When st-sort is used with ng-attr- and the expression for ng-attr-st-sort yields undefined, (i.e. ng-attr-st-sort='{{(someConditionToToggleSortability && 'true') || undefined}}', where someConditionToToggleSortability is false) the directive will be executed despite the st-sort attribute not actually being present in the DOM and the predicate variable will be undefined.
Additionally, newValue will simply have no predicate property at all. As a result, the condition was reducing to undefined !== undefined, which is, of course, false. This then causes the sorted-ascending arrow to appear on every column despite the fact that the items are still ordered naturally as, due to the absent predicate, sort() is never actually called.
Incidentally, if you do this but also provide st-sort-default='reverse', the sorted-descending arrow appears, as you might expect.
This change simply tightens the condition such that the table will not visually report that it has been sorted if there is no sort predicate.
This appears to be related to AngularJS Issue 14575, and the AngularJS team has declined to alter this behavior. Evidently ng-attr will always add the attribute first, but during normalization it is removed, causing the behavior I've described. You can see where the removal occurs on line 1756 in Angular's compile.js. The call to this function is on line 3352 of the same file. This behavior seems to have been present since the compiler refactor in 1.0.0rc1 so I think trying to anticipate users that might attempt this sort of dynamic directive behavior might be prudent.
When
st-sortis used withng-attr-and the expression forng-attr-st-sortyieldsundefined, (i.e.ng-attr-st-sort='{{(someConditionToToggleSortability && 'true') || undefined}}', wheresomeConditionToToggleSortabilityisfalse) the directive will be executed despite thest-sortattribute not actually being present in the DOM and thepredicatevariable will beundefined.Additionally,
newValuewill simply have nopredicateproperty at all. As a result, the condition was reducing toundefined !== undefined, which is, of course,false. This then causes the sorted-ascending arrow to appear on every column despite the fact that the items are still ordered naturally as, due to the absentpredicate,sort()is never actually called.Incidentally, if you do this but also provide
st-sort-default='reverse', the sorted-descending arrow appears, as you might expect.This change simply tightens the condition such that the table will not visually report that it has been sorted if there is no sort predicate.
This appears to be related to AngularJS Issue 14575, and the AngularJS team has declined to alter this behavior. Evidently
ng-attrwill always add the attribute first, but during normalization it is removed, causing the behavior I've described. You can see where the removal occurs on line 1756 in Angular's compile.js. The call to this function is on line 3352 of the same file. This behavior seems to have been present since the compiler refactor in 1.0.0rc1 so I think trying to anticipate users that might attempt this sort of dynamic directive behavior might be prudent.