
 	}
 }
 
+func findGOROOT() string {
+	if env := os.Getenv("GOROOT"); env != "" {
+		return filepath.Clean(env)
+	}
+	def := filepath.Clean(runtime.GOROOT())
+	exe, err := os.Executable()
+	if err == nil {
+		exe, err = filepath.Abs(exe)
+		if err == nil {
+			if dir := filepath.Join(exe, "../.."); isGOROOT(dir) {
+				// If def (runtime.GOROOT()) and dir are the same
+				// directory, prefer the spelling used in def.
+				if isSameDir(def, dir) {
+					return def
+				}
+				return dir
+			}
+			exe, err = filepath.EvalSymlinks(exe)
+			if err == nil {
+				if dir := filepath.Join(exe, "../.."); isGOROOT(dir) {
+					if isSameDir(def, dir) {
+						return def
+					}
+					return dir
+				}
+			}
+		}
+	}
+	return def
+}
+
+// isSameDir reports whether dir1 and dir2 are the same directory.
+func isSameDir(dir1, dir2 string) bool {
+	if dir1 == dir2 {
+		return true
+	}
+	info1, err1 := os.Stat(dir1)
+	info2, err2 := os.Stat(dir2)
+	return err1 == nil && err2 == nil && os.SameFile(info1, info2)
+}
+
+// isGOROOT reports whether path looks like a GOROOT.
+//
+// It does this by looking for the path/pkg/tool directory,
+// which is necessary for useful operation of the cmd/go tool,
+// and is not typically present in a GOPATH.
+func isGOROOT(path string) bool {
+	stat, err := os.Stat(filepath.Join(path, "pkg", "tool"))
+	if err != nil {
+		return false
+	}
+	return stat.IsDir()
+}
+