hygen is the simple, fast, and scalable code generator that lives in your project.

Quick Start

Install hygen:

$ npm i -g hygen

Want to try an example generator?

$ hygen example-prompt new

? What's your message? welcome

Loaded templates: src/templates
       added: hygen-examples/mailers/unnamed.js
       added: hygen-examples/mailers/hello/html.ejs
       added: hygen-examples/mailers/hello/subject.ejs
       added: hygen-examples/mailers/hello/text.ejs
      inject: hygen-examples/mailers/hello/html.ejs

This will generate content into the current working directory in hygen-example.

Here's a few more ways to play with the demo templates:

# generate all required worker files, with a name variable
$ hygen example-prompt new --name reporter


# generate one specific file
# the 'example' generator template layout is:
# example/
#   new/
#     mailer.ejs.t  
#     templates_html.ejs.t
#     templates_subject.ejs.t  
#     templates_text.ejs.t  
#     z_inject.ejs.t
#
$ hygen example-prompt new:mailer --name reporter


# generate all files that correspond to a regular expression
$ hygen example-prompt 'new:.*html' --name reporter

Want to start using hygen in your own project?

Start Using It

$ hygen init self
Loaded templates: src/templates
       added: _templates/generator/with-prompt/hello.ejs.t
       added: _templates/generator/with-prompt/prompt.ejs.t
       added: _templates/generator/new/hello.ejs.t

$ hygen generator new my-new-generator --name hello

Loaded templates: _templates
       added: _templates/hello/new/hello.ejs.t

This will create a project-local _templates folder for your at your source root, with a sample generator.

You can go ahead and edit hello.ejs.t. See below how templates are composed.

Templates

This is what we have right now:

_templates/
  hello/
    new/
      hello.ejs.t

And here's our hello.ejs.t template:

---
to: app/hello.js
---
const hello = `
Hello!
This is your first hygen template.

Learn what it can do here:

https://github.com/jondot/hygen
`

console.log(hello)

Let's turn it into a react component generator, and let's say all our component live in src/components.

First, let's rename hello:

$ mv _templates/{hello,component}

In hygen folder structure is command structure. Now let's compose our component template:

---
to: src/components/<%= name %>.js
---
import React, { PureComponent } from 'react'
class <%= Name %> extends Component {
  render(){
    return <div>replace me!</div>
  }
}
export default <%= Name %>

Finally let's enjoy our new generator!

$ hygen component new --name icon

Loaded templates: _templates
       added: src/components/icon.js

Variables

You might have noticed Name in the previous template. There are two ways to supply hygen templates with variables.

Arguments

For unattended generation, it's best to use arguments:

$ hygen email new --name foobar --message hello --type 8

All double-dash (--) arguments become available to you in your templates, so this will populate them.

Hi <%= name %>,
<%= message %>.

You've been selected to group <%= type %>.

Prompts

If you prefer some of your generators to be interactive (you can mix and match), you can use prompts.

Per generator, you have the option to include a prompt.js file, that will collect all variables from the user for this given generator.

_templates/
  email/
    new/
      prompt.js    <-- your prompt file!
      html.ejs.t

The format is based on inquirer so hopefully, nothing new to you.

A Different Kind of a Generator

hygen is a scalable generator. It has developer and team ergonomics as first priority.

It avoids "blessed" or dedicated projects that codifies code generation, which before you know it, become a product you build, needs testing, CI, separate pull request reviews, and ultimately sucks up your time and becomes this super hated thing no one likes to touch anymore.

Plus, since they are not the product you are building they become notoriously hard to reason about.

Scratch Your Own Itch

Because hygen templates live in your project, it cuts the time from having an itch for generating code (Redux, anyone?) in your current project to code generated with it and others benefiting from it.

Let's go over why hygen is different. Here's our example from before:

_templates/
  component/
    new/
      hello.ejs.t

Batteries Included

hygen helps you make new generators and templates.

Setup for a new project:

$ cd new-project
$ hygen init self

Make your first generator:

$ hygen generator new --name my-generator

and a generator that asks you questions:

$ hygen generator with-prompt --name my-generator

Template Locality

hygen picks up a local _templates folder at any folder level of your project you're working from.

This is important because:

• Templates are project-local. A git clone of the project fetches all generators as well.
• Different generators can be tucked in different parts of the project, making it contextual.
• Template locality is scalable; different teams can maintain different generators.
• When you change your code, you can make changes in the template and pack in the same commit, to be reviewed and merged in the same PR (as opposed to installing different "plugins" or different templates from out-of-repo places).

And yet, if you don't like project-local templates:

• You can have a global _templates folder (maybe a central git repo you maintain?) by populating an environment variable HYGEN_TMPLS
• You can build a custom generator of your own with hygen at its core, and pack your own templates with it.

Folder Structure is Command Structure

The templates folder structure maps directly to the command structure:

$ hygen worker new --name jobrunner

For this command, hygen worker new maps to _templates/worker/new and all files within worker/new are rendered.

Template parameters are given with --flag VALUE, as many as you'd like. In this example we've set a parameter named name to the value jobrunner.

Subcommands

A subcommand is a file inside a your folder structure. So if the structure is this:

_templates/
    worker/
      new/
        index.html.ejs
        setup.html.ejs

And you only want setup, you can run:

$ hygen worker new:setup

You can also use the subcommand as a regular expression so, these will do the same:

$ hygen worker new:se

$ hygen worker new:se.*

Frontmatter for Decluttering

Here's how a template looks like (in our example, index.ejs.t). Templates bodies are ejs:

---
to: app/workers/<%=name%>.js
---

class <%= h.capitalize(name) %> {
    work(){
        // your code here!
    }
}

The first part of the template is a front matter, idea borrowed from Markdown, this is the metadata part of a hygen template and is part of the reason of why your templates will feel more lightweight and flexible.

All frontmatter metadata are also run through the template engine so feel free to use variables in the frontmatter as you wish.

There's one required metadata variable: to. to points to where this file will be placed (folders are created as needed).

Addition or Injection

By default templates are 'added' to your project as a new target file, but you can also choose to inject a template into an existing target file.

For this to work, you need to use inject: true with the accompanied inject-specific props.

---
to: package.json
inject: true
after: dependencies
skip_if: react-native-fs
---
"react-native-fs":"*",

This template will add the react-native-fs dependency into a package.json file, but it will not add it twice (see skip_if).

Here are the available mutually-exclusive options for where to inject at:

• before | after - a regular expression / text to locate. The inject line will appear before or after the located line.
• prepend | append - add a line to start or end of file respectively.
• line_at - add a line at this exact line number.

You can guard against double injection:

• skip_if - a regular expression / text. If exists injection is skipped.

Build Your Own

hygen is highly embeddable. You should be able to use it by simply listing it as a dependency and having this kind of workflow in your binary.

const { runner } = require('hygen')
const path = require('path')
const defaultTemplates = path.join(__dirname, 'templates')

runner(process.argv.slice(2), {
  templates: defaultTemplates,
  cwd: process.cwd(),
  logger: console,
  debug: !!process.env.DEBUG
})

Development

The Hygen codebase has a functional style where possible. This is because naturally, it feeds parameters and spits out files. Try to keep it that way.

Running hygen locally, rigged to your current codebase (note the additional -- to allow passing flags)

$ yarn hygen -- mailer new --name foobar

Running tests in watch mode:

$ yarn watch

Metaverse Testing

The easiest way to make an impact is to use the built-in metaverse tests suite, and then add the tests here.

The idea here is to copy templates from any project that use hygen and to test that it works at all times. This keeps tabs on the hygen universe / ecosystem (nicknamed metaverse) and makes sure this test suite breaks before hygen clients break.

Internal Testing

Testing hygen internally is also easy. We provide an abstraction layer (Note here be dragons) for easy end-to-end testing with a virtual file system.

The rest of the tests are here

Start Up Speed Testing

Many generators become painfully slow to use as the thing you want to generate grow (because, real life),

This is why hygen takes speed as a first class citizen, and sports a dedicated start-up timing suite:

$ yarn test:require

In addition, thought is given to which dependencies to take in, how their file structure fan out and what kind of disk access (due to require) would hygen ultimately have when we run it. This is recorded with every test run.

Bundling a single file was evaluated (and the infrastructure is still there, using webpack) and wasn't faster than what we have right now.

Contributing

Fork, implement, add tests, pull request, get my everlasting thanks and a respectable place here :).

Thanks:

To all Contributors - you make this happen, thanks!

Copyright

Copyright (c) 2018 Dotan Nahum @jondot. See LICENSE for further details.