feat: memoize function by arg

help-me-mom · Feb 3, 2018 · cac00b3 · cac00b3
1 parent 78fc8e3
commit cac00b3
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Showing 3 changed files with 28 additions and 14 deletions.
diff --git a/README.md b/README.md
@@ -25,14 +25,11 @@ import { TestedComponent } from './tested.component';
 
 describe('TestedComponent', () => {
   let fixture: ComponentFixture<TestedComponent>;
-  const mockedDependencyComponent = MockComponent(DependencyComponent); // do this if you want to select By.directive
 
   beforeEach(async() => {
     TestBed.configureTestingModule({
       declarations: [
-        mockedDependencyComponent, // to add your already mocked component if you went the by directive route
-        // or
-        MockComponent(DependencyComponent) // you can do this if you don't mind selecting by css selector
+        MockComponent(DependencyComponent)
       ]
     })
     .compileComponents();
@@ -53,7 +50,7 @@ describe('TestedComponent', () => {
 
   it('should do something when the dependency component emits on its output', () => {
     const mockedComponent = fixture.debugElement
-                                   .query(By.directive(mockedDependencyComponent))
+                                   .query(By.directive(MockComponent(DependencyComponent)))
                                    .componentInstance as DependencyComponent; // casting to retain type safety
     // again, let's pretend DependencyComponent has an output called 'someOutput'
     // emit on the output that MockComponent setup when generating the mock of Dependency Component

diff --git a/lib/mock_component.spec.ts b/lib/mock_component.spec.ts
@@ -30,8 +30,6 @@ export class ExampleComponentContainer {
 describe('MockComponent', () => {
   let component: ExampleComponentContainer;
   let fixture: ComponentFixture<ExampleComponentContainer>;
-  const mockedSimpleComponent = MockComponent(SimpleComponent);
-  const mockedEmptyComponent = MockComponent(EmptyComponent);
 
   getTestBed().initTestEnvironment(
     BrowserDynamicTestingModule,
@@ -42,8 +40,8 @@ describe('MockComponent', () => {
     TestBed.configureTestingModule({
       declarations: [
         ExampleComponentContainer,
-        mockedEmptyComponent,
-        mockedSimpleComponent
+        MockComponent(EmptyComponent),
+        MockComponent(SimpleComponent)
       ],
       imports: [
         FormsModule
@@ -65,7 +63,7 @@ describe('MockComponent', () => {
   it('should have the input set on the mock component', () => {
     fixture.detectChanges();
     const mockedComponent = fixture.debugElement
-                                   .query(By.directive(mockedSimpleComponent))
+                                   .query(By.directive(MockComponent(SimpleComponent)))
                                    .componentInstance as SimpleComponent;
     expect(mockedComponent.someInput).toEqual('hi');
     expect(mockedComponent.someInput2).toEqual('bye');
@@ -74,7 +72,7 @@ describe('MockComponent', () => {
   it('should trigger output bound behavior', () => {
     fixture.detectChanges();
     const mockedComponent = fixture.debugElement
-                                   .query(By.directive(mockedSimpleComponent))
+                                   .query(By.directive(MockComponent(SimpleComponent)))
                                    .componentInstance as SimpleComponent;
     mockedComponent.someOutput1.emit('hi');
     expect(component.emitted).toEqual('hi');
@@ -87,19 +85,27 @@ describe('MockComponent', () => {
   });
 
   it('should give each instance of a mocked component its own event emitter', () => {
-    const mockedComponents = fixture.debugElement.queryAll(By.directive(mockedSimpleComponent));
+    const mockedComponents = fixture.debugElement
+                                    .queryAll(By.directive(MockComponent(SimpleComponent)));
     const mockedComponent1 = mockedComponents[0].componentInstance as SimpleComponent;
     const mockedComponent2 = mockedComponents[1].componentInstance as SimpleComponent;
     expect(mockedComponent1.someOutput1).not.toEqual(mockedComponent2.someOutput1);
   });
 
   it('should work with components w/o inputs or outputs', () => {
-    const mockedComponent = fixture.debugElement.query(By.directive(mockedEmptyComponent));
+    const mockedComponent = fixture.debugElement
+                                   .query(By.directive(MockComponent(EmptyComponent)));
     expect(mockedComponent).not.toBeNull();
   });
 
   it('should allow ngModel bindings', () => {
     const mockedComponent = fixture.debugElement.query(By.css('#ngmodel-component'));
     expect(mockedComponent).not.toBeNull();
   });
+
+  it('should memoize the return value by argument', () => {
+    expect(MockComponent(EmptyComponent)).toBe(MockComponent(EmptyComponent));
+    expect(MockComponent(SimpleComponent)).toBe(MockComponent(SimpleComponent));
+    expect(MockComponent(EmptyComponent)).not.toBe(MockComponent(SimpleComponent));
+  });
 });
diff --git a/lib/mock_component.ts b/lib/mock_component.ts
@@ -1,7 +1,14 @@
 import { Component, EventEmitter, forwardRef, Type } from '@angular/core';
 import { ControlValueAccessor, NG_VALUE_ACCESSOR } from '@angular/forms';
 
+const cache = new Map<Type<Component>, Type<Component>>();
+
 export function MockComponent<TComponent>(component: Type<TComponent>): Type<TComponent> {
+  const cacheHit = cache.get(component);
+  if (cacheHit) {
+    return cacheHit as Type<TComponent>;
+  }
+
   const annotations = (component as any).__annotations__[0] || {};
   const propertyMetadata = (component as any).__prop__metadata__ || {};
 
@@ -37,8 +44,12 @@ export function MockComponent<TComponent>(component: Type<TComponent>): Type<TCo
   }
 
   /* tslint:disable:no-angle-bracket-type-assertion */
-  return Component(options)(<any> ComponentMock as Type<TComponent>);
+  const mockedComponent = Component(options)(<any> ComponentMock as Type<TComponent>);
   /* tslint:enable:no-angle-bracket-type-assertion */
+
+  cache.set(component, mockedComponent);
+
+  return mockedComponent;
 }
 
 function isInput(propertyMetadata: any): boolean {