Add custom sub generators to a Yeoman host generator

Usage no npm install needed!

<script type="module">
  import generatorSubgenext from '';



Gitter Build Status Coverage Status Dependency Status devDependency Status


npm install -g generator-subgenext

As this project doesn't make a whole lot of sense without a host generator, let's install generator-react-webpack for demo purposes. However, any Yeoman generator will do.

npm install -g generator-react-webpack@beta
mkdir -p ~/my-stuff/some-project && cd $_
yo react-webpack

Example: Let's try installing an external subgen: contrib-subgen-react-webpack-container.

# Change into the project directory and install the subgen globally or locally
cd ~/my-stuff/some-project && cd $_
npm install -g contrib-subgen-react-webpack-container

# Search for available subgens (note: see below how to put the hostgen's name into .yo-rc.json to skip typing it)
yo subgenext --host=react-webpack
# ✔ Found 1 sub generator for generator-react-webpack (4.0.1-1)
#   1  contrib-subgen-react-webpack-container  0.0.3  Host dependency satisfied: >=4.0.1-1  (not activated)

# Activate it
yo subgenext:activate container --host=react-webpack
# ? I will create a symlink
# from =>	/Users/sthzg/.nvm/versions/node/v6.2.2/lib/node_modules/contrib-subgen-react-webpack-container/generators/container
# in =>	/Users/sthzg/.nvm/versions/node/v6.2.2/lib/node_modules/generator-react-webpack/generators/container
# Confirm to proceed: Yes
# ✔ Activated container!

# Try it out
yo react-webpack:container demo --component --nostyle
# create src/components/DemoContainer.js
# create test/components/DemoContainerTest.js
# create src/components/Demo.js
# create test/components/DemoTest.js

# That was nice, get rid of it
yo subgenext:deactivate container
# ? I will remove this symlink
# => /Users/sthzg/.nvm/versions/node/v6.2.2/lib/node_modules/generator-react-webpack/generators/container
# Confirm to proceed: Yes
# ✔ Deactivated container!

The only interesting thing to take away from here is, how the contents of an external npm package become available as a sub generator in another, possibly third party host generator.

User Configuration


You can add subgen configuration in your .yo-rc.json.

Supported config props

if you omit the --host option on the command line it will fall back to using defaultHost

  "generator-subgenext": {
    "defaultHost": "foobar"

Authoring External Subgens


Authoring Configuration

Extgen authors can add a value for generator-subgenext into the extgen's package.json. Values inside this object will be considered for certain, supported authoring based config values.

Supported config props

A string added in namespace will be prepended while activating the extgen. This is helpful when you want to group subgens provided by your package under a namespace. If your package provides a subgen named container and your namespace is set to addons, the activated subgen will become available as yo host_gen:addons-container.


Feature vs. Implementation

It is often desirable to add custom sub generators (subgens) to an existing generator. Currently, you have the option to compose your own generator with others, but stacking generators on top of each other doesn't allow for modularity under one namespace.

Feature and implementation can be seen as two independent aspects. Maybe the proposed feature in general is useful but the implementation is poor or, less likely, the other way around ;)

We put a writeup of three approaches to achieve the goal to the Wiki Home, and The Fully Integrated Happy Path describes what probably would be the nicest way to go.

However, since we wanted to showcase this idea with a proof-of-concept that works without anyone (users or gen-authors) to change anything, we start by implementing it in a way that doesn't require changes to Yo core repositories or existing generators.

The rest of the readme deals w/ describing the current approach, shows how to setup the status quo on your local machine.



It often would be great to maintain one barebones umbrella generator and inject subgens from individual npm packages. With composeWith we have the oportunity to let different generators interact with one another during the Yeoman run loop, but semantically we always ship a new generator that provides its features under its own namespace.

The main aspect that this idea should enable is putting the subgenerator into the center of development and transforming the host generator to an open hub that the user can dock an arbitary number of subgens (core and contributed) onto. On top of this modularity it would allow different maintainers to contribute to different areas of a generator-domain while still publishing under the umbrella of the host generator.

Use Case 1

I use generator-x and and want an additional subgen, that is a) either specific to a current project or b) their maintainers simply do not wish to include. The subgen may need to interact with other subgens from the host generator (e.g. by invoking them programmatically and modifying the generated source after they ran)

Use Case 2

I provide a generator operating on a large and multifaceted domain. It becomes obvious that one monolithic package shouldn't provide sub-generators that cover all the options available (think of the Webpack and React ecosystem with its endless variaions of loaders, flux implementations, routers, etc.). Subgens on a plugin-base could ease this versatility by splitting responsibilities to a larger community that would still be able to ship under one unique generator namespace.

Use Case 3

I am working on experimental features of a generator that should already be accessible to early adopters, but are a) not ready to be merged into core or b) may still be denied adoption at all.


To invoke the test suite run:

npm run test