Detaching <select> with [multiple] attribute results in an exception

[ewenchou]

This looks similar to Issue #392 except affects select inputs with the multiple attribute specified.

Using the same HTML code from Issue #392 with multiple attribute:

<button ng-click="attached = !attached">Toggle!</button>
<div ng-if="attached">
  <select ng-model="irrelevant" multiple>
    <option>foo</option>
    <option>bar</option>
  </select>
  </div>
</div>

Click the Toggle button and then select one or more values. Then click the Toggle button again will produce this error:

The null object does not have a getter 'ngValue'.

NoSuchMethodError : method not found: 'ngValue'
Receiver: null
Arguments: []

With the stacktrace:

STACKTRACE:
#0      Object.noSuchMethod (dart:core-patch/object_patch.dart:45)
#1      _MultipleSelectionMode.onModelChange.<anonymous closure> (package:angular/directive/input_select.dart:225:70)
#2      _SelectMode._forEachOption (package:angular/directive/input_select.dart:139:24)
#3      _MultipleSelectionMode.onModelChange (package:angular/directive/input_select.dart:228:19)
#4      InputSelectDirective.dirty.<anonymous closure> (package:angular/directive/input_select.dart:73:28)
#5      relaxFnArgs.<anonymous closure> (package:angular/utils.dart:66:40)
#6      Scope.$eval (package:angular/core/scope.dart:616:43)
#7      Scope._digestHandleQueue (package:angular/core/scope.dart:481:20)
#8      Scope._digestWhileDirtyLoop (package:angular/core/scope.dart:439:44)
#9      Scope.$digest (package:angular/core/scope.dart:415:28)
#10     _autoDigestOnTurnDone (package:angular/core/scope.dart:108:14)
#11     _rootRun (dart:async/zone.dart:688)
#12     _ZoneDelegate.run (dart:async/zone.dart:417)
#13     NgZone._finishTurn (package:angular/core/zone.dart:97:21)
#14     NgZone._onRunBase (package:angular/core/zone.dart:57:20)
#15     _onRunUnary (package:angular/core/zone.dart:66:22)
#16     _ZoneDelegate.runUnary (dart:async/zone.dart:426)
#17     _CustomizedZone.runUnary (dart:async/zone.dart:631)
#18     _BaseZone.runUnaryGuarded (dart:async/zone.dart:546)
#19     _BaseZone.bindUnaryCallback.<anonymous closure> (dart:async/zone.dart:572)

I did a really rough patch on _MultipleSelectionMode.onModelChange in directive/input_select.dart (see below). Seems to work in my limited testing.

onModelChange(List selectedValues) {
  Function fn = (o, i) => o.selected = null;

  if (selectedValues is List) {
    // ORIGINAL CODE
    // fn = (o, i) => o.selected = selectedValues.contains(expando[o].ngValue);

    // MY CODE
    fn = (o, i) {
      if (expando[o] != null) {
       o.selected = selectedValues.contains(expando[o].ngValue);
      } else {
        o.selected = false;
      }
    };
  }