bugfix(@nestjs/core) make use of default assignments when optional

Author: kamilmysliwiec

integration/injector/e2e/default-values.spec.ts

@@ -0,0 +1,16 @@
+import { Test } from '@nestjs/testing';
+import { expect } from 'chai';
+import { DefaultsModule } from '../src/defaults/defaults.module';
+import { DefaultsService } from '../src/defaults/defaults.service';
+
+describe('Injector', () => {
+  describe('when optional', () => {
+    it(`should make use of default assignments`, async () => {
+      const builder = Test.createTestingModule({
+        imports: [DefaultsModule],
+      });
+      const app = await builder.compile();
+      expect(app.get(DefaultsService).coreService.default).to.be.true;
+    });
+  });
+});

integration/injector/src/defaults/core.service.ts

@@ -0,0 +1,4 @@
+import { Injectable } from '@nestjs/common';
+
+@Injectable()
+export class CoreService {}

integration/injector/src/defaults/defaults.module.ts

@@ -0,0 +1,7 @@
+import { Module } from '@nestjs/common';
+import { DefaultsService } from './defaults.service';
+
+@Module({
+  providers: [DefaultsService],
+})
+export class DefaultsModule {}

integration/injector/src/defaults/defaults.service.ts

@@ -0,0 +1,11 @@
+import { Inject, Injectable, Optional } from '@nestjs/common';
+import { CoreService } from './core.service';
+
+@Injectable()
+export class DefaultsService {
+  constructor(
+    @Inject(CoreService)
+    @Optional()
+    public readonly coreService = { default: true },
+  ) {}
+}

packages/core/injector/injector.ts

@@ -187,7 +187,7 @@ export class Injector {
           if (!isOptional) {
             throw err;
           }
-          return null;
+          return undefined;
         }
       }),
     );