gopy: proper handling of lang option

This CL introduces a split in handling of {py|py2|py3}{thon,}.
It also lifts up the bind.Package creation so the processing is done only once.

Change-Id: I946605fb24885df986baa77088f76df90ff4d168

cmd_bind.go

@@ -6,7 +6,6 @@ package main
 
 import (
 	"fmt"
-	"go/build"
 	"io/ioutil"
 	"log"
 	"os"
@@ -32,6 +31,7 @@ ex:
 		Flag: *flag.NewFlagSet("gopy-bind", flag.ExitOnError),
 	}
 
+	cmd.Flag.String("lang", "py2", "python version to use for bindings (python2|py2|python3|py3)")
 	cmd.Flag.String("output", "", "output directory for bindings")
 	return cmd
 }
@@ -47,6 +47,7 @@ func gopyRunCmdBind(cmdr *commander.Command, args []string) error {
 	}
 
 	odir := cmdr.Flag.Lookup("output").Value.Get().(string)
+	lang := cmdr.Flag.Lookup("lang").Value.Get().(string)
 
 	cwd, err := os.Getwd()
 	if err != nil {
@@ -69,7 +70,7 @@ func gopyRunCmdBind(cmdr *commander.Command, args []string) error {
 	}
 
 	path := args[0]
-	pkg, err := build.Import(path, cwd, 0)
+	pkg, err := newPackage(path)
 	if err != nil {
 		return fmt.Errorf(
 			"gopy-bind: go/build.Inport failed with path=%q: %v\n",
@@ -90,30 +91,12 @@ func gopyRunCmdBind(cmdr *commander.Command, args []string) error {
 	}
 	//defer os.RemoveAll(work)
 
-	cmd := exec.Command(
-		"gopy", "gen",
-		"-output", work,
-		"-lang=python", pkg.ImportPath,
-	)
-	cmd.Stdin = os.Stdin
-	cmd.Stdout = os.Stdout
-	cmd.Stderr = os.Stderr
-
-	err = cmd.Run()
+	err = genPkg(work, pkg, lang)
 	if err != nil {
 		return err
 	}
 
-	cmd = exec.Command(
-		"gopy", "gen",
-		"-output", work,
-		"-lang=go", pkg.ImportPath,
-	)
-	cmd.Stdin = os.Stdin
-	cmd.Stdout = os.Stdout
-	cmd.Stderr = os.Stderr
-
-	err = cmd.Run()
+	err = genPkg(work, pkg, "go")
 	if err != nil {
 		return err
 	}
@@ -129,9 +112,9 @@ func gopyRunCmdBind(cmdr *commander.Command, args []string) error {
 	}
 	defer os.RemoveAll(wbind)
 
-	cmd = exec.Command(
+	cmd := exec.Command(
 		"go", "build", "-v", "-buildmode=c-shared",
-		"-o", filepath.Join(wbind, pkg.Name)+".so",
+		"-o", filepath.Join(wbind, pkg.Name())+".so",
 		//	pkg.ImportPath,
 		".",
 	)
@@ -146,8 +129,8 @@ func gopyRunCmdBind(cmdr *commander.Command, args []string) error {
 
 	cmd = exec.Command(
 		"/bin/cp",
-		filepath.Join(wbind, pkg.Name)+".so",
-		filepath.Join(odir, pkg.Name)+".so",
+		filepath.Join(wbind, pkg.Name())+".so",
+		filepath.Join(odir, pkg.Name())+".so",
 	)
 	cmd.Stdin = os.Stdin
 	cmd.Stdout = os.Stdout

cmd_gen.go

@@ -6,7 +6,6 @@ package main
 
 import (
 	"fmt"
-	"go/build"
 	"log"
 	"os"
 	"path/filepath"
@@ -73,7 +72,7 @@ func gopyRunCmdGen(cmdr *commander.Command, args []string) error {
 	}
 
 	path := args[0]
-	pkg, err := build.Import(path, cwd, 0)
+	pkg, err := newPackage(path)
 	if err != nil {
 		return fmt.Errorf(
 			"gopy-gen: go/build.Inport failed with path=%q: %v\n",

gen.go

@@ -26,31 +26,22 @@ var (
 	fset = token.NewFileSet()
 )
 
-func genPkg(odir string, pkg *build.Package, lang string) error {
+func genPkg(odir string, p *bind.Package, lang string) error {
 	var err error
 	var o *os.File
 
-	files, err := parseFiles(pkg.Dir, pkg.GoFiles)
-	if err != nil {
-		return err
-	}
-
-	conf := loader.Config{
-		Fset: fset,
-	}
-	conf.TypeChecker.Error = func(e error) {
-		log.Printf("%v\n", e)
-		err = e
-	}
-
-	p, err := newPackage(files, &conf, pkg)
-	if err != nil {
-		log.Printf("%v\n", err)
-		return err
+	switch lang {
+	case "python", "py":
+		lang, err = getPythonVersion()
+		if err != nil {
+			return err
+		}
+	default:
+		// no-op
 	}
 
 	switch lang {
-	case "python", "py":
+	case "python2", "py2":
 		o, err = os.Create(filepath.Join(odir, p.Name()+".c"))
 		if err != nil {
 			return err
@@ -61,6 +52,9 @@ func genPkg(odir string, pkg *build.Package, lang string) error {
 			return err
 		}
 
+	case "python3", "py3":
+		return fmt.Errorf("gopy: python-3 support not yet implemented")
+
 	case "go":
 		o, err = os.Create(filepath.Join(odir, p.Name()+".go"))
 		if err != nil {
@@ -147,7 +141,36 @@ func parseFiles(dir string, fnames []string) ([]*ast.File, error) {
 	return files, err
 }
 
-func newPackage(files []*ast.File, conf *loader.Config, pkg *build.Package) (*bind.Package, error) {
+func newPackage(path string) (*bind.Package, error) {
+	cwd, err := os.Getwd()
+	if err != nil {
+		return nil, err
+	}
+
+	pkg, err := build.Import(path, cwd, 0)
+	files, err := parseFiles(pkg.Dir, pkg.GoFiles)
+	if err != nil {
+		return nil, err
+	}
+
+	conf := loader.Config{
+		Fset: fset,
+	}
+	conf.TypeChecker.Error = func(e error) {
+		log.Printf("%v\n", e)
+		err = e
+	}
+
+	p, err := newPackageFrom(files, &conf, pkg)
+	if err != nil {
+		log.Printf("%v\n", err)
+		return nil, err
+	}
+
+	return p, err
+}
+
+func newPackageFrom(files []*ast.File, conf *loader.Config, pkg *build.Package) (*bind.Package, error) {
 
 	conf.CreateFromFiles(pkg.ImportPath, files...)
 	program, err := conf.Load()

python.go

@@ -0,0 +1,45 @@
+// Copyright 2015 The go-python Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"os/exec"
+)
+
+// getPythonVersion returns the python version available on this machine
+func getPythonVersion() (string, error) {
+	py, err := exec.LookPath("python")
+	if err != nil {
+		return "", fmt.Errorf(
+			"gopy: could not locate 'python' executable (err: %v)",
+			err,
+		)
+	}
+
+	out, err := exec.Command(py, "--version").Output()
+	if err != nil {
+		return "", fmt.Errorf(
+			"gopy: error retrieving python version (err: %v)",
+			err,
+		)
+	}
+
+	vers := ""
+	switch {
+	case bytes.HasPrefix(out, []byte("Python 2")):
+		vers = "py2"
+	case bytes.HasPrefix(out, []byte("Python 3")):
+		vers = "py3"
+	default:
+		return "", fmt.Errorf(
+			"gopy: invalid python version (%s)",
+			string(out),
+		)
+	}
+
+	return vers, nil
+}