Required flags and optional filename positional arguments by extension do not play together

[scop]

If one sets for a command

	Args: cobra.MaximumNArgs(1),
	ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
		return []string{"foo", "bar", "baz"}, cobra.ShellCompDirectiveFilterFileExt
	},

...and

	var foo string
	serveCmd.Flags().StringVarP(&foo, "hello", "H", "", "Hello the world")
	_ = serveCmd.MarkFlagRequired("hello")

...the resulting completion does not work properly. The required flag(s) get passed "eagerly" to the bash completion filedir function which does not understand the flag, and fails.

With current bash-completion main branch

$ ./my-cli serve <TAB>
[...]
+ __my-cli_debug $'The completions are: --hello\tHello the world\n-H\tHello the world\nfoo\nbar\nbaz\n'
[...]
+ _filedir '--hello|Hello|the|world|-H|Hello|the|world|foo|bar|baz|'
[...]
bash_completion: _comp_compgen_filedir: usage error

A complete example file in a cobra-cli generated project

Details

/*
Copyright © 2026 NAME HERE <EMAIL ADDRESS>

*/
package cmd

import (
	"fmt"

	"github.com/spf13/cobra"
)

// serveCmd represents the serve command
var serveCmd = &cobra.Command{
	Use:   "serve",
	Short: "A brief description of your command",
	Long: `A longer description that spans multiple lines and likely contains examples
and usage of using your command. For example:

Cobra is a CLI library for Go that empowers applications.
This application is a tool to generate the needed files
to quickly create a Cobra application.`,
	Run: func(cmd *cobra.Command, args []string) {
		fmt.Println("serve called")
	},
	Args: cobra.MaximumNArgs(1),
	ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
		return []string{"foo", "bar", "baz"}, cobra.ShellCompDirectiveFilterFileExt
	},
}

func init() {
	var foo string
	serveCmd.Flags().StringVarP(&foo, "hello", "H", "", "Hello the world")
	_ = serveCmd.MarkFlagRequired("hello")

	rootCmd.AddCommand(serveCmd)

	// Here you will define your flags and configuration settings.

	// Cobra supports Persistent Flags which will work for this command
	// and all subcommands, e.g.:
	// serveCmd.PersistentFlags().String("foo", "", "A help for foo")

	// Cobra supports local flags which will only run when this command
	// is called directly, e.g.:
	// serveCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
}

The description here is a specific one, I have not tried out or thought if this might happen with some other configuration combinations. This is with cobra v1.10.2.