added tests for IP address parsing

parse_test.go

@@ -1,6 +1,7 @@
 package arg
 
 import (
+	"net"
 	"os"
 	"strings"
 	"testing"
@@ -541,3 +542,40 @@ func TestSliceUnmarhsaler(t *testing.T) {
 	assert.EqualValues(t, 5, (*args.Foo)[0])
 	assert.Equal(t, "xyz", args.Bar)
 }
+
+func TestIP(t *testing.T) {
+	var args struct {
+		Host net.IP
+	}
+	err := parse("--host 192.168.0.1", &args)
+	require.NoError(t, err)
+	assert.Equal(t, "192.168.0.1", args.Host.String())
+}
+
+func TestPtrToIP(t *testing.T) {
+	var args struct {
+		Host *net.IP
+	}
+	err := parse("--host 192.168.0.1", &args)
+	require.NoError(t, err)
+	assert.Equal(t, "192.168.0.1", args.Host.String())
+}
+
+func TestIPSlice(t *testing.T) {
+	var args struct {
+		Host []net.IP
+	}
+	err := parse("--host 192.168.0.1 127.0.0.1", &args)
+	require.NoError(t, err)
+	require.Len(t, args.Host, 2)
+	assert.Equal(t, "192.168.0.1", args.Host[0].String())
+	assert.Equal(t, "127.0.0.1", args.Host[1].String())
+}
+
+func TestInvalidIPAddress(t *testing.T) {
+	var args struct {
+		Host net.IP
+	}
+	err := parse("--host xxx", &args)
+	assert.Error(t, err)
+}

scalar.go

@@ -93,18 +93,21 @@ func setScalar(v reflect.Value, s string) error {
 			return err
 		}
 		v.Set(reflect.ValueOf(*addr))
+		return nil
 	case net.IP:
 		ip := net.ParseIP(s)
 		if ip == nil {
 			return fmt.Errorf(`invalid IP address: "%s"`, s)
 		}
 		v.Set(reflect.ValueOf(ip))
+		return nil
 	case net.HardwareAddr:
 		ip, err := net.ParseMAC(s)
 		if err != nil {
 			return err
 		}
 		v.Set(reflect.ValueOf(ip))
+		return nil
 	}
 
 	// Switch on kind so that we can handle derived types