func doMain()

in cmd/starlark/starlark.go [54:148]
83 lines of code
14 McCabe index (conditional complexity)

func doMain() int {
	log.SetPrefix("starlark: ")
	log.SetFlags(0)
	flag.Parse()

	if *cpuprofile != "" {
		f, err := os.Create(*cpuprofile)
		check(err)
		err = pprof.StartCPUProfile(f)
		check(err)
		defer func() {
			pprof.StopCPUProfile()
			err := f.Close()
			check(err)
		}()
	}
	if *memprofile != "" {
		f, err := os.Create(*memprofile)
		check(err)
		defer func() {
			runtime.GC()
			err := pprof.Lookup("heap").WriteTo(f, 0)
			check(err)
			err = f.Close()
			check(err)
		}()
	}

	if *profile != "" {
		f, err := os.Create(*profile)
		check(err)
		err = starlark.StartProfile(f)
		check(err)
		defer func() {
			err := starlark.StopProfile()
			check(err)
		}()
	}

	thread := &starlark.Thread{Load: repl.MakeLoad()}
	globals := make(starlark.StringDict)

	// Ideally this statement would update the predeclared environment.
	// TODO(adonovan): plumb predeclared env through to the REPL.
	starlark.Universe["json"] = json.Module
	starlark.Universe["time"] = time.Module
	starlark.Universe["math"] = math.Module

	switch {
	case flag.NArg() == 1 || *execprog != "":
		var (
			filename string
			src      interface{}
			err      error
		)
		if *execprog != "" {
			// Execute provided program.
			filename = "cmdline"
			src = *execprog
		} else {
			// Execute specified file.
			filename = flag.Arg(0)
		}
		thread.Name = "exec " + filename
		globals, err = starlark.ExecFile(thread, filename, src, nil)
		if err != nil {
			repl.PrintError(err)
			return 1
		}
	case flag.NArg() == 0:
		stdinIsTerminal := term.IsTerminal(int(os.Stdin.Fd()))
		if stdinIsTerminal {
			fmt.Println("Welcome to Starlark (go.starlark.net)")
		}
		thread.Name = "REPL"
		repl.REPL(thread, globals)
		if stdinIsTerminal {
			fmt.Println()
		}
	default:
		log.Print("want at most one Starlark file name")
		return 1
	}

	// Print the global environment.
	if *showenv {
		for _, name := range globals.Keys() {
			if !strings.HasPrefix(name, "_") {
				fmt.Fprintf(os.Stderr, "%s = %s\n", name, globals[name])
			}
		}
	}

	return 0
}