Making your own tasks

Create either ~/.mrm/<TASK>/index.js or ~/dotfiles/mrm/<TASK>/index.js. If <TASK> is the same as one of the default tasks your task will override the default one.

Tip: Tasks could be packaged into presets if you want to share them, see Making presets.

Basic tasks

The simplest task could look like this:

// Mrm module to work with new line separated text files
const { lines } = require('mrm-core');
module.exports = function task() {
// Read .gitignore if it exists
lines('.gitignore')
// Add lines that do not exist in a file yet,
// but keep all existing lines
.add(['node_modules/', '.DS_Store'])
// Update or create a file
.save();
};
module.exports.description = 'Adds .gitignore';

Tasks can also be async by adding the async keyword or returning a Promise.

async function task() {}
// or
function task() {
return new Promise(() => {});
}

Tasks with dependencies

If your tasks have dependencies (such as mrm-core) you should initialize the mrm folder as an npm module, and install your dependencies there:

cd ~/.mrm # or cd ~/dotfiles/mrm
npm init -y
npm install --save mrm-core

Tip: mrm-core is a library of utility helpers for writing Mrm tasks, that has functions to work with common config files (JSON, YAML, INI, Markdown), npm dependencies, etc.

Tasks with utility helpers (mrm-core) and parameters

Let’s take a look at a more complex task.

// Import utility helpers (could use any npm package here)
const {
// JSON files
json,
// package.json
packageJson,
// New line separated text files
lines,
// Install npm packages
install
} = require('mrm-core');
// task() function gets task parameters object as the first argument
// (see `module.exports.parameters` at the end of the file)
module.exports = function task({ eslintPreset }) {
// Define packages to install.
const packages = ['eslint'];
// Append custom eslint-config in case it's defined
if (eslintPreset !== 'eslint:recommended') {
packages.push(`eslint-config-${eslintPreset}`);
}
// Create or load .eslintignore, and set basic ignores
lines('.eslintignore')
.add(['node_modules/'])
.save();
// Create or load package.json
const pkg = packageJson();
pkg
// Set linting script
.setScript('lint', 'eslint . --cache --fix')
// Set pretest script
.prependScript('pretest', 'npm run lint')
// Save changes to package.json
.save();
// Create or load .eslintrc
const eslintrc = json('.eslintrc');
// Use Babel parser if the project depends on Babel
if (pkg.get('devDependencies.babel-core')) {
const parser = 'babel-eslint';
packages.push(parser);
eslintrc.merge({ parser });
}
// Configure ESlint preset, if set (defaults to eslint:recommended)
if (eslintPreset) {
eslintrc.set('extends', eslintPreset);
}
// Save changes to .eslintrc
eslintrc.save();
// Install new npm dependencies
install(packages);
};
// Define task configuration (see "Configuration prompts" section below for details)
module.exports.parameters = {
// Follows Inquirer.js questions format.
eslintPreset: {
// input, number, confirm, list, rawlist, expand, checkbox, password, editor
type: 'input',
message: 'ESLint preset to use as basis',
default: 'eslint:recommended'
}
};
// Description to show in the task list
module.exports.description = 'Adds ESLint';

Have a look at mrm-core docs for more utility helpers, and the default tasks for examples.

Configuration prompts

Configuration prompts allows you to configure tasks, by specifying options in the config file, via command line parameters, or via an interactive prompt questions.

Here’s a basic configuration prompt:

module.exports.parameters = {
eslintPreset: {
type: 'input',
message: 'ESLint preset to use as basis',
default: 'eslint:recommended'
}
};

Tip: Mrm supports more complex prompts too — have a look at Inquirer.js docs.

We pass all parameters to Inquirer.js, unless they have the config type, which means this parameter could only be difined via the config file. Use it for complex data, like objects.

module.exports.parameters = {
indent: {
type: 'config',
default: 'tab'
}
};

The default can be a literal value, like in the example above, or a function that receives an object with config values and command line overrides:

module.exports.parameters = {
spaces: {
type: 'input',
message: 'Number of spaces for tab stop',
default(options) {
return options.input || Math.round(Math.random() * 10);
}
}
};

This is different from the default Inquirer.js behavior and works consistently in Mrm’s interactive and non-interactive modes.

Use the validate() method to make a parameter required:

module.exports.parameters = {
eslintPreset: {
type: 'input',
message: 'ESLint preset to use as basis',
validate(value) {
return value ? true : 'eslintPreset is required';
}
}
};

In this case the only ways to override the default walue are a config file, or a command line parameter.

Migrating from the legacy parameters to Inquirer.js

Calling .defaults(), .required() and .values() on the parameters object has been deprecated.

module.exports = function task(config) {
const {
indent,
prettierPattern,
prettierOptions,
prettierOverrides
} = config
.defaults({
indent: 'tab'
})
.values();
// ...
};

Now, Mrm passes parameters to the task function as a plain object:

module.exports = function task({
indent,
prettierPattern,
prettierOptions,
prettierOverrides
}) {
// ...
};

Parameters are described using an Inquirer.js object:

module.exports.parameters = {
indent: {
type: 'input',
message: 'Choose indentation style (tabs or number of spaces)',
default: 'tab',
choices: ['tab', 2, 4, 8]
},
prettierPattern: {
type: 'input',
message: 'Enter Prettier file glob pattern',
default: 'auto'
},
prettierOptions: {
type: 'config'
},
prettierOverrides: {
type: 'config'
}
};

See the previous section for more examples.

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