Function buildChild

build.go:249–311

(k *Kong, node *Node, typ NodeType, v reflect.Value, ft reflect.StructField, fv reflect.Value, tag *Tag, name string, seenFlags map[string]bool)

}

func buildChild(k *Kong, node *Node, typ NodeType, v reflect.Value, ft reflect.StructField, fv reflect.Value, tag *Tag, name string, seenFlags map[string]bool) error {
	child, err := buildNode(k, fv, typ, newEmptyTag(), seenFlags)
	if err != nil {
		return err
	}
	child.Name = name
	child.Tag = tag
	child.Parent = node
	child.Help = tag.Help
	child.Hidden = tag.Hidden
	child.Group = buildGroupForKey(k, tag.Group)
	child.Aliases = tag.Aliases

	if provider, ok := fv.Addr().Interface().(HelpProvider); ok {
		child.Detail = provider.Help()
	}

	// A branching argument. This is a bit hairy, as we let buildNode() do the parsing, then check that
	// a positional argument is provided to the child, and move it to the branching argument field.
	if tag.Arg {
		if len(child.Positional) == 0 {
			return failField(v, ft, "positional branch must have at least one child positional argument named %q", name)
		}
		if child.Positional[0].Name != name {
			return failField(v, ft, "first field in positional branch must have the same name as the parent field (%s).", child.Name)
		}

		child.Argument = child.Positional[0]
		child.Positional = child.Positional[1:]
		if child.Help == "" {
			child.Help = child.Argument.Help
		}
	} else {
		if tag.HasDefault {
			if node.DefaultCmd != nil {
				return failField(v, ft, "can't have more than one default command under %s", node.Summary())
			}
			if tag.Default != "withargs" && (len(child.Children) > 0 || len(child.Positional) > 0) {
				return failField(v, ft, "default command %s must not have subcommands or arguments", child.Summary())
			}
			node.DefaultCmd = child
		}
		if tag.Passthrough {
			if len(child.Children) > 0 || len(child.Flags) > 0 {
				return failField(v, ft, "passthrough command %s must not have subcommands or flags", child.Summary())
			}
			if len(child.Positional) != 1 {
				return failField(v, ft, "passthrough command %s must contain exactly one positional argument", child.Summary())
			}
			if !checkPassthroughArg(child.Positional[0].Target) {
				return failField(v, ft, "passthrough command %s must contain exactly one positional argument of []string type", child.Summary())
			}
			child.Passthrough = true
		}
	}
	node.Children = append(node.Children, child)

	if len(child.Positional) > 0 && len(child.Children) > 0 {