Plop

Micro-generator framework that makes it easy for an entire team to create files with a level or uniformity.

Plop is essentially glue code between inquirer prompts and handlebar templates. You can also add your own handlebar helper methods and use them in your templates.

Getting Started

1. Install plop globally

$ npm install -g plop

2. Install plop in your project's devDependencies

$ npm install --save-dev plop

3. Create a plopfile.js at the root of your project

module.exports = function (plop) {
	// create your generators here
	plop.setGenerator('basics', {
		description: 'this is a skeleton plopfile',
		prompts: [],
		actions: []
	});
};

Anatomy of a Plop Generator

The main parts of a plop generator are the plop file (plopfile.js) and the templates. Templates can either be inline, or in separate files.

A basic plop file starts its life as a lowly node module that exports a function that accepts the plop object.

module.exports = function (plop) {};

The plop object offers four main functions (addHelper, addPartial, addPrompt, setGenerator).

plop.addHelper(name, helper)

name {String}
helper {Function}

addHelper directly corresponds to the handlebars method registerHelper. So if you are familiar with handlebars helpers, then you already know how this works.

module.exports = function (plop) {
	plop.addHelper('upperCase', function (text) {
		return text.toUpperCase();
	});

	// or in es6/es2015
	plop.addHelper('upperCase', (txt) => txt.toUpperCase());
};

plop.addPartial(name, template)

name {String}
template {String}

addPartial directly corresponds to the handlebars method registerPartial. So if you are familiar with handlebars partials, then you should be good to go here as well.

module.exports = function (plop) {
	plop.addPartial('fullName', '{{ firstName }} {{ lastName }}');
};

plop.addPrompt(name, inquirerPlugin)

name {String}
inquirerPlugin {Constructor}

addPrompt is a shortcut method to inquirer's prompt.registerPrompt function. If inquirer's built in prompt types don't quite cut the mustard for you, you can write your own or look at this list of custom prompts that other plop users have found useful.

module.exports = function (plop) {
	plop.addPrompt('directory', require('inquirer-directory'));
};

Next we need to setup a generator using plop.setGenerator

plop.setGenerator(name, config);

name {String}
config {Object}

The config object needs to include prompts and actions (description is optional). The prompts array is passed to inquirer. The actions array is a list of actions to take (described in greater detail below)

module.exports = function (plop) {
	plop.setGenerator('test', {
		description: 'this is a test',
		prompts: [{
			type: 'input',
			name: 'name',
			message: 'What is your name?',
			validate: function (value) {
				if ((/.+/).test(value)) { return true; }
				return 'name is required';
			}
		}],
		actions: [{
			type: 'add',
			path: 'folder/{{dashCase name}}.txt',
			templateFile: 'templates/temp.txt'
		}]
	});
};

The Actions Array

The plop.setGenerator config object includes an array of actions to take. There are two types of actions you can include (add and modify). Both types of actions require a path to take action on (all paths are based on the location of the plopfile), and a template to use.

Let's start with the simpler of the 2 actions, add.

Add (Action)

The add action is used to (you guessed it) add files to your project. The path property is a handlebars template that will be used to create the file by name. The file contents will be determined by the template or templateFile property. As you've probably guessed, the template property is used for an inline template while the templateFile is a path to the template stored in a file somewhere else in the project. I suggest keeping your template files in a plop-templates folder at the root of the project.

Modify (Action)

The modify action is similar to add, but the main difference is that it will use a pattern property to find/replace text in the file specified by the path property. The pattern property should be a RegExp and capture groups can be used in the replacement template using $1, $2, etc. More details on modify can be found in the example folder.

Custom (Action Function)

The Add and Modify actions will take care of almost every case that plop is designed to handle. However, plop does offer custom actions for the node/js guru. A custom action is a function that is provided in the actions array.

The custom action will be executed with the question responses as its only parameter.
Plop will wait for the custom action to complete before executing the next action.
The function must let plop known what’s happening through the return value. If you return a Promise, we won’t start other actions until the promise resolves. If you return a message (anything else except undefined), we know that the action is done. We’ll report the message in the status of the action.
A custom action fails if the promise is rejected, or the function throws an Exception

See the example plopfile for a sample synchronous custom action.

Using a Dynamic Action Array

Alternatively, actions can itself be a function that takes responses data as a parameter and should return the actions array.

This allows you to adapt actions to provided answers:

module.exports = function (plop) {
	plop.setGenerator('test', {
		description: 'this is a test',
		prompts: [{
			type: 'input',
			name: 'name',
			message: 'What is your name?',
			validate: function (value) {
				if ((/.+/).test(value)) { return true; }
				return 'name is required';
			}
		},{
			type: 'confirm',
			name: 'wantTacos',
			message: 'Do you want tacos?'
		}],
		actions: function(data) {
			var actions = [];

			if(data.wantTacos) {
				actions.push({
					type: 'add',
					path: 'folder/{{dashCase name}}.txt',
					templateFile: 'templates/tacos.txt'
				});
			} else {
				actions.push({
					type: 'add',
					path: 'folder/{{dashCase name}}.txt',
					templateFile: 'templates/burritos.txt'
				});
			}

			return actions;
		}
	});
};

Other Plop Methods/Attributes

These methods and attributes are available off the plop object. They are mostly used by plop internally, but some can come in handy when you're doing something a little more custom.

plop.renderString(template, data)

template {String}
data {Object}

Renders the handlebars template using the data passed in. Returns the rendered template.

plop.getGenerator(name)

name {String}

Gets a generator config object by name.

plop.getGeneratorList()

Gets an array of generator names and descriptions.

plop.loadPlops()

plopsFolder {String}

Loops through the JavaScript files contained within plopsFolder, requiring each one and passing the exported method the plop instance. This allows for better organization of plop files.

// plopfile.js
module.exports = function(plop) {
	plop.loadPlops('./plops');
};

// ./plops/my-generator.js
module.exports = function(plop) {
	plop.setGenerator('my-generator', {
		// ...
	});
};

plop.getPlopfilePath

Returns the absolute path to the plopfile in use.

plop.inquirer

The instance of inquirer that plop is using internally.

plop.handlebars

The instance of handlebars that plop is using internally.

Baked-In Helpers

There are a few helpers that I have found useful enough to include with plop. They are mostly case modifiers, but here is the complete list.

camelCase: changeFormatToThis
snakeCase: change_format_to_this
dashCase/kabobCase: change-format-to-this
dotCase: change.format.to.this
pathCase: change/format/to/this
properCase/pascalCase: ChangeFormatToThis
lowerCase: change format to this
sentenceCase: Change format to this,
constantCase: CHANGE_FORMAT_TO_THIS
titleCase: Change Format To This
pkg: look up a property from a package.json file in the same folder as the plopfile.

Usage

Once plop is installed, and you have created a generator, you are ready to run plop from the terminal. Running plop with no parameters will present you with a list of generators to pick from. You can also run plop [generatorName] to trigger a generator directly.

Why?

Because when you create your boilerplate separate from your code, you naturally put more time and thought into it.

Because saving your team (or yourself) 5-15 minutes when creating every route, component, controller, helper, test, view, etc... really adds up.

Because context switching is expensive and saving time is not the only benefit to automating workflows

Why Not Yeoman?

Yeoman is great and it does a fantastic job of scaffolding out an initial codebase for you. However, the initial codebase is just the beginning. I believe the true benefit to generators is not realized by saving a developer 40 hours in the beginning, but by saving a team days of work over the life of the project. Yes, yeoman has sub generators that do a similar job. However, if you're like me, you will continually tweak structure and code throughout the project till the sub generators that came built into your yeoman seed are no longer valid. These structures change as requirements change and code is refactored. Plop allows your generator code to live INSIDE your project and be versioned right along with the code it generates.

If you already have another generator that your organization uses and loves, use it :-). If you don't, try plop. It will make your code more consistent, save you lots of time, and (if you've read this far) you already know how to use it.

tkambler/plop