commands: Cleaned up argument validation

commands/command.go

@@ -140,40 +140,37 @@ func (c *Command) GetOptions(path []string) (map[string]Option, error) {
 }
 
 func (c *Command) CheckArguments(req Request) error {
-	var argDef Argument
 	args := req.Arguments()
+	argDefs := c.Arguments
 
-	var length int
+	// if we have more arg values provided than argument definitions,
-	if len(args) > len(c.Arguments) {
+	// and the last arg definition is not variadic (or there are no definitions), return an error
-		length = len(args)
+	notVariadic := len(argDefs) == 0 || !argDefs[len(argDefs)-1].Variadic
-	} else {
+	if notVariadic && len(args) > len(argDefs) {
-		length = len(c.Arguments)
+		return fmt.Errorf("Expected %v arguments, got %v", len(argDefs), len(args))
 	}
 
-	for i := 0; i < length; i++ {
+	// iterate over the arg definitions
-		var arg interface{}
+	for i, argDef := range c.Arguments {
-		if len(args) > i {
+
-			arg = args[i]
+		// the value for this argument definition. can be nil if it wasn't provided by the caller
+		var v interface{}
+		if i < len(args) {
+			v = args[i]
 		}
 
-		if i < len(c.Arguments) {
+		err := checkArgValue(v, argDef)
-			argDef = c.Arguments[i]
+		if err != nil {
-		} else if !argDef.Variadic {
+			return err
-			return fmt.Errorf("Expected %v arguments, got %v", len(c.Arguments), len(args))
 		}
 
-		if argDef.Required && arg == nil {
+		// any additional values are for the variadic arg definition
-			return fmt.Errorf("Argument '%s' is required", argDef.Name)
+		if argDef.Variadic && i < len(args)-1 {
+			for _, val := range args[i+1:] {
+				err := checkArgValue(val, argDef)
+				if err != nil {
+					return err
 				}
-		if argDef.Type == ArgFile {
-			_, ok := arg.(io.Reader)
-			if !ok {
-				return fmt.Errorf("Argument '%s' isn't valid", argDef.Name)
-			}
-		} else if argDef.Type == ArgString {
-			_, ok := arg.(string)
-			if !ok {
-				return fmt.Errorf("Argument '%s' must be a string", argDef.Name)
 			}
 		}
 	}
@@ -185,3 +182,29 @@ func (c *Command) CheckArguments(req Request) error {
 func (c *Command) Subcommand(id string) *Command {
 	return c.Subcommands[id]
 }
+
+// checkArgValue returns an error if a given arg value is not valid for the given Argument
+func checkArgValue(v interface{}, def Argument) error {
+	if v == nil {
+		if def.Required {
+			return fmt.Errorf("Argument '%s' is required", def.Name)
+		}
+
+		return nil
+	}
+
+	if def.Type == ArgFile {
+		_, ok := v.(io.Reader)
+		if !ok {
+			return fmt.Errorf("Argument '%s' isn't valid", def.Name)
+		}
+
+	} else if def.Type == ArgString {
+		_, ok := v.(string)
+		if !ok {
+			return fmt.Errorf("Argument '%s' must be a string", def.Name)
+		}
+	}
+
+	return nil
+}