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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400, error_type='ValidationError'))
        if runtime.startswith('python') and not use_docker():
            try:
                
                ensure_readable(main_file)
                zip_file_content = load_file(main_file, mode='rb')
                
                lambda_handler = exec_lambda_code(
                    zip_file_content,
                    handler_function=handler_function,
                    lambda_cwd=lambda_cwd,
                    lambda_env=lambda_environment)
            except Exception as e:
                raise ClientError('Unable to get handler function from lambda code.', e)
    add_function_mapping(lambda_name, lambda_handler, lambda_cwd)
    return {'FunctionName': lambda_name}
def do_list_functions():
    funcs = []
    for f_arn, func in arn_to_lambda.items():
        if type(func) != LambdaFunction:
            continue
        func_name = f_arn.split(':function:')[-1]
        arn = func_arn(func_name)
        func_details = arn_to_lambda.get(arn)
        if not func_details:
            
            continue
        funcs.append(format_func_details(func_details))
    return funcs
def format_func_details(func_details, version=None, always_add_version=False):