os,syscall: implement functions related to uid, gid and pid on js/wasm

This change implements the following functions on js/wasm:
- os.Chown
- os.Fchown
- os.Lchown
- syscall.Getuid
- syscall.Getgid
- syscall.Geteuid
- syscall.Getegid
- syscall.Getgroups
- syscall.Getpid
- syscall.Getppid
- syscall.Umask

Change-Id: Icdb0fafc02c9df6e9e3573542f8499c3464dc671
Reviewed-on: https://go-review.googlesource.com/c/go/+/154157
Run-TryBot: Richard Musiol <neelance@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/go/internal/work/build_test.go

@@ -227,8 +227,8 @@ func TestRespectSetgidDir(t *testing.T) {
 		if runtime.GOARCH == "arm" || runtime.GOARCH == "arm64" {
 			t.Skip("can't set SetGID bit with chmod on iOS")
 		}
-	case "windows", "plan9", "js":
-		t.Skip("chown/chmod setgid are not supported on Windows, Plan 9, or JS")
+	case "windows", "plan9":
+		t.Skip("chown/chmod setgid are not supported on Windows or Plan 9")
 	}
 
 	var b Builder

src/os/os_unix_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
+// +build aix darwin dragonfly freebsd js,wasm linux netbsd openbsd solaris
 
 package os_test
 
@@ -152,6 +152,9 @@ func TestLchown(t *testing.T) {
 	gid := Getgid()
 	t.Log("gid:", gid)
 	if err = Lchown(linkname, -1, gid); err != nil {
+		if err, ok := err.(*PathError); ok && err.Err == syscall.ENOSYS {
+			t.Skip("lchown is unavailable")
+		}
 		t.Fatalf("lchown %s -1 %d: %s", linkname, gid, err)
 	}
 	sys := dir.Sys().(*syscall.Stat_t)
@@ -231,6 +234,10 @@ func TestMkdirStickyUmask(t *testing.T) {
 
 // See also issues: 22939, 24331
 func newFileTest(t *testing.T, blocking bool) {
+	if runtime.GOOS == "js" {
+		t.Skipf("syscall.Pipe is not available on %s.", runtime.GOOS)
+	}
+
 	p := make([]int, 2)
 	if err := syscall.Pipe(p); err != nil {
 		t.Fatalf("pipe: %v", err)

src/os/sticky_bsd.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build aix darwin dragonfly freebsd netbsd openbsd solaris
+// +build aix darwin dragonfly freebsd js,wasm netbsd openbsd solaris
 
 package os
 

src/os/sticky_notbsd.go

@@ -6,6 +6,7 @@
 // +build !darwin
 // +build !dragonfly
 // +build !freebsd
+// +build !js !wasm
 // +build !netbsd
 // +build !openbsd
 // +build !solaris

src/syscall/fs_js.go

@@ -244,18 +244,26 @@ func Chown(path string, uid, gid int) error {
 	if err := checkPath(path); err != nil {
 		return err
 	}
-	return ENOSYS
+	_, err := fsCall("chown", path, uint32(uid), uint32(gid))
+	return err
 }
 
 func Fchown(fd int, uid, gid int) error {
-	return ENOSYS
+	_, err := fsCall("fchown", fd, uint32(uid), uint32(gid))
+	return err
 }
 
 func Lchown(path string, uid, gid int) error {
 	if err := checkPath(path); err != nil {
 		return err
 	}
-	return ENOSYS
+	if jsFS.Get("lchown") == js.Undefined() {
+		// fs.lchown is unavailable on Linux until Node.js 10.6.0
+		// TODO(neelance): remove when we require at least this Node.js version
+		return ENOSYS
+	}
+	_, err := fsCall("lchown", path, uint32(uid), uint32(gid))
+	return err
 }
 
 func UtimesNano(path string, ts []Timespec) error {

src/syscall/syscall_js.go

@@ -285,14 +285,45 @@ func Getwd() (wd string, err error) {
 	return string(buf[:n]), nil
 }
 
-func Getegid() int                      { return 1 }
-func Geteuid() int                      { return 1 }
-func Getgid() int                       { return 1 }
-func Getgroups() ([]int, error)         { return []int{1}, nil }
-func Getppid() int                      { return 2 }
-func Getpid() int                       { return 3 }
-func Gettimeofday(tv *Timeval) error    { return ENOSYS }
-func Getuid() int                       { return 1 }
+func Getuid() int {
+	return jsProcess.Call("getuid").Int()
+}
+
+func Getgid() int {
+	return jsProcess.Call("getgid").Int()
+}
+
+func Geteuid() int {
+	return jsProcess.Call("geteuid").Int()
+}
+
+func Getegid() int {
+	return jsProcess.Call("getegid").Int()
+}
+
+func Getgroups() ([]int, error) {
+	array := jsProcess.Call("getgroups")
+	groups := make([]int, array.Length())
+	for i := range groups {
+		groups[i] = array.Index(i).Int()
+	}
+	return groups, nil
+}
+
+func Getpid() int {
+	return jsProcess.Get("pid").Int()
+}
+
+func Getppid() int {
+	return jsProcess.Get("ppid").Int()
+}
+
+func Umask(mask int) (oldmask int) {
+	return jsProcess.Call("umask", mask).Int()
+}
+
+func Gettimeofday(tv *Timeval) error { return ENOSYS }
+
 func Kill(pid int, signum Signal) error { return ENOSYS }
 func Sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) {
 	return 0, ENOSYS