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.

Install

npm install -g plop

Setup

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 two main functions (addHelper, setGenerator). addHelper is directly passed through 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();
	});
};

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'
		}]
	});
};

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.
A custom action can be synchronous or asynchronous (by returning a promise).
A message can be returned from the function and will be reported 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 an Actions Function

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

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;
		}
	});
};

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 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 creating a new controller shouldn't mean copying another controller and stripping it of everything that is unique to it.

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. So that got me thinking... you know, what I really want is for these generators to be part of the codebase. Plop does that for you.

brock/plop