Incorrect expression results with && and array and object access

[royaldark]

This issue affects Angular 1.4.0. The 1.3.x branch appears unaffected.

Expressions which contain a && clause with a true thing on the left, and a null/undefined thing on the right which uses the form obj[index].key, return the true thing even though the second half of the && was falsy. See examples:

Expression: a[0].asdf && 72 (where a is undefined)
Expected: undefined
Actual: undefined

Expression: 72 && a[0].asdf (where a is undefined)
Expected: undefined
Actual: 72

This can even be reproduced with object literals:
Expression: 72 && ({})[0].asdf
Expected: undefined
Actual: 72

By inspecting the function returned by $parse(expression) it is fairly easy to see the faulty logic:

> $parse('72 && ({})[0].asdf').toString()
function (s,l,a,i){var v0,v1,v2,v3;v0=72;if(v0){v2={};if(v2!=null){v3=0;ensureSafeMemberName(v3,text);v1=ensureSafeObject(v2[v3],text);if(v1!=null){v0=v1.asdf;}}}return v0;}

Prettified:

function (s,l,a,i){
  var v0, v1, v2, v3;

  v0 = 72;

  if (v0) {
    v2 = {};

    if (v2 != null) {
      v3 = 0;
      ensureSafeMemberName(v3, text);
      v1 = ensureSafeObject(v2[v3], text);

      if (v1 != null) {
        v0 = v1.asdf;
      }
    }
  }

  return v0;
}

Tracing the execution and filling out the variables gives the following values:

v0 = 72
v1 = v2[v3] == {}[0] == undefined
v2 = {}
v3 = 0

Now notice the last nested if. Since v1 == undefined and !(undefined != null), that if is skipped and execution skips to the final line, where v0 = 72 is returned, despite v1 (the right-hand side of the &&) being undefined.

[gkalpak]

This should have been fixed on master (by #11989).
@royaldark, could you please verify that it is indeed fixed when using the latest build and close this issue if it works as expected ?

[lgalfaso]

This was fixed by #11989 and should make it into 1.4.1