Proposal: move code out of tool.go

[paralin]

Right now there is a lot of code in tool.go, defined under in-line functions.

Ideally this code would be broken out into packages accessible when using Gopherjs as a library:

	sess, err := gbuild.NewSession(&opts)
	if err != nil {
		return err
	}

	xctx := gbuild.NewBuildContext(sess.InstallSuffix(), opts.BuildTags)
	pkgs, err := xctx.Match(args)

^^ These steps :)

[nevkontakte]

Yes, a lot of what's currently in tool.go should really be in the build package. In theory, you can already do a lot with the build package, though beware that breaking changes to that package API can and will happen :)

[paralin]

Indeed, this is my build script:

	// list of packages to build
	args := []string{"github.com/my/project"}

	// build the js
	runtimeOut := path.Join(runtimeDir, "runtime-gopherjs.js")

	// hack: disable version check
	os.Setenv("GOPHERJS_SKIP_VERSION_CHECK", "true")

	opts := BuildOptions
	opts.GOROOT = runtime.GOROOT()
	opts.GOPATH = ""

	sess, err := gbuild.NewSession(&opts)
	if err != nil {
		return err
	}

	xctx := gbuild.NewBuildContext(sess.InstallSuffix(), opts.BuildTags)
	pkgs, err := xctx.Match(args)
	if err != nil {
		return errors.Wrapf(err, "failed to expand patterns: %v", args)
	}
	if len(pkgs) != 1 {
		return errors.Errorf("expected %d packages but got %d", 1, len(pkgs))
	}

	pkgPath := pkgs[0]
	pkg, err := xctx.Import(pkgPath, repoRoot, 0)
	if err != nil {
		return err
	}
	if !pkg.IsCommand() {
		return errors.Errorf("expected package with main function: %s", pkg.ImportPath)
	}

	ar, err := sess.BuildPackage(pkg)
	if err != nil {
		return err
	}

	err = sess.WriteCommandPackage(ar, runtimeOut)
	if err != nil {
		return err
	}

	return nil
}