Call Validate() functions on nodes if present.

context.go

@@ -44,6 +44,27 @@ func (p *Path) Node() *Node {
 	return nil
 }
 
+// Visitable returns the Visitable for this path element.
+func (p *Path) Visitable() Visitable {
+	switch {
+	case p.App != nil:
+		return p.App
+
+	case p.Argument != nil:
+		return p.Argument
+
+	case p.Command != nil:
+		return p.Command
+
+	case p.Flag != nil:
+		return p.Flag
+
+	case p.Positional != nil:
+		return p.Positional
+	}
+	return nil
+}
+
 // Context contains the current parse context.
 type Context struct {
 	*Kong
@@ -136,10 +157,19 @@ func (c *Context) Empty() bool {
 // Validate the current context.
 func (c *Context) Validate() error { // nolint: gocyclo
 	err := Visit(c.Model, func(node Visitable, next Next) error {
-		if value, ok := node.(*Value); ok {
-			_, ok := os.LookupEnv(value.Tag.Env)
-			if value.Enum != "" && (!value.Required || value.Default != "" || (value.Tag.Env != "" && ok)) {
-				if err := checkEnum(value, value.Target); err != nil {
+		switch node := node.(type) {
+		case *Value:
+			_, ok := os.LookupEnv(node.Tag.Env)
+			if node.Enum != "" && (!node.Required || node.Default != "" || (node.Tag.Env != "" && ok)) {
+				if err := checkEnum(node, node.Target); err != nil {
+					return err
+				}
+			}
+
+		case *Flag:
+			_, ok := os.LookupEnv(node.Tag.Env)
+			if node.Enum != "" && (!node.Required || node.Default != "" || (node.Tag.Env != "" && ok)) {
+				if err := checkEnum(node.Value, node.Target); err != nil {
 					return err
 				}
 			}
@@ -149,6 +179,35 @@ func (c *Context) Validate() error { // nolint: gocyclo
 	if err != nil {
 		return err
 	}
+	for _, el := range c.Path {
+		var (
+			value reflect.Value
+			desc  string
+		)
+		switch node := el.Visitable().(type) {
+		case *Value:
+			value = node.Target
+			desc = node.ShortSummary()
+
+		case *Flag:
+			value = node.Target
+			desc = node.ShortSummary()
+
+		case *Application:
+			value = node.Target
+			desc = node.Name
+
+		case *Node:
+			value = node.Target
+			desc = node.Path()
+		}
+		if validate := isValidatable(value); validate != nil {
+			err := validate.Validate()
+			if err != nil {
+				return errors.Wrap(err, desc)
+			}
+		}
+	}
 	for _, resolver := range c.combineResolvers() {
 		if err := resolver.Validate(c.Model); err != nil {
 			return err
@@ -787,3 +846,18 @@ func findPotentialCandidates(needle string, haystack []string, format string, ar
 	}
 	return fmt.Errorf("%s", prefix)
 }
+
+type validatable interface{ Validate() error }
+
+func isValidatable(v reflect.Value) validatable {
+	if !v.IsValid() || (v.Kind() == reflect.Ptr || v.Kind() == reflect.Slice || v.Kind() == reflect.Map) && v.IsNil() {
+		return nil
+	}
+	if validate, ok := v.Interface().(validatable); ok {
+		return validate
+	}
+	if v.CanAddr() {
+		return isValidatable(v.Addr())
+	}
+	return nil
+}