Add ChoiceFlag

[Poweranimal]

A cli flag used for enums.
The flag displays all possible enum variations in the cli's help message and verifies the provided input value.

What type of PR is this?

• feature

What this PR does / why we need it:

This PR adds an enum flag implementation.

Special notes for your reviewer:

I'm open for any suggestion to fulfill the job of supporting an enum flag better.

Example

type LogFormat int32

const (
    LogFormatJSON LogFormat = iota
    LogFormatText
)

type LogMode in32

const (
    LogModeNoop LogMode = iota
    LogModeStdout
)

var logModeMap = map[LogMode]string{
    LogModeNoop: "noop",
    LogModeStdout: "stdout",
}

func (m LogMode) String() string {
    return logModeMap[m]
}

var (
    destFormat LogFormat
    destLevel string
)

var LogFormatFlag = &cli.ChoiceFlag{
    Name:         "log-format",
    Value:          LogFormatJSON,
    Choice:        cli.NewChoice(map[string]interface{}{
        "json": LogFormatJSON,
        "text":  LogFormatText,
    },
    Destination: &destFormat,
    EnvVars:      []string{"LOG_FORMAT"},
    Usage:         "The output formatting of the logger.",
    Required:     false,
}

var LogModeFlag = &cli.ChoiceFlag{
    Name:         "log-mode",
    Value:          LogModeStdout,
    Choice:        cli.NewStringerChoice(LogModeNoop, LogModeStdout),
    EnvVars:      []string{"LOG_MODE"},
    Usage:         "The log mode of the logger.",
}

var LogLevelFlag = &cli.ChoiceFlag{
    Name:         "log-level",
    Value:          "info",
    Choice:        cli.NewStringChoice("debug", "info", "warn", "error"),
    Destination: &destLevel,
    EnvVars:      []string{"LOG_LEVEL"},
    Usage:         "The log level of the logger.",
    Required:     false,
}

Release Notes

Added `cli.ChoiceFlag` for enum support.

TODOS

• Typed destination
• Add tests
• Add README

[dearchap]

Great good.

[dearchap]

I just realised. This is more generic than enums. You could implement an option of choices for strings, ints, etc for this. Maybe rename this to ChoiceFlag ?

[Poweranimal]

I just realised. This is more generic than enums. You could implement an option of choices for strings, ints, etc for this. Maybe rename this to ChoiceFlag ?

Yeah, that sounds better.
I renamed 'enum' to 'choice'

[Poweranimal]

@dearchap Regarding adding a Destination.
This seems a bit more complicated.
As of now, this package uses for destination the flag package of the golang stdlib.
It doesn't play well with the ChoiceHolder.
Let me see, if I figure out how one can support this...

[Poweranimal]

I added destination to the ChoiceFlag and improved its API.

[dearchap]

You should also write some unit tests for this for completion.

[Poweranimal]

I did some changes to the ChoiceFlag;

• Replaced ChoiceHolder with interface{}
• Renamed ChoiceDecoder to Choice
• Added ToString to Choice
• Added helper Choice constructors: NewChoice and NewStringChoice

[marcofranssen]

We might also want to update the README.md with usage example and documenting the availabiltiy of this param type.

[marcofranssen]

What is the state of this PR? Seems only blocked on some missing code coverage for the new feature. @Poweranimal is that something you could finalize?

[Poweranimal]

Hi @marcofranssen
I got quite demotivated to continue due to the lack of engagement by the maintainers.

Thus, I got the impression that this project is EOL and doesn't welcome pr's anymore.

[abdennour]

@Poweranimal , you did great job. I hope better response from maintainers

[meatballhat]

@Poweranimal Hello and sorry for the long delay 😭 Please come back! This whole global pandemic thing and various maintainers' life adventures have seriously impacted responsiveness, but we're trying to get stuff flowing again now.

[meatballhat]

Connected to #602

[jalavosus]

@Poweranimal if you could rebase this onto the current main branch, I'd love to review this and get it merged.

Edit to add: rebase and add some tests to this, both for codecov happiness reasons as well as that having tests is usually a good thing.

Thanks! :D

[Poweranimal]

Hi @jalavosus ,
I’ve quit using this repo for quite l long time now.
Please feel free to to reuse my branch as you like.

[dearchap]

@meatballhat I think this is a good feature but there are many ways to go about it. Either the ChoiceFlag as given here or a Choice interface can be added to each flag(IntFlag, StringFlag etc) in the generated code. I am inkling towards the latter approach. I can work on it if you think its the right direction.

[meatballhat]

@dearchap I would love to see what you have in mind for a Choice interface!

[dearchap]

This approach has been considered but dropped due to favoring a different mechanism using a validation API. That would allow ALL flags to use validation code instead of creating a new Flag