Angular Revisited: Tree-shakable Components and Optional NgModules

NgModule is arguably one of the most confusing Angular concepts. Using tree-shakable components and dependencies, we will need Angular modules less often or not at all. Tree-shakable components are not available yet, but we can use Single Component Angular Modules to ease the migration path.

Presented at:
- ngVikings conference, May 2019
- Angular In Depth conference, June 2019

Recording of talk from the ngVikings 2019 conference:
https://youtu.be/DA3efofhpq4

Article:
https://dev.to/this-is-angular/angular-revisited-tree-shakable-components-and-optional-ngmodules-36d2

Transcript

1. Angular Revisited
   Tree-shakable Components and Optional NgModules
   

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2. I think NgModule is something that if we didn’t have to,
   we wouldn’t introduce. Back in the day, there was a real
   need for it. With Ivy and other changes to Angular over
   the years, we are working towards making those
   optional.
   — Igor Minar at AngularConnect 2018
   

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3. The way NgModule works tends to be confusing to new
   Angular developers. Even if we weren’t to rip it out
   completely, we would change how it works and simplify
   things.
   — Alex Rickabaugh at AngularConnect 2018
   

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4. Ivy out-of-the-box
   • Faster builds
   • Better debugging
   • Smaller bundle size
   • Instruction set similar to Incremental DOM
   

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5. Ivy is well-suited for
   • Micro front-ends
   • Angular Elements
   • Web apps where Angular is not in control
   of the entire document
   

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6. Zoneless change detection with Ivy
   1. Change local UI state.
   2. Mark component for check.
   3. Schedule change detection
   cycle.
   @Component({
   selector: 'zippy',
   template: `{{title}}
   `,
   })
   export class ZippyComponent {
   @Input() title: string;
   isExpanded = false;
   onToggle() {
   this.isExpanded = !this.isExpanded;
   markDirty(this);
   }
   }
   ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
   

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7. We use Angular modules to
   • Configure injectors for runtime resolving of
   dependencies
   • Link declarables when compiling component
   templates
   • Bootstrap components as entry points to our
   applications
   • Lazy-load application features
   

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8. Tree-shakable components are
   • Entry components but tree-shakable by the
   build process
   • Self-contained and independent from Angular
   modules
   • The smallest compilation and code splitting
   unit for Angular
   

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9. import { Component, Input, ɵmarkDirty as markDirty } from '@angular/core';
   import { ButtonDirective } from './button.directive';
   @Component({
   deps: [
   ButtonDirective,
   ],
   selector: 'zippy',
   template: `{{title}}
   `,
   })
   export class ZippyComponent {
   @Input() title: string;
   isExpanded = false;
   onToggle() {
   this.isExpanded = !this.isExpanded;
   markDirty(this);
   }
   }
   Tree-shakable
   components with
   proposed component API
   ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
   

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10. import { Component } from '@angular/core';
    import { CapitalizePipe } from './capitalize.pipe';
    import { ZippyComponent } from './zippy.component';
    @Component({
    deps: [
    CapitalizePipe,
    ZippyComponent,
    ],
    template: `{{title | capitalize}}`,
    })
    export class AppComponent {
    title = 'proposed component API';
    }
    Tree-shakable
    components with
    proposed component API
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    

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11. Single component Angular modules
    • Declare and export only one component
    • Import only the declarables used by their specific
    component
    • Are useful for isolated component tests
    • Can be placed in the same file as their component
    • The abbreviated form is SCAM
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    

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12. import { Component, Input, NgModule } from '@angular/core';
    import { ButtonModule } from './button.directive';
    @Component({
    selector: 'zippy',
    template: `{{title}}
    `,
    })
    export class ZippyComponent {
    @Input() title: string;
    isExpanded = false;
    onToggle() {
    this.isExpanded = !this.isExpanded;
    }
    }
    @NgModule({
    declarations: [ZippyComponent],
    exports: [ZippyComponent],
    imports: [ButtonModule],
    })
    export class ZippyModule {}
    Faux tree-shakable
    components with
    SCAMs
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    

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13. import { Component, NgModule } from '@angular/core';
    import { CapitalizeModule } from './capitalize.pipe';
    import { ZippyModule } from './zippy.component';
    @Component({
    template: `{{title | capitalize}}`,
    })
    export class AppComponent {
    title = 'single component angular modules’;
    }
    @NgModule({
    declarations: [AppComponent],
    imports: [
    CapitalizeModule,
    ZippyModule,
    ],
    })
    export class AppModule {}
    Faux tree-shakable
    components with
    SCAMs
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    

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14. Component render modules
    • Exclusively declare dependencies, no Angular module
    imports
    • Declare all the declarables used by their specific
    component and additionally the component itself
    • Can have duplicate declarations between Angular
    modules
    • Only work because of a timing issue
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    

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15. import { Component, Input, NgModule, ɵmarkDirty as markDirty }
    from '@angular/core';
    import { ButtonDirective } from './button.directive';
    @Component({ selector: 'zippy',
    template: `{{title}}
    `,
    })
    export class ZippyComponent {
    @Input() title: string;
    isExpanded = false;
    onToggle() {
    this.isExpanded = !this.isExpanded;
    markDirty(this);
    }
    }
    @NgModule({ declarations: [
    ZippyComponent,
    ButtonDirective,
    ] })
    export class ZippyRenderModule {}
    Component render
    modules
    (Ivy preview with JIT)
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    

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16. import { Component, NgModule } from '@angular/core';
    import { CapitalizePipe } from './capitalize.pipe';
    import { ZippyComponent } from './zippy.component';
    @Component({
    template: `{{title | capitalize}}`,
    })
    export class AppComponent {
    title = 'component render modules’;
    }
    @NgModule({
    declarations: [
    AppComponent,
    CapitalizePipe,
    ZippyComponent,
    ],
    })
    export class AppRenderModule {}
    Component render
    modules
    (Ivy preview with JIT)
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    

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17. Feature render modules
    • Every component exports a nested declarable array
    • A single feature render module per bundle
    • Angular will flatten the declarable arrays and remove
    duplicates
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    

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18. import { Component, Input, ɵmarkDirty as markDirty } from '@angular/core';
    import { ButtonDirective } from './button.directive';
    @Component({
    selector: 'zippy',
    template: `{{title}}
    `,
    })
    export class ZippyComponent {
    @Input() title: string;
    isExpanded = false;
    onToggle() {
    this.isExpanded = !this.isExpanded;
    markDirty(this);
    }
    }
    export const zippyDeps = [
    ZippyComponent,
    ButtonDirective,
    ];
    Feature render
    modules
    (Ivy preview with AOT)
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    

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19. import { Component, NgModule } from '@angular/core';
    import { CapitalizePipe } from './capitalize.pipe';
    import { zippyDeps } from './zippy.component';
    @Component({
    template: `{{title | capitalize}}`,
    })
    export class AppComponent {
    title = 'feature render modules’;
    }
    @NgModule({
    declarations: [
    AppComponent,
    CapitalizePipe,
    zippyDeps,
    ],
    })
    export class AppRenderModule {}
    Feature render
    modules
    (Ivy preview with AOT)
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    

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20. We use Angular modules to
    • Configure injectors for runtime resolving of
    dependencies
    • Link declarables when compiling component
    templates
    • Bootstrap components as entry points to our
    applications
    • Lazy-load application features
    

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21. Bootstrapping tree-shakable components
    Unlike View Engine:
    • No NgZone
    • No default change detection
    • No application initialisers
    • No application initialisation
    status
    • No application bootstrap
    hook
    import { ɵrenderComponent as renderComponent }
    from '@angular/core';
    import { AppComponent } from './app.component';
    renderComponent(AppComponent);
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    

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22. We use Angular modules to
    • Configure injectors for runtime resolving of
    dependencies
    • Link declarables when compiling component
    templates
    • Bootstrap components as entry points to our
    applications
    • Lazy-load application features
    

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23. Lazy-loading tree-shakable components
    1. Dynamically import the
    component file
    2. Extract the component from
    the file
    3. Bootstrap the component
    import { ɵrenderComponent as renderComponent }
    from '@angular/core';
    import('./my-ivy.component').then(({ MyIvyComponent }) =>
    renderComponent(MyIvyComponent);
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    

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24. This talk is possible thanks to
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    Alexey Zuev Joost Koehoorn Max Koretskyi
    Morten Kirstein Wassim Chegham Zejiang Yu
    

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25. Tree-shakable components with Ivy
    • Get rid of all Angular modules
    • Bootstrap using renderComponent
    • Schedule change detection using markDirty when local
    UI state changes
    • Lazy-load application features using dynamic import
    and renderComponent
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    

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26. Techniques for getting started today
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    View Engine Ivy preview with JIT Ivy preview with AOT
    SCAMs ✓ ✓ ✓
    Component render modules ✓
    Feature render modules ✓ ✓
    Proposed component API
    

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27. Get in touch
    ANGULAR REVISITED: TREE-SHAKABLE COMPONENTS AND OPTIONAL NGMODULES
    bit.do/angular-revisited-slides
    bit.do/angular-revisited
    github.com/LayZeeDK/angular-revisited
    github.com/LayZeeDK
    twitter.com/LayZeeDK
    www.linkedin.com/in/larsgbn/
    larsbrinknielsen@gmail.com
    

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