go.go

package main

import (
	"bytes"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"runtime"
	"strings"
	"text/template"
)

type OutputTemplateData struct {
	Dir  string
	OS   string
	Arch string
}

type CompileOpts struct {
	PackagePath string
	Platform    Platform
	OutputTpl   string
	Ldflags     string
	Gcflags     string
	Cc          string
	Cxx         string
	Asmflags    string
	Tags        string
	ModMode     string
	Buildmode   string
	BuildVCS    string
	Cgo         bool
	Rebuild     bool
	TrimPath    bool
	GoCmd       string
	Race        bool
}

// GoCrossCompile
func GoCrossCompile(opts *CompileOpts) error {
	env := append(os.Environ(),
		"GOOS="+opts.Platform.OS,
		"GOARCH="+opts.Platform.Arch)

	if opts.Cc != "" {
		env = append(env, "CC="+opts.Cc)
	}
	if opts.Cxx != "" {
		env = append(env, "CXX="+opts.Cxx)
	}

	// If we're building for our own platform, then enable cgo always. We
	// respect the CGO_ENABLED flag if that is explicitly set on the platform.
	if !opts.Cgo && os.Getenv("CGO_ENABLED") != "0" {
		opts.Cgo = runtime.GOOS == opts.Platform.OS &&
			runtime.GOARCH == opts.Platform.Arch
	}

	// If cgo is enabled then set that env var
	if opts.Cgo {
		env = append(env, "CGO_ENABLED=1")
	} else {
		env = append(env, "CGO_ENABLED=0")
	}

	var outputPath bytes.Buffer
	tpl, err := template.New("output").Parse(opts.OutputTpl)
	if err != nil {
		return err
	}
	tplData := OutputTemplateData{
		Dir:  filepath.Base(opts.PackagePath),
		OS:   opts.Platform.OS,
		Arch: opts.Platform.Arch,
	}
	if err := tpl.Execute(&outputPath, &tplData); err != nil {
		return err
	}

	if opts.Platform.OS == "windows" {
		outputPath.WriteString(".exe")
	}

	// Determine the full path to the output so that we can change our
	// working directory when executing go build.
	outputPathReal := outputPath.String()
	outputPathReal, err = filepath.Abs(outputPathReal)
	if err != nil {
		return err
	}

	// Go prefixes the import directory with '_' when it is outside
	// the GOPATH.For this, we just drop it since we move to that
	// directory to build.
	chdir := ""
	if opts.PackagePath[0] == '_' {
		if runtime.GOOS == "windows" {
			// We have to replace weird paths like this:
			//
			//   _/c_/Users
			//
			// With:
			//
			//   c:\Users
			//
			re := regexp.MustCompile("^/([a-zA-Z])_/")
			chdir = re.ReplaceAllString(opts.PackagePath[1:], "$1:\\")
			chdir = strings.Replace(chdir, "/", "\\", -1)
		} else {
			chdir = opts.PackagePath[1:]
		}

		opts.PackagePath = ""
	}

	args := []string{"build"}

	if opts.Rebuild {
		args = append(args, "-a")
	}

	if opts.TrimPath {
		args = append(args, "-trimpath")
	}

	if opts.ModMode != "" {
		args = append(args, "-mod", opts.ModMode)
	}

	if opts.Buildmode != "" {
		args = append(args, "-buildmode", opts.Buildmode)
	}

	if opts.BuildVCS != "" {
		args = append(args, "-buildvcs", opts.BuildVCS)
	}

	if opts.Race {
		args = append(args, "-race")
	}

	if opts.Gcflags != "" {
		args = append(args, "-gcflags", opts.Gcflags)
	}

	if opts.Ldflags != "" {
		args = append(args, "-ldflags", opts.Ldflags)
	}

	if opts.Asmflags != "" {
		args = append(args, "-asmflags", opts.Asmflags)
	}

	if opts.Tags != "" {
		args = append(args, "-tags", opts.Tags)
	}

	args = append(args, "-o", outputPathReal, opts.PackagePath)

	_, err = execGo(opts.GoCmd, env, chdir, args...)

	return err
}

// GoMainDirs returns the file paths to the packages that are "main"
// packages, from the list of packages given. The list of packages can
// include relative paths, the special "..." Go keyword, etc.
func GoMainDirs(packages []string, GoCmd string) ([]string, error) {
	args := make([]string, 0, len(packages)+3)
	args = append(args, "list", "-f", "{{.Name}}|{{.ImportPath}}")
	args = append(args, packages...)

	output, err := execGo(GoCmd, nil, "", args...)
	if err != nil {
		return nil, err
	}

	results := make([]string, 0, len(output))
	for _, line := range strings.Split(output, "\n") {
		if line == "" {
			continue
		}

		parts := strings.SplitN(line, "|", 2)
		if len(parts) != 2 {
			log.Printf("Bad line reading packages: %s", line)
			continue
		}

		if parts[0] == "main" {
			results = append(results, parts[1])
		}
	}

	return results, nil
}

// GoRoot returns the GOROOT value for the compiled `go` binary.
func GoRoot() (string, error) {
	output, err := execGo("go", nil, "", "env", "GOROOT")
	if err != nil {
		return "", err
	}

	return strings.TrimSpace(output), nil
}

// GoVersion reads the version of `go` that is on the PATH. This is done
// instead of `runtime.Version()` because it is possible to run gox against
// another Go version.
func GoVersion() (string, error) {
	// NOTE: We use `go run` instead of `go version` because the output
	// of `go version` might change whereas the source is guaranteed to run
	// for some time thanks to Go's compatibility guarantee.

	td, err := ioutil.TempDir("", "gox")
	if err != nil {
		return "", err
	}
	defer os.RemoveAll(td)

	// Write the source code for the program that will generate the version
	sourcePath := filepath.Join(td, "version.go")
	if err := ioutil.WriteFile(sourcePath, []byte(versionSource), 0644); err != nil {
		return "", err
	}

	// Execute and read the version, which will be the only thing on stdout.
	version, err := execGo("go", nil, "", "run", sourcePath)

	fmt.Printf("Detected Go Version: %s\n", version)

	return version, err
}

// GoVersionParts parses the version numbers from the version itself
// into major and minor: 1.5, 1.4, etc.
func GoVersionParts() (result [2]int, err error) {
	version, err := GoVersion()
	if err != nil {
		return
	}

	_, err = fmt.Sscanf(version, "go%d.%d", &result[0], &result[1])
	return
}

func execGo(GoCmd string, env []string, dir string, args ...string) (string, error) {
	var stderr, stdout bytes.Buffer
	cmd := exec.Command(GoCmd, args...)
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr
	if env != nil {
		cmd.Env = env
	}
	if dir != "" {
		cmd.Dir = dir
	}
	if err := cmd.Run(); err != nil {
		err = fmt.Errorf("%s\nStderr: %s", err, stderr.String())
		return "", err
	}

	return stdout.String(), nil
}

const versionSource = `package main

import (
	"fmt"
	"runtime"
)

func main() {
	fmt.Print(runtime.Version())
}`