projen synthesizes project configuration files such as package.json, tsconfig.json, .gitignore, GitHub Workflows, eslint, jest, etc. from a well-typed definition written in JavaScript.

As opposed to existing templating/scaffolding tools, projen is not a one-off generator. Synthesized files should never be manually edited (in fact, projen enforces that). To modify your project setup, users interact with rich strongly-typed class and execute projen to update their project configuration files.

By defining a custom project type and using projen in multiple repositories, it's possible to update configuration files and CI/CD workflows across dozens (or hundreds!?) of projects.

Check out this talk about projen from its creator.

Getting Started

projen doesn't need to be installed. You will be using npx to run projen which takes care of all required setup steps.

To create a new project, run the following command and follow the instructions:

$ mkdir my-project
$ cd my-project
$ npx projen new PROJECT-TYPE
🤖 Synthesizing project...
...

Project types

Currently supported project types (use npx projen new without a type for a full list):

Built-in: (run npx projen new <type>)

• awscdk-app-java - AWS CDK app in Java.
• awscdk-app-py - AWS CDK app in Python.
• awscdk-app-ts - AWS CDK app in TypeScript.
• awscdk-construct - AWS CDK construct library project.
• cdk8s-app-py - CDK8s app in Python.
• cdk8s-app-ts - CDK8s app in TypeScript.
• cdk8s-construct - CDK8s construct library project.
• cdktf-construct - CDKTF construct library project.
• java - Java project.
• jsii - Multi-language jsii library project.
• nextjs - Next.js project using JavaScript.
• nextjs-ts - Next.js project using TypeScript.
• node - Node.js project.
• project - Base project.
• python - Python project.
• react - React project using JavaScript.
• react-ts - React project using TypeScript.
• typescript - TypeScript project.
• typescript-app - TypeScript app.

External: (run npx projen new --from <type>)

• projen-github-action-typescript - GitHub Action in TypeScript project.

Use npx projen new PROJECT-TYPE --help to view a list of command line switches that allows you to specify most project options during bootstrapping. For example: npx projen new jsii --author-name "Jerry Berry".

The new command will create a .projenrc.js file which looks like this for jsii projects:

const { JsiiProject } = require('projen');

const project = new JsiiProject({
  authorAddress: "[email protected]",
  authorName: "Elad Ben-Israel",
  name: "foobar",
  repository: "https://github.com/eladn/foobar.git",
});

project.synth();

This program instantiates the project type with minimal setup, and then calls synth() to synthesize the project files. By default, the new command will also execute this program, which will result in a fully working project.

Once your project is created, you can configure your project by editing .projenrc.js and re-running npx projen to synthesize again.

The files generated by projen are considered an "implementation detail" and projen protects them from being manually edited (most files are marked read-only, and an "anti tamper" check is configured in the CI build workflow to ensure that files are not updated during build).

For example, to setup PyPI publishing in jsii projects, you can use publishToPypi option:

const project = new JsiiProject({
  // ...
  publishToPypi: {
    distName: "mydist",
    module: "my_module",
  }
});

Run:

npx projen

And you'll notice that your package.json file now contains a python section in its jsii config and the GitHub release.yml workflow includes a PyPI publishing step.

We recommend to put this in your shell profile, so you can simply run pj every time you update .projenrc.js:

alias pj='npx projen'

Most projects come with an assortment of tasks that handle various development activities, from compiling to publishing. Tasks can be and composed together, and can be run as local commands or turned into GitHub workflows. You can list all tasks with npx projen --help:

$ npx projen --help
projen [command]

Commands:
  projen new [PROJECT-TYPE-NAME] [OPTIONS]  Creates a new projen project
  projen clobber                            hard resets to HEAD of origin and cleans the local repo
  projen compile                            Only compile
  projen test                               Run tests
  projen build                              Full release build (test+compile)
  projen upgrade                            upgrade dependencies (including projen)
...

The build task is the same task that's executed in your CI builds. It typically compiles, lints, tests and packages your module for distribution.

Shell Completions

If installed as a global package, projen includes rich shell tab-completion support. To enable this in your shell, run:

# Bash
projen completion >> ~/.bashrc

# ZSH
projen completion >> ~/.zshrc

Features

Some examples of features built-in to project types:

• Fully synthesize package.json
• Standard npm scripts like compile, build, test, package
• eslint
• Jest
• jsii: compile, package, api compatibility checks, API.md
• Bump & release scripts with CHANGELOG generation based on conventional commits
• Automated PR builds
• Automated releases to npm, maven, NuGet and PyPI
• Automated dependency upgrades
• Mergify configuration
• LICENSE file generation
• gitignore + npmignore management
• Node "engines" support with coupling to CI build environment and @types/node
• Anti-tamper: CI builds will fail if a synthesized file is modified manually

Documentation

For documentation including examples and a full API reference, visit https://projen.io/.

Ecosystem

projen takes a "batteries included" approach and aims to offer dozens of different project types out of the box (we are just getting started). Think projen new react, projen new angular, projen new java-maven, projen new awscdk-typescript, projen new cdk8s-python (nothing in projen is tied to javascript or npm!)...

Adding new project types is as simple as submitting a pull request to this repo and exporting a class that extends projen.Project (or one of its derivatives). Projen automatically discovers project types so your type will immediately be available in projen new.

Projects in external modules

projen is bundled with many project types out of the box, but it can also work with project types and components defined in external jsii modules (the reason we need jsii is because projen uses the jsii metadata to discover project types & options in projen new).

Say we have a module in npm called projen-vuejs which includes a single project type for vue.js:

$ npx projen new --from projen-vuejs

If the referenced module includes multiple project types, the type is required. Switches can also be used to specify initial values based on the project type APIs. You can also use any package syntax supported by yarn add like [email protected], file:/path/to/local/folder, [email protected]/awesome/projen-vuejs#1.2.3, etc.

$ npx projen new --from projen-vuejs@^2 vuejs-ts --description "my awesome vue project"

Under the hood, projen new will install the projen-vuejs module from npm (version 2.0.0 and above), discover the project types in it and bootstrap the vuejs-ts project type. It will assign the value "my awesome vue project" to the description field. If you examine your .projenrc.js file, you'll see that projen-vuejs is defined as a dev dependency:

const { VueJsProject } = require('projen-vuejs');

const project = new VueJsProject({
  name: 'my-vuejs-sample',
  description: "my awesome vue project",
  // ...
  devDeps: [
    'projen-vuejs'
  ]
});

project.synth();

Roadmap

See Vision.

FAQ

Do I have to write my configuration in JavaScript?

Not at all! JavaScript is the default, but it's also possible to write it in Java, Python, TypeScript, or even JSON. This is made possible by the jsii library which allows us to write APIs once and generate libraries in several languages. You can choose a different language by passing the --projenrc-ts, --projenrc-py, --projenrc-java, or --projenrc-json flags when running projen new.

Note: using a .projenrc.json file to specify configuration only allows accessing a subset of the entire API - the options which are passed to the constructor of each project type.

How does projen work with my IDE?

projen has an unofficial VS Code extension. Check it out!

Community

The projen community can be found within the #projen channel in the cdk.dev community Slack workspace.

Virtual Meetup

• Thursday June 30, 2022
• 1-2pm America/New_York (EDT)
• CFP a Google Form
• CFP Closes Saturday April 30, 2022
• Hosted on Zoom

Contributions

Contributions of all kinds are welcome! Check out our contributor's guide and our code of conduct.

For a quick start, check out a development environment:

$ git clone [email protected]:projen/projen
$ cd projen
$ yarn
$ yarn watch # compile in the background

Thanks goes to these wonderful people (emoji key):