angularjs custom REST action and error handling - angularjs

Question

I'm having some trouble with error handling in a little angularjs application. I'm interacting with a Flask backend and a Postgres DB.
I have a factory service
appointServices.factory('Appointments', ['$resource', function($resource){
return $resource(someUrl, {}, {
query: { ... }
,
create: {
method: 'POST'
,url: 'http://somedomain:port/new/:name/:start/:end/:treatment'
,params: { start: '#start', end: '#end', name: '#name', treatment: '#treatment' }
,isArray:false
}
});
}
]);
Inside a controller I'm making the following call
Appointments.create($scope.appointment, function(value, responseHeaders) {
// success handler
console.debug('success: ', JSON.stringify(value));
}, function(httpResponse) {
// error handler
console.debug('error: ', JSON.stringify(httpResponse));
});
Here $scope.appointment contains the relevant parameters for the create action.
Now, in the backend I'm able to catch DB errors involving constraints and I'm trying to return an error code with a 'meaningful' message. So I have a python method
def create(name, start, end, treatment):
try:
...
transaction_status = 'ok'
code = 200
except IntegrityError as e:
...
transaction_status = 'IntegrityError'
code = 500
finally:
...
return make_response(transaction_status, code)
Everything works fine, I'm able to talk to the backend, create new data and insert this in the DB. As I said, any violation of the constraints is detected and the backend responds
curl -X POST "http://somedomain:port/new/foo/bar/baz/qux" -v
...
< HTTP/1.0 500 INTERNAL SERVER ERROR
...
IntegrityError
So, the problem is, no matter whether the action create was successful or not, the intended error handler specified inside the controller is always fired. Moreover, I always end up with a status code 404 in the httpResponse. Firebug shows correctly the code 500 as above, though.
Anybody has any idea of why I'm getting this behavior?
Any suggestions on how to improve the error handling mechanism are also welcome.
Thx in advance.
P.S. Following the documentation on $resource I have also tried variations on the factory service call, e.g.
Appointments.create({}, $scope.appointment, successCallback, errorCallback);
Appointments.create($scope.appointment, {}, successCallback, errorCallback);
with the same results.
Update:
Forgot to mention the important fact that I'm interacting with the backend via CORS requests. The POST request in create above is having place with the OPTIONS method instead. As I mentioned everything is working correctly except for the error response.
Under further investigation, I tried to isolate the factory service, in case I did something wrong, and I also tried the approach shown in the credit card example ($resource docs), but with no positive result.
However, I came up with two workarounds. Firstly, I was able to create a plain JQuery POST request, as in the example shown in the docs. This time, the request is not replaced by OPTIONS and I got the error code correctly.
I also managed to connect to the backend with the low-level $http service as follows:
var urlBase = 'http://somedomain:port/new/:name/:start/:end/:treatment';
var url = urlBase.replace(/:name/g, $scope.appointment.name);
url = url.replace(/:start/g, $scope.appointment.start);
url = url.replace(/:end/g, $scope.appointment.end);
url = url.replace(/:treatment/g, $scope.appointment.treatment);
// force method to be POST
var futureResponse = $http({ method: 'POST', url: url });
futureResponse.success(function (data, status, headers, config) {
console.debug('success: ', JSON.stringify(data));
});
futureResponse.error(function (data, status, headers, config) {
console.group('Error');
console.debug(JSON.stringify(status));
console.debug(JSON.stringify(data));
console.groupEnd();
});
This time, as in the case of JQuery, the request is done effectively with POST and error codes are correctly received.
Notice also that I'm not calling $http.post but I set the method to POST as part of the object parameter to $http, otherwise the connection takes places with OPTIONS as before.
Still trying to figure out what is happening with $resource.