Pass functions to ConfigureOptions to print version, help, tls help

This will allow NATS Streaming to provide its own version of what
should be printed when various flags are set.

Related to #578

main.go

@@ -68,7 +68,10 @@ func main() {
 	fs.Usage = usage
 
 	// Configure the options from the flags/config file
-	opts, err := server.ConfigureOptions(fs, os.Args[1:])
+	opts, err := server.ConfigureOptions(fs, os.Args[1:],
+		server.PrintServerAndExit,
+		fs.Usage,
+		server.PrintTLSHelpAndDie)
 	if err != nil {
 		server.PrintAndDie(err.Error() + "\n" + usageStr)
 	}

server/opts.go

@@ -921,7 +921,7 @@ func processOptions(opts *Options) {
 // specific flags. On success, an options structure is returned configured
 // based on the selected flags and/or configuration file.
 // The command line options take precedence to the ones in the configuration file.
-func ConfigureOptions(fs *flag.FlagSet, args []string) (*Options, error) {
+func ConfigureOptions(fs *flag.FlagSet, args []string, printVersion, printHelp, printTLSHelp func()) (*Options, error) {
 	opts := &Options{}
 	var (
 		showVersion bool
@@ -932,6 +932,8 @@ func ConfigureOptions(fs *flag.FlagSet, args []string) (*Options, error) {
 		err         error
 	)
 
+	fs.BoolVar(&showHelp, "h", false, "Show this message.")
+	fs.BoolVar(&showHelp, "help", false, "Show this message.")
 	fs.IntVar(&opts.Port, "port", 0, "Port to listen on.")
 	fs.IntVar(&opts.Port, "p", 0, "Port to listen on.")
 	fs.StringVar(&opts.Host, "addr", "", "Network host to listen on.")
@@ -990,13 +992,19 @@ func ConfigureOptions(fs *flag.FlagSet, args []string) (*Options, error) {
 		return nil, err
 	}
 
-	// Show version and exit
 	if showVersion {
-		PrintServerAndExit()
+		printVersion()
+		return nil, nil
+	}
+
+	if showHelp {
+		printHelp()
+		return nil, nil
 	}
 
 	if showTLSHelp {
-		PrintTLSHelpAndDie()
+		printTLSHelp()
+		return nil, nil
 	}
 
 	// Process args looking for non-flag options,
@@ -1005,9 +1013,10 @@ func ConfigureOptions(fs *flag.FlagSet, args []string) (*Options, error) {
 	if err != nil {
 		return nil, err
 	} else if showVersion {
-		PrintServerAndExit()
+		printVersion()
+		return nil, nil
 	} else if showHelp {
-		fs.Usage()
+		printHelp()
 		return nil, nil
 	}
 

server/opts_test.go

@@ -826,25 +826,43 @@ func TestConfigureOptions(t *testing.T) {
 	// We need to set it back to nil otherwise it will impact reload tests.
 	defer func() { FlagSnapshot = nil }()
 
-	// Ensure that Usage is called when param "help" is set
-	fs := flag.NewFlagSet("test", flag.ContinueOnError)
 	ch := make(chan bool, 1)
-	fs.Usage = func() {
+	checkPrintInvoked := func() {
 		ch <- true
 	}
-	if _, err := ConfigureOptions(fs, []string{"help"}); err != nil {
-		t.Fatalf("Error on configure: %v", err)
-	}
-	select {
-	case <-ch:
-	case <-time.After(time.Second):
-		t.Fatal("Should have invoked flag set's Usage")
+	usage := func() { panic("should not get there") }
+	var fs *flag.FlagSet
+	type testPrint struct {
+		args                   []string
+		version, help, tlsHelp func()
+	}
+	testFuncs := []testPrint{
+		testPrint{[]string{"-v"}, checkPrintInvoked, usage, PrintTLSHelpAndDie},
+		testPrint{[]string{"version"}, checkPrintInvoked, usage, PrintTLSHelpAndDie},
+		testPrint{[]string{"-h"}, PrintServerAndExit, checkPrintInvoked, PrintTLSHelpAndDie},
+		testPrint{[]string{"help"}, PrintServerAndExit, checkPrintInvoked, PrintTLSHelpAndDie},
+		testPrint{[]string{"-help_tls"}, PrintServerAndExit, usage, checkPrintInvoked},
+	}
+	for _, tf := range testFuncs {
+		fs = flag.NewFlagSet("test", flag.ContinueOnError)
+		opts, err := ConfigureOptions(fs, tf.args, tf.version, tf.help, tf.tlsHelp)
+		if err != nil {
+			t.Fatalf("Error on configure: %v", err)
+		}
+		if opts != nil {
+			t.Fatalf("Expected options to be nil, got %v", opts)
+		}
+		select {
+		case <-ch:
+		case <-time.After(time.Second):
+			t.Fatalf("Should have invoked print function for args=%v", tf.args)
+		}
 	}
 
 	// Helper function that expect parsing with given args to not produce an error.
 	mustNotFail := func(args []string) *Options {
 		fs := flag.NewFlagSet("test", flag.ContinueOnError)
-		opts, err := ConfigureOptions(fs, args)
+		opts, err := ConfigureOptions(fs, args, PrintServerAndExit, fs.Usage, PrintTLSHelpAndDie)
 		if err != nil {
 			stackFatalf(t, "Error on configure: %v", err)
 		}
@@ -858,7 +876,7 @@ func TestConfigureOptions(t *testing.T) {
 		// (flagSet would print error message about unknown flags, etc..)
 		silenceOuput := &bytes.Buffer{}
 		fs.SetOutput(silenceOuput)
-		opts, err := ConfigureOptions(fs, args)
+		opts, err := ConfigureOptions(fs, args, PrintServerAndExit, fs.Usage, PrintTLSHelpAndDie)
 		if opts != nil || err == nil {
 			stackFatalf(t, "Expected no option and an error, got opts=%v and err=%v", opts, err)
 		}