mixed promise state when filtering using then()

[thomheymann]

The library is mixing up promise states when filtering return values:

var defer = $.Deferred(),
    filtered = defer.then( null, function( value ) {
        return value * 3;
    });

defer.reject( 6 );
filtered.fail(function( value ) {
    console.log( "Value is ( 3*6 = ) 18: " + value );
});
filtered.always(function( value ) {
    console.log( "State is: " + defer.state() );
    console.log( "Filtered State is: " + filtered.state() );
});

In browser using jQuery 1.8:

Value is ( 3*6 = ) 18: 18
State is: rejected
Filtered State is: rejected

In node using underscore.deferred:

State is: rejected
Filtered State is: resolved

I'm on 0.4.0 installed via npm

[wookiehangover]

This is expected behavior.

As specified, .then issues another promise, rather than holding the reference to the original promise that it's chaining from. This is a breaking change from the jQuery implementation, and is documented in the readme for 0.4.0. Take a look at @domenic's explanation of this part of the promises A spec for the detailed reasoning behind this change.

Apologies for the confusion!