removed duplicated code and simplified a little in validate

commands_test.go

@@ -180,7 +180,7 @@ func TestCommandCalled(t *testing.T) {
 	}
 }
 
-func TestOption(t *testing.T) {
+func TestOption(t *testing.T) { //nolint:funlen // it's okay to be long
 	called := false
 
 	type argv struct {
@@ -208,7 +208,11 @@ func TestOption(t *testing.T) {
 
 	builder := new(strings.Builder)
 	cmd.SetOutput(builder)
-	cmd.Run([]string{"-x", "foo"}) // wrong type for int
+
+	err = cmd.RunError([]string{"-x", "foo"}) // wrong type for int
+	if err == nil {
+		t.Error("expected an error")
+	}
 
 	if called {
 		t.Error("The command shouldn't be called")

validate.go

@@ -4,29 +4,29 @@ import (
 	"github.com/mailund/cli/interfaces"
 )
 
+func validate(flag bool, v interface{}) error {
+	if val, ok := v.(interfaces.Validator); ok {
+		return val.Validate(flag)
+	}
+
+	return nil
+}
+
 func validateFlagsAndParams(cmd *Command) error {
 	for i := 0; i < cmd.flags.NFlags(); i++ {
-		if v, ok := cmd.flags.Flag(i).Value.(interfaces.Validator); ok {
-			if err := v.Validate(true); err != nil {
-				return err
-			}
+		if err := validate(true, cmd.flags.Flag(i).Value); err != nil {
+			return err
 		}
 	}
 
 	for i := 0; i < cmd.params.NParams(); i++ {
-		if v, ok := cmd.params.Param(i).Value.(interfaces.Validator); ok {
-			if err := v.Validate(false); err != nil {
-				return err
-			}
+		if err := validate(false, cmd.params.Param(i).Value); err != nil {
+			return err
 		}
 	}
 
 	if vv := cmd.params.Variadic(); vv != nil {
-		if v, ok := vv.Value.(interfaces.Validator); ok {
-			if err := v.Validate(false); err != nil {
-				return err
-			}
-		}
+		return validate(false, vv.Value)
 	}
 
 	return nil