fix(core): correct misunderstanding of optional metadata

integration/injector/e2e/inherited-optional-dependency.ts

@@ -0,0 +1,64 @@
+import { Injectable, mixin, Module, Optional } from '@nestjs/common';
+import { Test } from '@nestjs/testing';
+
+import * as chai from 'chai';
+import * as chaiAsPromised from 'chai-as-promised';
+import { expect } from 'chai';
+import { UnknownDependenciesException } from '@nestjs/core/errors/exceptions/unknown-dependencies.exception';
+
+chai.use(chaiAsPromised);
+
+describe('Inherited optional dependency', () => {
+  const Foo = () => {
+    class FooMixin {
+      constructor(@Optional() option: any) {}
+    }
+    return mixin(FooMixin);
+  };
+
+  @Injectable()
+  class NeededService {
+    exec() {
+      return 'exec';
+    }
+  }
+
+  @Module({
+    providers: [NeededService],
+    exports: [NeededService],
+  })
+  class SomeModule {}
+
+  @Injectable()
+  class FooService extends Foo() {
+    constructor(private readonly neededService: NeededService) {
+      super();
+    }
+
+    doSomething() {
+      return this.neededService.exec();
+    }
+  }
+
+  @Module({
+    imports: [],
+    providers: [FooService],
+    exports: [FooService],
+  })
+  class FooModule {}
+
+  /**
+   * You can see details on this issue here: https://github.com/nestjs/nest/issues/2581
+   */
+  it('should remove optional dependency metadata inherited from base class', async () => {
+    const module = Test.createTestingModule({
+      imports: [SomeModule, FooModule],
+    });
+
+    await expect(
+      module.compile(),
+    ).to.eventually.be.rejected.and.be.an.instanceOf(
+      UnknownDependenciesException,
+    );
+  });
+});

packages/core/injector/injector.ts

@@ -395,7 +395,7 @@ export class Injector {
   }
 
   public reflectOptionalParams<T>(type: Type<T>): any[] {
-    return Reflect.getMetadata(OPTIONAL_DEPS_METADATA, type) || [];
+    return Reflect.getOwnMetadata(OPTIONAL_DEPS_METADATA, type) || [];
   }
 
   public reflectSelfParams<T>(type: Type<T>): any[] {