add colors to CLI commands

[JulesDT]

Hello

This PR adds an easy way to add colors to commands when they show up in the terminal.

I personally would use this because amongst my commands, some are more important and having a color code would be helpful and seemed easier / less confusing than generating "categories" or groups in the template.

[CLAassistant]

All committers have signed the CLA.

[JulesDT]

I think this answers https://github.com/spf13/cobra/issues/59 but somehow the issue was closed, I'm not sure why

[jpmcb]

Thanks for this! Very cool feature!!

Can you provide a short snipped of how a user might use this?

Thanks much for adding tests. I'll give this a test and we should be able to get it in 2.0

[JulesDT]

Hello,

I currently have 2 use cases for this.

The first one would be to put an emphasis on a few commands in my CLI. I have a lot of available CMDs, and 3 of them are groups that regroups the rest of the commands (One group for collection of data, one group analysis of the data and the last group for modification of the data). So I thought it'd be nice to put some color to make them easier to see in the list of commands.

The second use case was to put a color code on some commands. For example, put in red the commands that might modify data or directly affect production, whereas we can put in green commands that would only read data. Making sure that one can easily see that what they're choosing is potentially a dangerous action.

[jpmcb]

Very cool! Can you provide a snippet of code using this new API? That will help me test.

[JulesDT]

If you do a simple cobra init and add this snippet as a file under cmd/ this should show you two commands. delete should be in red and read in green. (Tested on MacOS Catalina 10.15.7)

package cmd

import (
	"fmt"

	"github.com/spf13/cobra"
)

func init() {
	rootCmd.AddCommand(deleteCmd)
	rootCmd.AddCommand(readCmd)
}

var deleteCmd = &cobra.Command{
	Use:   "delete",
	Short: "Delete hosts in production",
	Long:  `Delete hosts in production`,
	Color: cobra.ColorRed,
	Run: func(cmd *cobra.Command, args []string) {
		fmt.Println("Write CMD")
	},
}

var readCmd = &cobra.Command{
	Use:   "read",
	Short: "read hosts in production",
	Long:  `read hosts in production`,
	Color: cobra.ColorGreen,
	Run: func(cmd *cobra.Command, args []string) {
		fmt.Println("read CMD")
	},
}

[marckhouzam]

After your exchange, I started getting curious about this change.

@jpmcb I hope you don't mind, but I tried it out with Helm which is a larger test.

@JulesDT This is really cool! I noticed a couple of things:

• the name padding isn't working with colours, for example, if I colour the completion command:

$ helm help
[..]
Available Commands:
  2to3            migrate and cleanup Helm v2 configuration and releases in-place to Helm v3
  completion generate autocompletions script for the specified shell
  completion2and3 generate autocompletions script that will work for both helm2 and helm3 together
  conftest        Test Helm Charts
  create          create a new chart with the given name

Notice that the indentation is wrong for completion which is coloured.

Also, the light colours don't seem to work in my case. Maybe it is my terminal? Which brings the question: how portable is this?

Could this be applied to flags?

[JulesDT]

Thanks for testing this! I indeed made a mistake when putting the colors, the sequence starting at ColorDarkGray is shifted by a few digits. I addressed it in my new commit.

Regarding helm I think the issue is that the padding was badly applied indeed. The unseen characters \033[31m and \033[0m for example were counted as respectively 5 and 4 characters even though they would not show up. So I augmented the padding by the length difference between the ColoredName and the Name. This seems to work for helm now. I added a test case to verify that when using colors, there's an additional padding to take this side effect into account.

Let me know if you see anything else that is wrong!

[marckhouzam]

@JulesDT It looks great now. Thanks.

But I cannot figure out what happens if the terminal does not support colours? Will the help/usage text be broken?

This is important because if a program using Cobra wants to add colours, can it do it blindly or does it have to support some option to allow users to disable colours, in case their terminal does not support them? In fact, how would a program allow its user to optionally turn off the colours? Should Cobra provide an easy way to disable colours?

[JulesDT]

That's a good call. I just wasn't able to disable colors in any of the shells I've used. I've tried iterm2, the default terminal, bash, sh in macOS, as well as shells on a linux machine, all were supporting colors, even when setting TERM to xterm-mono or xterm-old.

If you have a way for me to easily disable colors and see how it behaves I'd be happy to push a fix if needed. Detecting if colors are disabled would probably be the best solution, if this can't be done, I guess a config variable that disables colors could work?

I'm tempted to say that people building their own CLI tools will know where it'll run and can enable or disable colors depending on their need, the question arises for global CLI tools (such as helm) where I don't have strong opinion about who should allow to easily disable colors, either the project or Cobra.

[marckhouzam]

That's a good call. I just wasn't able to disable colors in any of the shells I've used. I've tried iterm2, the default terminal, bash, sh in macOS, as well as shells on a linux machine, all were supporting colors, even when setting TERM to xterm-mono or xterm-old.

I tried as well without success.

... the question arises for global CLI tools (such as helm) where I don't have strong opinion about who should allow to easily disable colors, either the project or Cobra.

With the current proposed implementation, how do you see a program such as helm telling Cobra to disable colours? I think it would be nice to provide some easy way to do it.

[JulesDT]

Well, if helm doesn't want to provide Colors because they're afraid of incompatibilities, it's easy for them to simply not use that feature from Cobra. Then with the current implementation is basically follows the same behavior as before.

Do you have an alternative idea in mind? I'm happy to implement a config or a parameter or anything that would allow to disable coloring but I'm not sure how such a feature if it existed should be used.

[marckhouzam]

Sorry @JulesDT I was pretty vague in my last comment.

What I'm imagining is that a program would make use of colors but allow a user to disable them (or vice versa where users would be given the option to enable colors). This could be through a global flag, or some configuration option (that's a detail for the program to choose).

So the question becomes, how would the program easily tell Cobra to turn colors on or off in the same compiled binary?

Thinking about it now, I guess the program could have its own function:

func getColor(color TerminalColor) TerminalColor {
   if globalOptionNoColor {
      return null
   }
    return color
}

But I was wondering if it would be easier for Cobra to provide an option so that ColoredName() could do this disabling.

[JulesDT]

I see. Yeah I wouldn't disagree with giving the user this possibility. In term of design or user experience, I'm not sure what would be the preferred way for Cobra, or what is usually used for such options here.

What I guess a program could do indeed is set a global flag such that if this flag is set ColoredNamed would return the normal name or not. What I suggest for this is the following, but I don't love this design so I'm happy to be told a different way you'd prefer. On the command itself, add a DisableColors bool parameter. And then for the ColoredName method, we can do:

func (c *Command) isColoringDisabled() bool {
	if c.DisableColors {
		return c.DisableColors
	}
	if c.parent != nil {
		return c.parent.isColoringDisabled()
	}
	return false
}

func (c *Command) ColoredName() string {

	if c.Color != 0 && !c.isColoringDisabled() {
		return fmt.Sprintf("\033[%dm%s\033[0m", c.Color, c.Name())
	}
	return c.Name()
}

Then what one could do is add a persistent flag on root to disable colors:

rootCmd.PersistentFlags().BoolVarP(&rootCmd.DisableColors, "disable-colors", "d", false, "disable colors in the terminal")

What do you think @marckhouzam ?

[JulesDT]

@marckhouzam or @jpmcb , any thoughts on this?

[catthehacker]

I suggest following the https://no-color.org/ standard.

[marckhouzam]

I suggest following the https://no-color.org/ standard.

I think respecting a $NO_COLOR environment variable is a good idea. Is that sufficient though? Using NO_COLOR will disable colours for many programs. Does Cobra, as a library to other programs, need to provide a way to disable colours only for the program itself?

[marckhouzam]

@JulesDT Sorry for the delay.

I like your idea of having a DisableColors bool parameter. I don't think we want to allow to disable colours on a per-command basis, so such a boolean parameter could be applicable to the root command only. So then you would do something simple like:

func (c *Command) ColoredName() string {
	if c.Color != 0 && !c.Root().DisableColors {
		return fmt.Sprintf("\033[%dm%s\033[0m", c.Color, c.Name())
	}
	return c.Name()
}

Then, a program could disable colours using a global flag using something like:

	rootCmd.PersistentFlags().BoolVar(&rootCmd.DisableColors, "no-colors", false, "disable colors")

These are just ideas but please be aware I have no final say on this.

[catthehacker]

I suggest following the no-color.org standard.

I think respecting a $NO_COLOR environment variable is a good idea. Is that sufficient though? Using NO_COLOR will disable colours for many programs. Does Cobra, as a library to other programs, need to provide a way to disable colours only for the program itself?

That is the idea behind NO_COLOR environment variable. It's supposed to disable ALL colours for every program. I think that if Cobra is to support colours it should respect NO_COLOR for itself and for any program that is using Cobra. If someone would like to not have colours in Cobra only, they could use the already proposed option of --no-colors. Just my 2c, I would prefer it named --no-color

[marckhouzam]

I think that if Cobra is to support colours it should respect NO_COLOR for itself and for any program that is using Cobra. If someone would like to not have colours in Cobra only, they could use the already proposed option of --no-colors. Just my 2c, I would prefer it named --no-color

Sounds good to me.

[umarcor]

Some thoughts:

• Using viper, the option can be set through a config file, envvars or a flag. Supporting one or several of those options should be up to users of cobra as a library. Hence, I think the discussion above about how to make this a single "global" option (or an option of the root) is enough with regard to the codebase. Then, a usage example can be provided for showcasing how to use it along with viper. Optionally, the template of the cobra cli might be enhanced.

• Many tools try to automatically disable/enable the colour depending on the terminal being a TTY or not. On top of that, options are provided for forcing colouring and/or not colouring. That is, supporting USE_COLOR or FORCE_COLOR as a complement to NO_COLOR. Some tools provide other custom variables/options:

  • https://github.com/tartley/colorama/pull/230
  • https://github.com/tartley/colorama/issues/224
  • https://github.com/pytest-dev/pytest/issues/7443

• There is an issue with GitHub Actions compared to other CI services. Typically, "detection" in CI works and logs are coloured, but that's not the case in Actions: https://github.com/actions/runner/issues/241. Hence, instead of trying to detect whether to enable colours, I think that users should set a default and allow envvars (viper).

  • A workaround in Actions is to run scripts inside a container, which does provide a TTY.

[JulesDT]

@umarcor correct me if I'm wrong, but I think the problem around using viper is that when the help menu is being shown to the user (where the colors are used basically), the config file hasn't been parsed yet. The parsing happens with cobra.OnInitialize(initConfig) which only happens when the command is about to run basically.

Would the --no-color parameter and the NO_COLOR env variable be enough?

[jpmcb]

I would also like to see a test case around the --no-color and NO_COLOR options if possible.

Checking in on this one, where are we at with this PR? Thanks much for the work on this one :D

[JulesDT]

Hello @jpmcb ! Good catch on the tests, I added a test related to the NO_COLOR env variable and the DisableColors parameter. Let me know if you see anything else that is missing.

On my end, I don't think anything is missing and I think all concerns above have been considered.

[catthehacker]

So I've just looked at the code out of curiosity. You should check for Linux terminals that don't support colouring ($TERM = dumb) But also, was that tested on Windows? With which versions it will be compatible? Did you consider using external dependency for colour output and/or terminal detection? (e.g.: https://github.com/mattn/go-colorable / https://github.com/mattn/go-isatty / https://github.com/fatih/color)

[umarcor]

@umarcor correct me if I'm wrong, but I think the problem around using viper is that when the help menu is being shown to the user (where the colors are used basically), the config file hasn't been parsed yet. The parsing happens with cobra.OnInitialize(initConfig) which only happens when the command is about to run basically.

@JulesDT. You are correct. If the command does not have a Run field, initConfig is not used.

[marckhouzam]

What shall we do with this colour PR? Reading the comment from @catthehacker, I don't know if this change will work on Windows, @JulesDT do you have the ability to try it? Maybe using an external package would be a good idea?

[catthehacker]

I don't know if this change will work on Windows

@marckhouzam Yes and no. It will work for people using Windows Terminal app but it will not work in default terminal.

[JulesDT]

Thanks for the screenshots and tests @catthehacker. If we are okay with using an external dependency, I can try to make the switch, I don't really have a Windows available for testing it.

Do we have any preference around which one to use?

[catthehacker]

Just wanted to add that I pointed to those packages as reference, I'm not well versed in using any of them and there might be better/more suitable libraries to use (or not using external deps at all).

Also I can test anything on current (Win10 2009), preview (dev builds) and previous (2004, 1909, 1903, Win8.1, Win8, Win7, etc.) Windows versions for you if you need.

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[stmcginnis]

I like the idea of this, but a little worried since it has such a broad impact on everyone using the library.

The biggest area of concern for me is Windows. As I understand it, right now the most common terminals are the legacy cmd.exe, powershell.exe, and the newer Windows Terminal. Of the three, only Windows Terminal will display colors by default. This will show what would appear to be garbage characters with the first two.

There are the options added to disable colorization, but for a Windows user running the default shell, it puts an extra burden on them to have to set the environment variable or add the argument to disable it.

I think it would be good to add some detection and automatically disable colorization if we can tell we are running somewhere that doesn't support it. Here is one way I've accomplished this in another project:

if runtime.GOOS == "windows" {
	// The newer Windows Terminal supports color, cmd and powershell do
	// not. Currently the only way to tell if you are running in WinTerm is
	// by the presence of a "WT_SESSION" environment variable.
	result = os.Getenv("WT_SESSION") != ""
}

There may be a better way to determine that, but of course the Windows terminals don't support the same variables and methods that Linux and macOS terminals do.

[umarcor]

@stmcginnis, note that Cygwin, MSYS2, Git for Windows, etc. are available on Windows. Those support ANSI colours. See the following discussion: https://github.com/tartley/colorama/issues/306. Hence, you are effectively proposing a reimplementation of colorama inside cobra. I believe it is desirable to offload that complexity to some other "golang color CLI" package, such as the ones suggested by @catthehacker above.

[stmcginnis]

I believe it is desirable to offload that complexity to some other "golang color CLI" package

Yep, I agree. Based on that, and the complexity of correctly detecting terminal capabilities, and the fact that this impacts all users of Cobra (a lot!) then I am -1 on this proposal. I don't think cobra should be handling color formatting and it should be left to another library to handle it.

[umarcor]

While I agree, I believe it would be interesting to provide a code example about how to achieve it. Maybe cobra can provide some hooks (an API) for users to plug their own (or third-party) colouring package.

[JulesDT]

@stmcginnis considering what you said, if we relied on https://github.com/fatih/color in ColoredName would that work for you? I'm happy to make that change, I still think Cobra would benefit a lot from allowing colors because this makes it so much easier to use in some tools.

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[ivanpirog]

ColoredCobra: https://github.com/ivanpirog/coloredcobra

ColoredCobra is a small library that allows you to colorize the text output of the Cobra library, making the console output look better.