Angular

Using a Stencil built web component collection within an Angular CLI project is a two-step process. We need to:

Include the CUSTOM_ELEMENTS_SCHEMA in the modules that use the components.
Call defineCustomElements() from main.ts (or some other appropriate place).

Including the Custom Elements Schema

Including the CUSTOM_ELEMENTS_SCHEMA in the module allows the use of the web components in the HTML markup without the compiler producing errors. This code should be added into the AppModule and in every other modules that use your custom elements. Here is an example of adding it to AppModule:

import { BrowserModule } from '@angular/platform-browser';
import { CUSTOM_ELEMENTS_SCHEMA, NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';

import { AppComponent } from './app.component';

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule, FormsModule],
  bootstrap: [AppComponent],
  schemas: [CUSTOM_ELEMENTS_SCHEMA],
})
export class AppModule {}

The CUSTOM_ELEMENTS_SCHEMA needs to be included in any module that uses custom elements.

Calling defineCustomElements

A component collection built with Stencil includes a main function that is used to load the components in the collection. That function is called defineCustomElements() and it needs to be called once during the bootstrapping of your application. One convenient place to do this is in main.ts as such:

import { enableProdMode } from '@angular/core';
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';

import { AppModule } from './app/app.module';
import { environment } from './environments/environment';

// Note: loader import location set using "esmLoaderPath" within the output target config
import { defineCustomElements } from 'test-components/loader';

if (environment.production) {
  enableProdMode();
}

platformBrowserDynamic().bootstrapModule(AppModule)
  .catch(err => console.log(err));
defineCustomElements();

Edge and IE11 polyfills

If you want your custom elements to be able to work on older browsers, you should add the applyPolyfills() that surround the defineCustomElements() function.

import { applyPolyfills, defineCustomElements } from 'test-components/loader';
...
applyPolyfills().then(() => {
  defineCustomElements()
})

Accessing components using ViewChild and ViewChildren

Once included, components could be referenced in your code using ViewChild and ViewChildren as in the following example:

import {Component, ElementRef, ViewChild} from '@angular/core';

import 'test-components';

@Component({
    selector: 'app-home',
    template: `<test-components #test></test-components>`,
    styleUrls: ['./home.component.scss'],
})
export class HomeComponent {

    @ViewChild('test') myTestComponent: ElementRef<HTMLTestComponentElement>;

    async onAction() {
        await this.myTestComponent.nativeElement.testComponentMethod();
    }
}

Bindings

Angular has a pretty good story for integration with web components but there are a few issues with the developer experience. With bindings, the web components get wrapped in an Angular component and then immediately become available as Angular Components. Some of the advantages of doing this are that you get types for your components and you also get the ability to use ngmodel on inputs. Your developers then consuming your web components from Angular applications import an actual Angular Library and to them it feels as though they are interacting with Angular components.

Install

npm install @stencil/angular-output-target --save-dev

Stencil Config setup

To make use of the AngularOutputPlugin first import it into your stencil.config.ts file. Then add it as an OutputTarget.

import { Config } from '@stencil/core';
import { angularOutputTarget, ValueAccessorConfig } from '@stencil/angular-output-target';

export const config: Config = {
  namespace: 'demo',
  outputTargets: [
    angularOutputTarget({
      componentCorePackage: 'component-library',
      directivesProxyFile: '../component-library-angular/src/directives/proxies.ts',
      valueAccessorConfigs: angularValueAccessorBindings,
    }),
    {
      type: 'dist',
    },
  ],
};

componentCorePackage

This is the NPM package name of your core stencil package. In the case of Ionic we chose ‘@ionic/core’. This is the package that gets published that contains just your web components. This package is then used by the Angular package as a dependency

proxiesFile

This is the output file that gets generated by the outputTarget. This file should be referencing a different package location. In the example case we are choosing a sibling directory’s src directory. We will then create an Angular package that exports all components defined in this file.

import { ComponentLibraryModule } from 'component-library-angular';

@NgModule({
  ...
  imports: [
    ComponentLibraryModule
  ],
  ...
})
export class AppModule { }