ngAttr added attributes don't trigger directives

[twhitbeck]

This may be by design, but I thought I'd bring it up.

Since ngAttr-prefixed attributes are interpolated with allOrNothing, an attribute may or may not be present initially. If the expression is defined on the first evaluation, it looks like the resulting attribute will trigger directives. However, if the expression is initially undefined, when it later becomes defined the attribute that is added will not cause any directives to be applied to the element.

My use case is this: I'm using ng-attr-min and ng-attr-max on an input[type=date] with something like ng-attr-min="{{minDate | date:'yyyy-MM-dd'}}". If minDate is undefined, I don't want there to be any min validation. When minDate becomes defined, the min attribute is properly set but the min directive is not applied retroactively, therefore I don't get my angular min validation.

The alternatives are

• Use ngMin, but this doesn't set the min attribute and on Chrome the datepicker won't be properly restricted.
• Use interpolation on min directly (e.g. min="{{minDate | date:'yyyy-MM-dd'}}"), but when minDate is undefined, this leaves a dangling min attribute with no value which incorrectly makes any value invalid (this might be a bug).

[caitp]

This is one of those difficult things --- unfortunately, we don't have a good way to trigger compilation when the DOM changes in this way. Attempting to do so would massively harm performance.

To add to this, there's also no way to "trigger" one particular directive, all you can do is compile an entire chunk of DOM. You could explicitly recompile the chunk of DOM you want to, but there isn't really a good way to do this.

[caitp]

oops, didn't mean to close that, maybe someone else will have something to say about it.

[pkozlowski-opensource]

Agree with @caitp that it would be very hard to support. I would suggest that we focus on the original issue of the conditional min validation here instead.

[gkalpak]

This is easy to work around by means of: min="{{(minDate || 0) | date:'yyyy-MM-dd'}}"
(It's not ideal though...)

[twhitbeck]

All makes sense.
It seems to me like the issue could be solved if the min directive could handle having a blank value by not validating.

<input type="date" min ng-model="date"> will invalidate any input.