@poppinss/colors

Colors

Wrapper on top of Kleur with support for testing color calls.

This module is a wrapper on top of Kleur to make it easier to test the output generated by the kleur API. The API exposed is 100% the same as kleur.

Table of contents

• Why use this module?
  • The problem
  • Our solution
  • How to use it in real world?
• Installation

Why use this module?

This module attempts to solve two specific problems.

• Make it easier to test strings using kleur color transformations.
• Provide a alternate implementation for non-tty terminals.

The problem

Let's imagine you are writing a test to ensure that function dummy outputs an error message to the console in certain situation.

import { bgRed } from 'kleur'

function dummy() {
  if (someCondition) {
    console.log(bgRed().white('Error'))
  }
}

You may attempt to test the output as follows:

const output = trapConsoleMessage()
dummy()

assert.equal(output, 'Error') // fails

The assertion will fail, since the string Error has ansi sequences applied to it to make it colorful.

To workaround this behavior, you can use a module like strip-ansi to string the ansi sequences and write assertions against the plain string.

import stripAnsi from 'strip-ansi'

const output = trapConsoleMessage()
dummy()

assert.equal(stripAnsi(output), 'Error') // passes

Now, your assertions are passing, but there is no way to know which kleur transformations were applied to the string.

Our solution

Instead of relying on strip-ansi, we ship with an alternative implementation of kleur, which doesn't apply ansi sequences at first place. Example:

import { FakeColors } from '@poppinss/colors'
const colors = new FakeColors()

const output = colors.bgRed().white('Error')
assert.equal(output, 'bgRed(white(Error))') // passes

Notice the difference in the output? Instead of applying the background color and the text color. We wrap the value inside the applied transformations and return it back as a string.

How to use it in real world?

At AdonisJS, we rely on the NODE_ENV environment variable to decide the implementation to choose. For example:

import { FakeColors, Colors } from '@poppinss/colors'

export default const colors = process.env.NODE_ENV === 'testing'
  ? new FakeColors()
  : new Colors()

Now, inside the entire codebase, we import the above helper for colorizing output.

import colors from './helpers/colors'
colors.red('Error')

Installation

Install the package from npm registry as follows:

npm i @poppinss/colors

# yarn
yarn add @poppinss/colors

and then use it as follows:

import { FakeColors, Colors, Raw } from '@poppinss/colors'

// Real implementation
const colors = new Colors()

// Use for testing
const fakeColors = new FakeColors()

// When running in non-tty terminals
const rawColors = new Raw()