fix(v8/aws-lambda): Avoid overwriting root span name (#15054)

backport of #15000

Author: Lms24

packages/aws-serverless/src/sdk.ts

@@ -220,10 +220,7 @@ function enhanceScopeWithEnvironmentData(scope: Scope, context: Context, startTi
  * @param context AWS Lambda context that will be used to extract some part of the data
  */
 function enhanceScopeWithTransactionData(scope: Scope, context: Context): void {
-  scope.addEventProcessor(event => {
-    event.transaction = context.functionName;
-    return event;
-  });
+  scope.setTransactionName(context.functionName);
   scope.setTag('server_name', process.env._AWS_XRAY_DAEMON_ADDRESS || process.env.SENTRY_NAME || hostname());
   scope.setTag('url', `awslambda:///${context.functionName}`);
 }

packages/aws-serverless/test/sdk.test.ts

@@ -18,6 +18,7 @@ const mockScope = {
   setTag: jest.fn(),
   setContext: jest.fn(),
   addEventProcessor: jest.fn(),
+  setTransactionName: jest.fn(),
 };
 
 jest.mock('@sentry/node', () => {
@@ -81,12 +82,8 @@ const fakeCallback: Callback = (err, result) => {
 };
 
 function expectScopeSettings() {
-  expect(mockScope.addEventProcessor).toBeCalledTimes(1);
-  // Test than an event processor to add `transaction` is registered for the scope
-  const eventProcessor = mockScope.addEventProcessor.mock.calls[0][0];
-  const event: Event = {};
-  eventProcessor(event);
-  expect(event).toEqual({ transaction: 'functionName' });
+  expect(mockScope.setTransactionName).toBeCalledTimes(1);
+  expect(mockScope.setTransactionName).toBeCalledWith('functionName');
 
   expect(mockScope.setTag).toBeCalledWith('server_name', expect.anything());
 

packages/core/src/scope.ts

@@ -306,7 +306,15 @@ class ScopeClass implements ScopeInterface {
   }
 
   /**
-   * @inheritDoc
+   * Sets the transaction name on the scope so that the name of e.g. taken server route or
+   * the page location is attached to future events.
+   *
+   * IMPORTANT: Calling this function does NOT change the name of the currently active
+   * root span. If you want to change the name of the active root span, use
+   * `Sentry.updateSpanName(rootSpan, 'new name')` instead.
+   *
+   * By default, the SDK updates the scope's transaction name automatically on sensible
+   * occasions, such as a page navigation or when handling a new request on the server.
    */
   public setTransactionName(name?: string): this {
     this._transactionName = name;