fix(logger|metrics): return decorated class

packages/logger/src/Logger.ts

@@ -112,13 +112,13 @@ class Logger implements ClassThatLogs {
   }
 
   public injectLambdaContext(): HandlerMethodDecorator {
-    return (target, propertyKey, descriptor) => {
+    return (target, _propertyKey, descriptor) => {
       const originalMethod = descriptor.value;
 
       descriptor.value = (event, context, callback) => {
         this.addContext(context);
 
-        return originalMethod?.apply(this, [ event, context, callback ]);
+        return originalMethod?.apply(target, [ event, context, callback ]);
       };
     };
   }

packages/logger/tests/unit/Logger.test.ts

@@ -605,6 +605,45 @@ describe('Class: Logger', () => {
       jest.spyOn(console, 'log').mockImplementation(() => {});
     });
 
+    test('when used as decorator, it returns a function with the correct scope of the decorated class', async () => {
+
+      // Prepare
+      const logger = new Logger();
+      class LambdaFunction implements LambdaInterface {
+
+        @logger.injectLambdaContext()
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-ignore
+        public handler<TEvent, TResult>(_event: TEvent, _context: Context, _callback: Callback<TResult>): void | Promise<TResult> {
+          this.myClassMethod();
+        }
+
+        private myClassMethod (): void {
+          logger.info('This is an INFO log with some context');
+        }
+
+      }
+
+      // Act
+      await new LambdaFunction().handler(dummyEvent, dummyContext, () => console.log('Lambda invoked!'));
+
+      // Assess
+      expect(console['info']).toBeCalledTimes(1);
+      expect(console['info']).toHaveBeenNthCalledWith(1, JSON.stringify({
+        cold_start: true,
+        function_arn: 'arn:aws:lambda:eu-central-1:123456789012:function:foo-bar-function',
+        function_memory_size: 128,
+        function_name: 'foo-bar-function',
+        function_request_id: 'c6af9ac6-7b61-11e6-9a41-93e812345678',
+        level: 'INFO',
+        message: 'This is an INFO log with some context',
+        service: 'hello-world',
+        timestamp: '2016-06-20T12:08:10.000Z',
+        xray_trace_id: 'abcdef123456abcdef123456abcdef123456',
+      }));
+
+    });
+
     test('when used as decorator, it returns a function that captures Lambda\'s context information and adds it in the printed logs', async () => {
 
       // Prepare

packages/metrics/src/Metrics.ts

@@ -244,7 +244,7 @@ class Metrics implements MetricsInterface {
 
         let result: unknown;
         try {
-          result = await originalMethod?.apply(this, [ event, context, callback ]);
+          result = await originalMethod?.apply(target, [ event, context, callback ]);
         } catch (error) {
           throw error;
         } finally {

packages/metrics/tests/unit/Metrics.test.ts

@@ -535,12 +535,43 @@ describe('Class: Metrics', () => {
       expect(loggedData[1]._aws.CloudWatchMetrics[0].Metrics.length).toBe(0);
     });
 
+    test('Using decorator, it returns a function with the correct scope of the decorated class', async () => {
+
+      // Prepare
+      const metrics = new Metrics({ namespace: 'test' });
+      class LambdaFunction implements LambdaInterface {
+        @metrics.logMetrics({ defaultDimensions: { default: 'defaultValue' } })
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-ignore
+        public async handler<TEvent>(
+          _event: TEvent,
+          _context: Context): Promise<string> {
+          this.myMethod();
+
+          return 'Lambda invoked!';
+        }
+
+        private myMethod(): void {
+          metrics.addMetric('test_name', MetricUnits.Seconds, 10);
+        }
+      }
+
+      // Act
+      await new LambdaFunction().handler(dummyEvent, dummyContext.helloworldContext);
+
+      // Assess
+      expect(console.log).toBeCalledTimes(1);
+
+    });
+
     test('Using decorator on async handler (without callback) should work fine', async () => {
       const metrics = new Metrics({ namespace: 'test' });
       const additionalDimension = { name: 'metric2', value: 'metric2Value' };
 
       class LambdaFunction implements LambdaInterface {
         @metrics.logMetrics({ defaultDimensions: { default: 'defaultValue' } })
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-ignore
         public async handler<TEvent>(
           _event: TEvent,
           _context: Context): Promise<string> {