go/build: move isStandardPackage to new internal/goroot package

The module code in cmd/go sometimes needs to know whether it is
looking at a standard package, and currently uses gc-specific code for
that. This CL moves the existing isStandardPackage code in the
go/build package, which works for both gc and gccgo, into a new
internal/goroot package so that cmd/go can call it. The changes to
cmd/go will be in a subsequent CL.

Change-Id: Ic1ce4c022a932c6b3e99fa062631577085cc6ecb
Reviewed-on: https://go-review.googlesource.com/137435
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/go/build/build.go

@@ -12,6 +12,7 @@ import (
 	"go/doc"
 	"go/parser"
 	"go/token"
+	"internal/goroot"
 	"io"
 	"io/ioutil"
 	"log"
@@ -656,7 +657,7 @@ func (ctxt *Context) Import(path string, srcDir string, mode ImportMode) (*Packa
 			}
 			tried.goroot = dir
 		}
-		if ctxt.Compiler == "gccgo" && isStandardPackage(path) {
+		if ctxt.Compiler == "gccgo" && goroot.IsStandardPackage(ctxt.GOROOT, ctxt.Compiler, path) {
 			p.Dir = ctxt.joinPath(ctxt.GOROOT, "src", path)
 			p.Goroot = true
 			p.Root = ctxt.GOROOT

src/go/build/deps_test.go

@@ -258,7 +258,7 @@ var pkgDeps = map[string][]string{
 	"encoding/pem":                   {"L4"},
 	"encoding/xml":                   {"L4", "encoding"},
 	"flag":                           {"L4", "OS"},
-	"go/build":                       {"L4", "OS", "GOPARSER"},
+	"go/build":                       {"L4", "OS", "GOPARSER", "internal/goroot"},
 	"html":                           {"L4"},
 	"image/draw":                     {"L4", "image/internal/imageutil"},
 	"image/gif":                      {"L4", "compress/lzw", "image/color/palette", "image/draw"},
@@ -266,6 +266,7 @@ var pkgDeps = map[string][]string{
 	"image/jpeg":                     {"L4", "image/internal/imageutil"},
 	"image/png":                      {"L4", "compress/zlib"},
 	"index/suffixarray":              {"L4", "regexp"},
+	"internal/goroot":                {"L4", "OS"},
 	"internal/singleflight":          {"sync"},
 	"internal/trace":                 {"L4", "OS"},
 	"math/big":                       {"L4"},

src/go/build/gc.go

@@ -7,131 +7,11 @@
 package build
 
 import (
-	"os"
-	"os/exec"
 	"path/filepath"
 	"runtime"
-	"strings"
-	"sync"
 )
 
 // getToolDir returns the default value of ToolDir.
 func getToolDir() string {
 	return filepath.Join(runtime.GOROOT(), "pkg/tool/"+runtime.GOOS+"_"+runtime.GOARCH)
 }
-
-// isStandardPackage is not used for the gc toolchain.
-// However, this function may be called when using `go build -compiler=gccgo`.
-func isStandardPackage(path string) bool {
-	return gccgoSearch.isStandard(path)
-}
-
-// gccgoSearch holds the gccgo search directories.
-type gccgoDirs struct {
-	once sync.Once
-	dirs []string
-}
-
-// gccgoSearch is used to check whether a gccgo package exists in the
-// standard library.
-var gccgoSearch gccgoDirs
-
-// init finds the gccgo search directories. If this fails it leaves dirs == nil.
-func (gd *gccgoDirs) init() {
-	gccgo := os.Getenv("GCCGO")
-	if gccgo == "" {
-		gccgo = "gccgo"
-	}
-	bin, err := exec.LookPath(gccgo)
-	if err != nil {
-		return
-	}
-
-	allDirs, err := exec.Command(bin, "-print-search-dirs").Output()
-	if err != nil {
-		return
-	}
-	versionB, err := exec.Command(bin, "-dumpversion").Output()
-	if err != nil {
-		return
-	}
-	version := strings.TrimSpace(string(versionB))
-	machineB, err := exec.Command(bin, "-dumpmachine").Output()
-	if err != nil {
-		return
-	}
-	machine := strings.TrimSpace(string(machineB))
-
-	dirsEntries := strings.Split(string(allDirs), "\n")
-	const prefix = "libraries: ="
-	var dirs []string
-	for _, dirEntry := range dirsEntries {
-		if strings.HasPrefix(dirEntry, prefix) {
-			dirs = filepath.SplitList(strings.TrimPrefix(dirEntry, prefix))
-			break
-		}
-	}
-	if len(dirs) == 0 {
-		return
-	}
-
-	var lastDirs []string
-	for _, dir := range dirs {
-		goDir := filepath.Join(dir, "go", version)
-		if fi, err := os.Stat(goDir); err == nil && fi.IsDir() {
-			gd.dirs = append(gd.dirs, goDir)
-			goDir = filepath.Join(goDir, machine)
-			if fi, err = os.Stat(goDir); err == nil && fi.IsDir() {
-				gd.dirs = append(gd.dirs, goDir)
-			}
-		}
-		if fi, err := os.Stat(dir); err == nil && fi.IsDir() {
-			lastDirs = append(lastDirs, dir)
-		}
-	}
-	gd.dirs = append(gd.dirs, lastDirs...)
-}
-
-// isStandard returns whether path is a standard library for gccgo.
-func (gd *gccgoDirs) isStandard(path string) bool {
-	// Quick check: if the first path component has a '.', it's not
-	// in the standard library. This skips most GOPATH directories.
-	i := strings.Index(path, "/")
-	if i < 0 {
-		i = len(path)
-	}
-	if strings.Contains(path[:i], ".") {
-		return false
-	}
-
-	if path == "unsafe" {
-		// Special case.
-		return true
-	}
-
-	gd.once.Do(gd.init)
-	if gd.dirs == nil {
-		// We couldn't find the gccgo search directories.
-		// Best guess, since the first component did not contain
-		// '.', is that this is a standard library package.
-		return true
-	}
-
-	for _, dir := range gd.dirs {
-		full := filepath.Join(dir, path)
-		pkgdir, pkg := filepath.Split(full)
-		for _, p := range [...]string{
-			full,
-			full + ".gox",
-			pkgdir + "lib" + pkg + ".so",
-			pkgdir + "lib" + pkg + ".a",
-			full + ".o",
-		} {
-			if fi, err := os.Stat(p); err == nil && !fi.IsDir() {
-				return true
-			}
-		}
-	}
-
-	return false
-}

src/go/build/gccgo.go

@@ -12,9 +12,3 @@ import "runtime"
 func getToolDir() string {
 	return envOr("GCCGOTOOLDIR", runtime.GCCGOTOOLDIR)
 }
-
-// isStandardPackage returns whether path names a standard library package.
-// This uses a list generated at build time.
-func isStandardPackage(path string) bool {
-	return stdpkg[path]
-}

src/internal/goroot/gc.go

+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build gc
+
+package goroot
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"sync"
+)
+
+// IsStandardPackage returns whether path is a standard package,
+// given goroot and compiler.
+func IsStandardPackage(goroot, compiler, path string) bool {
+	switch compiler {
+	case "gc":
+		dir := filepath.Join(goroot, "src", path)
+		_, err := os.Stat(dir)
+		return err == nil
+	case "gccgo":
+		return gccgoSearch.isStandard(path)
+	default:
+		panic("unknown compiler " + compiler)
+	}
+}
+
+// gccgoSearch holds the gccgo search directories.
+type gccgoDirs struct {
+	once sync.Once
+	dirs []string
+}
+
+// gccgoSearch is used to check whether a gccgo package exists in the
+// standard library.
+var gccgoSearch gccgoDirs
+
+// init finds the gccgo search directories. If this fails it leaves dirs == nil.
+func (gd *gccgoDirs) init() {
+	gccgo := os.Getenv("GCCGO")
+	if gccgo == "" {
+		gccgo = "gccgo"
+	}
+	bin, err := exec.LookPath(gccgo)
+	if err != nil {
+		return
+	}
+
+	allDirs, err := exec.Command(bin, "-print-search-dirs").Output()
+	if err != nil {
+		return
+	}
+	versionB, err := exec.Command(bin, "-dumpversion").Output()
+	if err != nil {
+		return
+	}
+	version := strings.TrimSpace(string(versionB))
+	machineB, err := exec.Command(bin, "-dumpmachine").Output()
+	if err != nil {
+		return
+	}
+	machine := strings.TrimSpace(string(machineB))
+
+	dirsEntries := strings.Split(string(allDirs), "\n")
+	const prefix = "libraries: ="
+	var dirs []string
+	for _, dirEntry := range dirsEntries {
+		if strings.HasPrefix(dirEntry, prefix) {
+			dirs = filepath.SplitList(strings.TrimPrefix(dirEntry, prefix))
+			break
+		}
+	}
+	if len(dirs) == 0 {
+		return
+	}
+
+	var lastDirs []string
+	for _, dir := range dirs {
+		goDir := filepath.Join(dir, "go", version)
+		if fi, err := os.Stat(goDir); err == nil && fi.IsDir() {
+			gd.dirs = append(gd.dirs, goDir)
+			goDir = filepath.Join(goDir, machine)
+			if fi, err = os.Stat(goDir); err == nil && fi.IsDir() {
+				gd.dirs = append(gd.dirs, goDir)
+			}
+		}
+		if fi, err := os.Stat(dir); err == nil && fi.IsDir() {
+			lastDirs = append(lastDirs, dir)
+		}
+	}
+	gd.dirs = append(gd.dirs, lastDirs...)
+}
+
+// isStandard returns whether path is a standard library for gccgo.
+func (gd *gccgoDirs) isStandard(path string) bool {
+	// Quick check: if the first path component has a '.', it's not
+	// in the standard library. This skips most GOPATH directories.
+	i := strings.Index(path, "/")
+	if i < 0 {
+		i = len(path)
+	}
+	if strings.Contains(path[:i], ".") {
+		return false
+	}
+
+	if path == "unsafe" {
+		// Special case.
+		return true
+	}
+
+	gd.once.Do(gd.init)
+	if gd.dirs == nil {
+		// We couldn't find the gccgo search directories.
+		// Best guess, since the first component did not contain
+		// '.', is that this is a standard library package.
+		return true
+	}
+
+	for _, dir := range gd.dirs {
+		full := filepath.Join(dir, path)
+		pkgdir, pkg := filepath.Split(full)
+		for _, p := range [...]string{
+			full,
+			full + ".gox",
+			pkgdir + "lib" + pkg + ".so",
+			pkgdir + "lib" + pkg + ".a",
+			full + ".o",
+		} {
+			if fi, err := os.Stat(p); err == nil && !fi.IsDir() {
+				return true
+			}
+		}
+	}
+
+	return false
+}

src/internal/goroot/gccgo.go

+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build gccgo
+
+package goroot
+
+import (
+	"os"
+	"path/filepath"
+)
+
+// IsStandardPackage returns whether path is a standard package,
+// given goroot and compiler.
+func IsStandardPackage(goroot, compiler, path string) bool {
+	switch compiler {
+	case "gc":
+		dir := filepath.Join(goroot, "src", path)
+		_, err := os.Stat(dir)
+		return err == nil
+	case "gccgo":
+		return stdpkg[path]
+	default:
+		panic("unknown compiler " + compiler)
+	}
+}