In every $http call with .then(successFunc) and .catch(errFunc) (alternatively then(successFunc, errFunc) the then/success is always called (the promise is successfully resolved).
Example
$http.get('/some/resource')
// /some/resource --> HTTP 400
.then(function(response)
{
console.log('success');
})
.catch(function(reason)
{
console.log('error');
})
// Console:
// - success
Is this the intended behaviour or what causes this?
No, this is not intended behaviour. Normally it should call .then() on HTTP 2xx and .catch() on HTTP 4xx and HTTP 5xx (not sure about the others).
The described behaviour is probably caused by another .catch() returning a resolved promise.
In a slightly changed example:
//In some Service:
function getResources()
{
$http.get('/some/resource')
// /some/resource --> HTTP 400
.then(function(response)
{
console.log('service success');
return response;
})
.catch(function(reason)
{
console.log('service error');
// IMPORTANT: although this is returned
// in a .catch() it returns a resolved promise
return reason;
});
}
//In some Controller:
someService.getResources()
.then(function(response)
{
console.log('controller success');
})
.catch(function(reason)
{
console.log('controller error');
});
// Console:
// - service error
// - controller success
Note that this can also be caused by a registered http interceptor:
$httpProvider.interceptors.push(function($q)
{
return {
'response': function(response)
{
// do something
return response;
},
'responseError': function(rejection)
{
// do something
return rejection; // <-- this causes the problem
// instead do
return $q.reject(rejection);
}
}
}
Your example converts a rejection to a resolved promise.
$http.get('/some/resource')
// /some/resource --> HTTP 400
.then(function(response)
{
console.log('success');
//IMPORTANT -- return to chain data
return response;
})
.catch(function(reason)
{
console.log('error');
//IMPORTANT -- throw to chain rejections
throw reason;
})
When a catch handler omits a throw statement, the function returns undefined which converts the rejection to a promise that resolves undefined.
Look in your code for a http interceptor that is following the same erroneous pattern.
The rule in functional programming is always return (or throw) something.
throw keyword in use with promises. Do you have any example demonstrating the correct behaviour?
return $q.reject(reason) over throw reason (see Angular $http docs).