The update_function_configuration currently returns an empty dict no matter what but certain lambda libraries (ie, Zappa) require a realistic return value... which is simply the current config after being updated.

https://github.com/localstack/localstack/blob/9cba1010dfcbf2b7672df4d7da46b7e8ab287f64/localstack/services/awslambda/lambda_api.py#L872

https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/lambda.html#Lambda.Client.update_function_configuration

There might also be some other magic enriching that result but my quick read-through looks like it's an empty dict.



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testutil.create_lambda_function(
            func_name=TEST_LAMBDA_NAME_JAVA_STREAM,
            zip_file=cls.test_java_jar,
            runtime=LAMBDA_RUNTIME_JAVA8,
            handler='cloud.localstack.sample.LambdaStreamHandler'
        )
        
        testutil.create_lambda_function(
            func_name=TEST_LAMBDA_NAME_JAVA_SERIALIZABLE,
            zip_file=cls.test_java_zip,
            runtime=LAMBDA_RUNTIME_JAVA8,
            handler='cloud.localstack.sample.SerializedInputLambdaHandler'
        )
    @classmethod
    def tearDownClass(cls):
        
        testutil.delete_lambda_function(TEST_LAMBDA_NAME_JAVA)
        testutil.delete_lambda_function(TEST_LAMBDA_NAME_JAVA_STREAM)
        testutil.delete_lambda_function(TEST_LAMBDA_NAME_JAVA_SERIALIZABLE)
    def test_java_runtime(self):
        self.assertIsNotNone(self.test_java_jar)
        result = self.lambda_client.invoke(
            FunctionName=TEST_LAMBDA_NAME_JAVA, Payload=b'{}')
        result_data = result['Payload'].read()
        self.assertEqual(result['StatusCode'], 200)
        self.assertIn('LinkedHashMap', to_str(result_data))
    def test_sns_event(self):
        result = self.lambda_client.invoke(
            FunctionName=TEST_LAMBDA_NAME_JAVA, InvocationType='Event',
            Payload=b'{"Records": [{"Sns": {"Message": "{}"}}]}')