feat(effects): allow non-dispatching effects to not return an action (#…

…1689)

modules/effects/spec/BUILD

@@ -12,6 +12,7 @@ ts_test_library(
         "//modules/effects",
         "//modules/store",
         "@npm//rxjs",
+        "@npm//ts-snippet",
     ],
 )
 

modules/effects/spec/effect_creator.spec.ts

@@ -0,0 +1,131 @@
+import { of } from 'rxjs';
+import { expecter } from 'ts-snippet';
+import { createEffect, getCreateEffectMetadata } from '../src/effect_creator';
+
+describe('createEffect()', () => {
+  describe('types', () => {
+    const expectSnippet = expecter(
+      code => `
+        import { Action } from '@ngrx/store';
+        import { createEffect } from '@ngrx/effects';
+        import { of } from 'rxjs';
+        ${code}`,
+      {
+        moduleResolution: 'node',
+        target: 'es2015',
+        baseUrl: '.',
+        experimentalDecorators: true,
+        paths: {
+          '@ngrx/store': ['./modules/store'],
+          '@ngrx/effects': ['./modules/effects'],
+          rxjs: ['../npm/node_modules/rxjs', './node_modules/rxjs'],
+        },
+      }
+    );
+
+    describe('dispatch: true', () => {
+      it('should enforce an Action return value', () => {
+        expectSnippet(`
+          const effect = createEffect(() => of({ type: 'a' }));
+        `).toSucceed();
+
+        expectSnippet(`
+          const effect = createEffect(() => of({ foo: 'a' }));
+        `).toFail(
+          /Type 'Observable<{ foo: string; }>' is not assignable to type 'Observable<Action> | ((...args: any[]) => Observable<Action>)'./
+        );
+      });
+
+      it('should enforce an Action return value when dispatch is provided', () => {
+        expectSnippet(`
+          const effect = createEffect(() => of({ type: 'a' }), { dispatch: true });
+        `).toSucceed();
+
+        expectSnippet(`
+          const effect = createEffect(() => of({ foo: 'a' }), { dispatch: true });
+        `).toFail(
+          /Type 'Observable<{ foo: string; }>' is not assignable to type 'Observable<Action> | ((...args: any[]) => Observable<Action>)'./
+        );
+      });
+    });
+
+    describe('dispatch: false', () => {
+      it('should enforce an Observable return value', () => {
+        expectSnippet(`
+          const effect = createEffect(() => of({ foo: 'a' }), { dispatch: false });
+        `).toSucceed();
+
+        expectSnippet(`
+          const effect = createEffect(() => ({ foo: 'a' }), { dispatch: false });
+        `).toFail(
+          /Type '{ foo: string; }' is not assignable to type 'Observable<Action> | ((...args: any[]) => Observable<Action>)'./
+        );
+      });
+    });
+  });
+
+  it('should flag the variable with a meta tag', () => {
+    const effect = createEffect(() => of({ type: 'a' }));
+
+    expect(effect.hasOwnProperty('__@ngrx/effects_create__')).toBe(true);
+  });
+
+  it('should dispatch by default', () => {
+    const effect: any = createEffect(() => of({ type: 'a' }));
+
+    expect(effect['__@ngrx/effects_create__']).toEqual({ dispatch: true });
+  });
+
+  it('should be possible to explicitly create a dispatching effect', () => {
+    const effect: any = createEffect(() => of({ type: 'a' }), {
+      dispatch: true,
+    });
+
+    expect(effect['__@ngrx/effects_create__']).toEqual({ dispatch: true });
+  });
+
+  it('should be possible to create a non-dispatching effect', () => {
+    const effect: any = createEffect(() => of({ type: 'a' }), {
+      dispatch: false,
+    });
+
+    expect(effect['__@ngrx/effects_create__']).toEqual({ dispatch: false });
+  });
+
+  it('should be possible to create a non-dispatching effect returning a non-action', () => {
+    const effect: any = createEffect(() => of('foo'), {
+      dispatch: false,
+    });
+
+    expect(effect['__@ngrx/effects_create__']).toEqual({ dispatch: false });
+  });
+
+  describe('getCreateEffectMetadata', () => {
+    it('should get the effects metadata for a class instance', () => {
+      class Fixture {
+        a = createEffect(() => of({ type: 'a' }));
+        b = createEffect(() => of({ type: 'b' }), { dispatch: true });
+        c = createEffect(() => of({ type: 'c' }), { dispatch: false });
+      }
+
+      const mock = new Fixture();
+
+      expect(getCreateEffectMetadata(mock)).toEqual([
+        { propertyName: 'a', dispatch: true },
+        { propertyName: 'b', dispatch: true },
+        { propertyName: 'c', dispatch: false },
+      ]);
+    });
+
+    it('should return an empty array if the effect has not been created with createEffect()', () => {
+      const fakeCreateEffect: any = () => {};
+      class Fixture {
+        a = fakeCreateEffect(() => of({ type: 'A' }));
+      }
+
+      const mock = new Fixture();
+
+      expect(getCreateEffectMetadata(mock)).toEqual([]);
+    });
+  });
+});

modules/effects/src/effect_creator.ts

@@ -4,26 +4,17 @@ import { EffectMetadata } from './models';
 
 const CREATE_EFFECT_METADATA_KEY = '__@ngrx/effects_create__';
 
-export function createEffect<T extends Action>(
-  source: (() => Observable<T>),
-  options: { dispatch: false }
-): Observable<T>;
-export function createEffect<T extends Action>(
-  source: (() => (...args: any[]) => Observable<T>),
-  options: { dispatch: false }
-): ((...args: any[]) => Observable<T>);
-export function createEffect<T extends Action>(
-  source: (() => Observable<T>),
-  options?: { dispatch: true }
-): Observable<T>;
-export function createEffect<T extends Action>(
-  source: (() => (...args: any[]) => Observable<T>),
-  options?: { dispatch: true }
-): ((...args: any[]) => Observable<T>);
-export function createEffect<T extends Action>(
-  source: (() => Observable<T>) | (() => (...args: any[]) => Observable<T>),
-  { dispatch = true } = {}
-): Observable<T> | ((...args: any[]) => Observable<T>) {
+export function createEffect<
+  R extends Observable<unknown> | ((...args: any[]) => Observable<unknown>)
+>(source: () => R, options: { dispatch: false }): R;
+export function createEffect<
+  T extends Action,
+  R extends Observable<T> | ((...args: any[]) => Observable<T>)
+>(source: () => R, options?: { dispatch: true }): R;
+export function createEffect<
+  T extends Action,
+  R extends Observable<T> | ((...args: any[]) => Observable<T>)
+>(source: () => R, { dispatch = true } = {}): R {
   const effect = source();
   Object.defineProperty(effect, CREATE_EFFECT_METADATA_KEY, {
     value: {

projects/example-app/src/app/books/effects/collection.effects.ts

@@ -18,11 +18,13 @@ export class CollectionEffects {
    *
    * The `defer` observable accepts an observable factory function
    * that is called when the observable is subscribed to.
-   * Wrapping the database open call in `defer` makes
+   * Wrapping the supported call in `defer` makes
    * effect easier to test.
    */
-  @Effect({ dispatch: false })
-  checkStorageSupport$ = defer(() => this.storageService.supported());
+  checkStorageSupport$ = createEffect(
+    () => defer(() => this.storageService.supported()),
+    { dispatch: false }
+  );
 
   loadCollection$ = createEffect(() =>
     this.actions$.pipe(