nx/docs/documentations/libraries.md

Creating a Lib

Adding new libs to an Nx Workspace is done by using the Angular CLI generate command, just like adding a new app.

ng generate lib mylib
ng generate library mylib # same thing

This will create a new lib, will place it in the libs directory, and will configure the angular.json and nx.json files to support the new lib.

Available options

Run ng generate lib --help to see the list of available options:

usage: ng generate lib <name> [options]
options:
  --directory
    A directory where the app is placed
  --dry-run (-d)
    Run through without making any changes.
  --force (-f)
    Forces overwriting of files.
  --lazy
    Add RouterModule.forChild when set to true, and a simple array of routes when set to false.
  --parent-module
    Update the router configuration of the parent module using loadChildren or children, depending on what `lazy` is set to.
  --prefix (-p)
    The prefix to apply to generated HTML selector of components.
  --publishable
    Generate a simple TS library when set to true.
  --routing
    Add router configuration. See lazy for more information.
  --skip-package-json
    Do not add dependencies to package.json.
  --skip-ts-config
    Do not update tsconfig.json for development experience.
  --tags
    Add tags to the library (used for linting)

Most of these options are identical to the ones supported by the default CLI library, but the following are new or different: directory, routing, lazy, parent-module, publishable, and tags.

• ng generate lib mylib --directory=myteam will create a new application in libs/myteam/mylib.
• ng generate lib mylib --routing will configure the lib's NgModule to wire up routing to be loaded eagerly.
• ng generate lib mylib --routing --lazy will configure the lib's NgModule to wire up routing to be loaded lazily.
• ng generate lib mylib --routing --parent-module=apps/myapp/src/app/app.module.ts will configure the lib's NgModule to wire up routing and will configure app.module.ts to load the library.
• ng generate lib mylib --routing --lazy --parent-module=apps/myapp/src/app/app.module.ts will configure the lib's NgModule to wire up routing and will configure app.module.ts to load the library.
• ng generate lib mylib --publishable will generate a few extra files configuring for ng-packagr. You can then run ng build mylib to create an npm package you can publish to a npm registry. This is very rarely needed when developing in a monorepo. In this case the clients of the library are in the same repository, so no packaging and publishing step is required.
• ng generate lib mylib --tags=shared,experimental will annotate the created lib with the two tags, which can be used for advanced code analysis. Read more below.

Note when creating lazy-loaded libraries, you need to add an entry to the tsconfig.app.json file of the parent module app, so TypeScript knows to build it as well:

{
  . . .

  "include": [
      "**/*.ts"
      /* add all lazy-loaded libraries here: "../../../libs/my-lib/index.ts" */

      , "../../../libs/mymodule/src/index.ts"
  ]
}

In most cases, Nx will do it by default. Sometime, you need to manually add this entry.

This is great, but is not sufficient to enable the monorepo-style development. Nx adds an extra layer of tooling to make this possible.