select option with ngValue="undefined" doesn't put undefined on ngModel

[Jorge-Martins]

I'm submitting a ...

• bug report
• feature request
• other

Current behavior:

When adding options with ngRepeat, if one of the options has ngValue="undefined" and ngModel is currently undefined, AngularJS still adds the unknown model option with value "? undefined:undefined ?" instead of the element with value "undefined:undefined" being selected. Moreover, if we select the element with value "undefined:undefined" the model is set to null instead of being undefined. For all the remaining values the behavior is as expected.

Expected / new behavior:

We expected that the option with value "? undefined:undefined ?" would not be added by AngularJS and that the selected option would be the one with ngValue="undefined". Also, we expected the ngModel to be set to undefined when that same option with ngValue="undefined" is selected.

Minimal reproduction of the problem with instructions:

https://plnkr.co/edit/5jIspWCuuMFl5CEhHexD?p=preview

AngularJS version: 1.6.x, 1.7.x

Browser: [all | Chrome XX | Firefox XX | Edge XX | IE XX | Safari XX | Mobile Chrome XX | Android X.X Web Browser | iOS XX Safari | iOS XX UIWebView | iOS XX WKWebView ]

all
Anything else: