cmd/gomobile: replace go/build with go/packages in gomobile-build

This is a preparation to use Go modules at gomobile command.

Updates golang/go#27234
Cherry picked from github.com/golang/mobile

Author: hajimehoshi

cmd/fyne/internal/mobile/bind.go

@@ -10,6 +10,9 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"strings"
+
+	"golang.org/x/tools/go/packages"
 )
 
 // ctx, pkg, tmpdir in build.go
@@ -61,3 +64,12 @@ func writeFile(filename string, generate func(io.Writer) error) error {
 
 	return generate(f)
 }
+
+func packagesConfig(targetOS string) *packages.Config {
+	config := &packages.Config{}
+	config.Env = append(os.Environ(), "GOARCH=arm", "GOOS="+targetOS)
+	if len(ctx.BuildTags) > 0 {
+		config.BuildFlags = []string{"-tags=" + strings.Join(ctx.BuildTags, ",")}
+	}
+	return config
+}

cmd/fyne/internal/mobile/build.go

@@ -14,8 +14,11 @@ import (
 	"io"
 	"os"
 	"os/exec"
+	"path"
 	"regexp"
 	"strings"
+
+	"golang.org/x/tools/go/packages"
 )
 
 var ctx = build.Default
@@ -77,7 +80,7 @@ func runBuild(cmd *command) (err error) {
 
 // runBuildImpl builds a package for mobiles based on the given commands.
 // runBuildImpl returns a built package information and an error if exists.
-func runBuildImpl(cmd *command) (*build.Package, error) {	cleanup, err := buildEnvInit()
+func runBuildImpl(cmd *command) (*packages.Package, error) {	cleanup, err := buildEnvInit()
 	if err != nil {
 		return nil, err
 	}
@@ -90,14 +93,13 @@ func runBuildImpl(cmd *command) (*build.Package, error) {	cleanup, err := buildE
 		return nil, fmt.Errorf(`invalid -target=%q: %v`, buildTarget, err)
 	}
 
+	// TODO(hajimehoshi): ctx is now used only for recording build tags in build. Remove this.
 	oldCtx := ctx
 	defer func() {
 		ctx = oldCtx
 	}()
-	ctx.GOARCH = targetArchs[0]
-	ctx.GOOS = targetOS
 
-	if ctx.GOOS == "darwin" {
+	if targetOS == "darwin" {
 		ctx.BuildTags = append(ctx.BuildTags, "ios")
 
 		if buildRelease {
@@ -106,19 +108,27 @@ func runBuildImpl(cmd *command) (*build.Package, error) {	cleanup, err := buildE
 		}
 	}
 
-	var pkg *build.Package
+	var buildPath string
 	switch len(args) {
 	case 0:
-		pkg, err = ctx.ImportDir(cwd, build.ImportComment)
+		buildPath = "."
 	case 1:
-		pkg, err = ctx.Import(args[0], cwd, build.ImportComment)
+		buildPath = path.Clean(args[0])
 	default:
 		cmd.usage()
 		os.Exit(1)
 	}
+	pkgs, err := packages.Load(packagesConfig(targetOS), buildPath)
 	if err != nil {
 		return nil, err
 	}
+	// len(pkgs) can be more than 1 e.g., when the specified path includes `...`.
+	if len(pkgs) != 1 {
+		cmd.usage()
+		os.Exit(1)
+	}
+
+	pkg := pkgs[0]
 
 	if pkg.Name != "main" && buildO != "" {
 		return nil, fmt.Errorf("cannot set -o when building non-main package")
@@ -133,7 +143,7 @@ func runBuildImpl(cmd *command) (*build.Package, error) {	cleanup, err := buildE
 		if pkg.Name != "main" {
 			for _, arch := range targetArchs {
 				env := androidEnv[arch]
-				if err := goBuild(pkg.ImportPath, env); err != nil {
+				if err := goBuild(pkg.PkgPath, env); err != nil {
 					return nil, err
 				}
 			}
@@ -150,7 +160,7 @@ func runBuildImpl(cmd *command) (*build.Package, error) {	cleanup, err := buildE
 		if pkg.Name != "main" {
 			for _, arch := range targetArchs {
 				env := darwinEnv[arch]
-				if err := goBuild(pkg.ImportPath, env); err != nil {
+				if err := goBuild(pkg.PkgPath, env); err != nil {
 					return nil, err
 				}
 			}
@@ -163,7 +173,7 @@ func runBuildImpl(cmd *command) (*build.Package, error) {	cleanup, err := buildE
 	}
 
 	if !nmpkgs["golang.org/x/mobile/app"] {
-		return nil, fmt.Errorf(`%s does not import "golang.org/x/mobile/app"`, pkg.ImportPath)
+		return nil, fmt.Errorf(`%s does not import "golang.org/x/mobile/app"`, pkg.PkgPath)
 	}
 
 	return pkg, nil

cmd/fyne/internal/mobile/build_androidapp.go

@@ -12,7 +12,6 @@ import (
 	"encoding/xml"
 	"errors"
 	"fmt"
-	"go/build"
 	"io"
 	"io/ioutil"
 	"log"
@@ -21,15 +20,21 @@ import (
 	"strings"
 
 	"fyne.io/fyne/cmd/fyne/internal/mobile/binres"
+	"golang.org/x/tools/go/packages"
 )
 
-func goAndroidBuild(pkg *build.Package, bundleID string, androidArchs []string, iconPath, appName string) (map[string]bool, error) {
+func goAndroidBuild(pkg *packages.Package, bundleID string, androidArchs []string, iconPath, appName string) (map[string]bool, error) {
 	ndkRoot, err := ndkRoot()
 	if err != nil {
 		return nil, err
 	}
 	libName := androidPkgName(appName)
-	manifestPath := filepath.Join(pkg.Dir, "AndroidManifest.xml")
+
+	// TODO(hajimehoshi): This works only with Go tools that assume all source files are in one directory.
+	// Fix this to work with other Go tools.
+	dir := filepath.Dir(pkg.GoFiles[0])
+
+	manifestPath := filepath.Join(dir, "AndroidManifest.xml")
 	manifestData, err := ioutil.ReadFile(manifestPath)
 	if err != nil {
 		if !os.IsNotExist(err) {
@@ -70,7 +75,7 @@ func goAndroidBuild(pkg *build.Package, bundleID string, androidArchs []string,
 			return nil, err
 		}
 		err = goBuild(
-			pkg.ImportPath,
+			pkg.PkgPath,
 			env,
 			"-buildmode=c-shared",
 			"-o", libAbsPath,
@@ -182,7 +187,7 @@ func goAndroidBuild(pkg *build.Package, bundleID string, androidArchs []string,
 		iconPath string
 	}
 	arsc.iconPath = iconPath
-	assetsDir := filepath.Join(pkg.Dir, "assets")
+	assetsDir := filepath.Join(dir, "assets")
 	assetsDirExists := true
 	fi, err := os.Stat(assetsDir)
 	if err != nil {

cmd/fyne/internal/mobile/build_iosapp.go

@@ -9,18 +9,19 @@ import (
 	"crypto/x509"
 	"encoding/pem"
 	"fmt"
-	"go/build"
 	"io/ioutil"
 	"os"
 	"os/exec"
 	"path"
 	"path/filepath"
 	"strings"
 	"text/template"
+
+	"golang.org/x/tools/go/packages"
 )
 
-func goIOSBuild(pkg *build.Package, bundleID string, archs []string, appName string) (map[string]bool, error) {
-	src := pkg.ImportPath
+func goIOSBuild(pkg *packages.Package, bundleID string, archs []string, appName string) (map[string]bool, error) {
+	src := pkg.PkgPath
 	buildO = rfc1034Label(appName) + ".app"
 
 	infoplist := new(bytes.Buffer)
@@ -108,7 +109,7 @@ func goIOSBuild(pkg *build.Package, bundleID string, archs []string, appName str
 
 	// TODO(jbd): Fallback to copying if renaming fails.
 	if buildO == "" {
-		n := pkg.ImportPath
+		n := pkg.PkgPath
 		if n == "." {
 			// use cwd name
 			cwd, err := os.Getwd()
@@ -168,13 +169,15 @@ func detectTeamID() (string, error) {
 	return cert.Subject.OrganizationalUnit[0], nil
 }
 
-func iosCopyAssets(pkg *build.Package, xcodeProjDir string) error {
+func iosCopyAssets(pkg *packages.Package, xcodeProjDir string) error {
 	dstAssets := xcodeProjDir + "/main/assets"
 	if err := mkdir(dstAssets); err != nil {
 		return err
 	}
 
-	srcAssets := filepath.Join(pkg.Dir, "assets")
+	// TODO(hajimehoshi): This works only with Go tools that assume all source files are in one directory.
+	// Fix this to work with other Go tools.
+	srcAssets := filepath.Join(filepath.Dir(pkg.GoFiles[0]), "assets")
 	fi, err := os.Stat(srcAssets)
 	if err != nil {
 		if os.IsNotExist(err) {

cmd/fyne/internal/mobile/env.go

@@ -13,7 +13,6 @@ import (
 
 // General mobile build environment. Initialized by envInit.
 var (
-	cwd          string
 	gomobilepath string // $GOPATH/pkg/gomobile
 
 	androidEnv map[string][]string // android arch -> []string
@@ -74,12 +73,6 @@ func buildEnvInit() (cleanup func(), err error) {
 }
 
 func envInit() (err error) {
-	// TODO(crawshaw): cwd only used by ctx.Import, which can take "."
-	cwd, err = os.Getwd()
-	if err != nil {
-		return err
-	}
-
 	// Setup the cross-compiler environments.
 	if ndkRoot, err := ndkRoot(); err == nil {
 		androidEnv = make(map[string][]string)