Impossible to provide completions for combined syntax of string-to-string flags

[Airblader]

Let's say we have a --set=key=value flag that can be repeated, e.g. --set=k1=v1 --set=k2=v2. The string-to-string flag also supports a shorter syntax of --set=k1=v1,k2=v2. However, it appears to be impossible to provide completions for this combined syntax.

This is related to #1981, but there it was about string slice flags (where this does work); I cannot get the same to work for string-to-string flags.

If I ignore the prefix (everything up until the comma), completions just get filtered out. But if I try to provide the full prefix:

possibleCompletions := []string{"k2=v2", "k2=v3"}

func(cmd *cobra.Command, _ []string, toComplete string) ([]string, cobra.ShellCompDirective) {
	commaLastIndex := strings.LastIndex(toComplete, ",")

	var prefix string
	if commaLastIndex > -1 {
		prefix = toComplete[:commaLastIndex+1]
		toComplete = toComplete[commaLastIndex+1:]
	}

	out := make([]string, 0)
	for _, possibleCompletion := range possibleCompletions {
		out = append(out, prefix+possibleCompletion)
	}

	return out, cobra.ShellCompDirectiveNoFileComp
}

then completing cli --set=k1=v1,<TAB> results in cli --set=k1=k1=v1,k2=v.

[marckhouzam]

This is a pretty complex case that was probably overlooked. Can you try without the first equal sign, which is another form that Cobra supports to specify flag values.

Can you also specify which shell you are using?

[Airblader]

Can you try without the first equal sign, which is another form that Cobra supports to specify flag values.

Yeah, that appears to work.

Can you also specify which shell you are using?

I'm on zsh (MacOS).

[eyu24]

To avoid this duplication and make completions work more intuitively, you can use a trick: return only the suffixes as completions, and let Cobra handle the prefix automatically.

[eyu24]

To avoid this duplication and make completions work more intuitively, you can use a trick: return only the suffixes as completions, and let Cobra handle the prefix automatically.

Here's how:
func(cmd *cobra.Command, _ []string, toComplete string) ([]string, cobra.ShellCompDirective) {
commaLastIndex := strings.LastIndex(toComplete, ",")

if commaLastIndex > -1 {
    toComplete = toComplete[commaLastIndex+1:]
}

possibleCompletions := []string{"k2=v2", "k2=v3"}
out := make([]string, 0)
for _, c := range possibleCompletions {
    if strings.HasPrefix(c, toComplete) {
        out = append(out, c)
    }
}

return out, cobra.ShellCompDirectiveNoFileComp

}

[Airblader]

@llyas36 That doesn't work and just doesn't complete anything.