fix(tracer): capture method throws errors correctly (#1016)

* wip

* wip

* fix: captureMethod now throws

* chore: removed leftover comment

Author: dreamorosi

Diff for: packages/tracer/src/Tracer.ts

@@ -421,17 +421,18 @@ class Tracer extends Utility implements TracerInterface {
           return originalMethod.apply(target, [...args]);
         }
 
-        return this.provider.captureAsyncFunc(`### ${originalMethod.name}`, async subsegment => {
+        return this.provider.captureAsyncFunc(`### ${originalMethod.name}`, async subsegment => {          
           let result;
           try {
             result = await originalMethod.apply(this, [...args]);
             this.addResponseAsMetadata(result, originalMethod.name);
           } catch (error) {
-            this.addErrorAsMetadata(error as Error);
-            // TODO: should this error be thrown?? If thrown we get a ERR_UNHANDLED_REJECTION. If not aren't we are basically catching a Customer error?
-            // throw error;
+            this.addErrorAsMetadata(error as Error); 
+            
+            throw error;
           } finally {
             subsegment?.close();
+            subsegment?.flush();
           }
 
           return result;

Diff for: packages/tracer/tests/unit/Tracer.test.ts

@@ -17,10 +17,10 @@ interface LambdaInterface {
 type CaptureAsyncFuncMock = jest.SpyInstance<unknown, [name: string, fcn: (subsegment?: Subsegment) => unknown, parent?: Segment | Subsegment]>;
 const createCaptureAsyncFuncMock = function(provider: ProviderServiceInterface): CaptureAsyncFuncMock {
   return jest.spyOn(provider, 'captureAsyncFunc')
-    .mockImplementation((methodName, callBackFn) => {
+    .mockImplementation(async (methodName, callBackFn) => {
       const subsegment = new Subsegment(`### ${methodName}`);
       jest.spyOn(subsegment, 'flush').mockImplementation(() => null);
-      callBackFn(subsegment);
+      await callBackFn(subsegment);
     });
 };
 
@@ -865,7 +865,6 @@ describe('Class: Tracer', () => {
       const captureAsyncFuncSpy = jest.spyOn(tracer.provider, 'captureAsyncFunc');
       class Lambda implements LambdaInterface {
 
-        // TODO: revisit return type & make it more specific
         @tracer.captureMethod()
         // eslint-disable-next-line @typescript-eslint/ban-ts-comment
         // @ts-ignore
@@ -895,6 +894,7 @@ describe('Class: Tracer', () => {
       // Prepare
       const tracer: Tracer = new Tracer();
       const newSubsegment: Segment | Subsegment | undefined = new Subsegment('### dummyMethod');
+      jest.spyOn(newSubsegment, 'flush').mockImplementation(() => null);
       jest.spyOn(tracer.provider, 'getSegment')
         .mockImplementation(() => newSubsegment);
       setContextMissingStrategy(() => null);
@@ -960,17 +960,16 @@ describe('Class: Tracer', () => {
 
       }
 
-      // Act
-      await new Lambda().handler(event, context, () => console.log('Lambda invoked!'));
-
-      // Assess
+      // Act / Assess
+      await expect(new Lambda().handler({}, context, () => console.log('Lambda invoked!'))).rejects.toThrowError(Error);
       expect(captureAsyncFuncSpy).toHaveBeenCalledTimes(1);
       expect(newSubsegment).toEqual(expect.objectContaining({
         name: '### dummyMethod',
       }));
       expect('cause' in newSubsegment).toBe(true);
       expect(addErrorSpy).toHaveBeenCalledTimes(1);
       expect(addErrorSpy).toHaveBeenCalledWith(new Error('Exception thrown!'), false);
+      expect.assertions(6);
 
     });