How to handle errors via Ferry GraphQL - flutter

Question

community!
Please give a clue how to handle GraphQL errors by Ferry.
To simplify let's say that I have toLogin function:
await toLogin(_email, _password);
and it initiates login procedure:
Future<void> sendLogin(String _email, String _password) async {
final _sendLoginRequest = GLoginReq((b) => b
..vars.identifier = _email
..vars.password = _password);
final _client = initClient();
final _storage = GetStorage();
_client.request(_sendLoginRequest).listen((response) {
if (response.hasErrors) {
print('error');
} else {
print('success');
}
});
}
Works fine but I need to add error handling at the main program.
so I add
String _result = await toLogin(_email, _password);
to the main and return to the toLogin();
Future<String> sendLogin(String _email, String _password) async {
final _sendLoginRequest = GLoginReq((b) => b
..vars.identifier = _email
..vars.password = _password);
final _client = initClient();
String _result = 'init';
_client.request(_sendLoginRequest).listen((response) {
if (response.hasErrors) {
print('error');
_result = 'error';
} else {
print('success');
_result = 'success';
}
});
return _result;
}
The problem is that it returns _result before any check and Dart do not allow me to use await
OK, let's try another way:
var _response = OperationResponse(
operationRequest: _sendLoginRequest,
);
var _checkErrors = _response.graphqlErrors;
print(_checkErrors);
But it's always false
I've found option graphqlErrors at OperationResponse but do not have any idea what to fill there.
Please give me a clue how to handle it.
I use Strapi as the backend, the error example is as follows:
{
"errors": [
{
"message": "Bad Request",
"locations": [
{
"line": 2,
"column": 3
}
],
"path": [
"login"
],
"extensions": {
"code": "INTERNAL_SERVER_ERROR",
"exception": {
"code": 400,
"data": {
"statusCode": 400,
"error": "Bad Request",
"message": [
{
"messages": [
{
"id": "Auth.form.error.invalid",
"message": "Identifier or password invalid."
}
]
}
],
"data": [
{
"messages": [
{
"id": "Auth.form.error.invalid",
"message": "Identifier or password invalid."
}
]
}
]
},
"stacktrace": [
"Error: Bad Request",
" at checkBadRequest (C:\\Projects\\Zhugory\\zhugory-strapi-graphql\\zhugory-strapi\\node_modules\\strapi-plugin-users-permissions\\config\\schema.graphql.js:13:23)",
" at resolver (C:\\Projects\\Zhugory\\zhugory-strapi-graphql\\zhugory-strapi\\node_modules\\strapi-plugin-users-permissions\\config\\schema.graphql.js:217:11)",
" at runMicrotasks (<anonymous>)",
" at processTicksAndRejections (internal/process/task_queues.js:93:5)"
]
}
}
}
],
"data": null
}