add MarkIfFlagPresentThenOthersRequired

[faizan-siddiqui]

This PR introduces a new flag group function, MarkIfFlagPresentThenOthersRequired, which enforces a "one-way required together" relationship among flags. This means that if a primary flag is set, then other dependent flags must also be set. This allows users to make certain flags conditionally required based on the presence of another flag, while maintaining flexibility when the primary flag is not provided.

Example

Consider a command called get-range that uses the flags --start and --end to specify a date range. By default, the command can run without either flag, using default start and end values (e.g., start=someDefaultStart and end=Now). However, you may want to enforce that if the user specifies an --end, they must also specify a --start.

cmd := &cobra.Command{
    Use: "get-range",
}

cmd.Flags().String("start", "", "Start date")
cmd.Flags().String("end", "", "End date")

// If --end is set, --start is required
cmd.MarkIfFlagPresentThenRequired("end", "start")

• If the command is called with only --end=value, it will trigger an error because --start is missing.
• If called without any flags or only with --start, it will run using the default values or the provided start date.

This change makes it easier to enforce dependencies between flags while allowing flexible defaults when the primary flag is not specified.

[CLAassistant]

All committers have signed the CLA.

[faizan-siddiqui]

@marckhouzam Would love to get this in thanks! Let me know if you have any questions :)

[faizan-siddiqui]

@dpetersen @markbates @EdwardBetts Would love to get this in thanks! Let me know if you have any questions :)

[danpalmer]

@marckhouzam is there anything we can do to get this moving? Alternatively we're happy to have discussions about it being out of scope, it just felt fairly obviously useful to us.

[marckhouzam]

I like the idea. I’ll put it on my queue to review. Thank you.

[ccoVeille]

Suggested change

	if len(unset) > 0 {
	return fmt.Errorf(
	"if the first flag in the group [%v] is set, all other flags must be set; the following flags are not set: %v",
	flagList, unset,
	)
	}
	if len(unset) > 0 {
	return fmt.Errorf(
	"%v is set, all other flags [%v] must be set; the following flags are not set: %v",
	flagList[0], flagList[1:], unset,
	)
	}

Maybe something like this would be more readable and understood

Or this

Suggested change

	if len(unset) > 0 {
	return fmt.Errorf(
	"if the first flag in the group [%v] is set, all other flags must be set; the following flags are not set: %v",
	flagList, unset,
	)
	}
	if len(unset) > 0 {
	return fmt.Errorf(
	"%v is set, the following flags must be provided: %v",
	flagList[0], unset,
	)
	}

[ccoVeille]

Can you add a test about using

Suggested change

	flagGroupsIfPresentThenRequired: []string{"a b"},
	flagGroupsIfPresentThenRequired: []string{"a b", "b a"},

This one is similar to the required group that also exists.

Then, it's up to you to decide if it should be discouraged or not

Please also consider adding a test about

Suggested change

	flagGroupsIfPresentThenRequired: []string{"a b"},
	flagGroupsIfPresentThenRequired: []string{"a b", "a c"},

Sane here, you should decide if you want to discourage it or not

Same about a test about

Suggested change

	flagGroupsIfPresentThenRequired: []string{"a b"},
	flagGroupsIfPresentThenRequired: []string{"a b c", "a c b"},

Suggested change

	flagGroupsIfPresentThenRequired: []string{"a b"},
	flagGroupsIfPresentThenRequired: []string{"a b c", "b c"},

I'm asking for all these tests because I'm unsure how it would be expected to work

[ccoVeille]

Suggested change

	// - when the first flag in an if-present-then-required group is present, the second flag will be marked as required
	// - when the first flag in an if-present-then-required group is present, the other flags will be marked as required