For consistency, I think it would be useful to have MinimumValidNArgs(int), MaximumValidNArgs(int) and RangeValidArgs(min, max) added to the list of supported Args formats. The complete list would then be:

• NoArgs
• ArbitraryArgs
• OnlyValidArgs
• MinimumNArgs(int)
• +MinimumValidNArgs(int)
• MaximumNArgs(int)
• +MaximumValidNArgs(int)
• ExactArgs(int)
• ExactValidArgs(int)
• RangeArgs(min, max)
• +RangeValidArgs(min, max)

This is because AFAIK it is not possible ATM to combine e.g. MinimumNArgs(1) with OnlyValidArgs.

An alternative solution is to provide a built-in function such as matchAll by @Antolius in #745. For example:

func MatchValid(p cobra.PositionalArgs) cobra.PositionalArgs {
	return func(cmd *cobra.Command, args []string) error {
		if err := cobra.OnlyValidArgs(cmd, args); err != nil {
			return err
		}
		if err := p(cmd, args); err != nil {
			return err
		}
		return nil
	}
}

which would allow the following expressions:

• Args: cobra.MatchValid(cobra.MinimumNArgs(1)), ValidArgs: []string{...}
• Args: cobra.MatchValid(cobra.MaximumNArgs(5)), ValidArgs: []string{...}
• Args: cobra.MatchValid(cobra.RangeArgs(1, 5)), ValidArgs: []string{...}
• Args: cobra.MatchValid(cobra.ArbitraryArgs), ValidArgs: []string{...}
• Args: cobra.MatchValid(cobra.ExactArgs(1)), ValidArgs: []string{...}

Certainly, MatchValid can be used implicitly when ValidArgs is defined, so the user is not required to type it. Therefore, OnlyValidArgs and ExactValidArgs can be deprecated from the public API. The list of formats would be:

• NoArgs
• ArbitraryArgs
• MinimumNArgs(int)
• MaximumNArgs(int)
• ExactArgs(int)
• RangeArgs(min, max)