Observed TypeError - Illegal invocation exception when deep watching an object containing FileList object.

[vinayk406]

Browser : chrome
Angular Version : 1.4.8

Plnkr: https://plnkr.co/edit/EjTuiuG9LXaEm2KUnThn?p=preview

Exception in firefox: 'name' getter called on an object that does not implement interface File.

[gkalpak]

This happens because you are using deep equality. As mentioned in the docs, using objectEquality: true will copy the object (so it can compare it with subsequent values and detect changes) using angular.copy() (and watching complex objects can have adverse implications).

File objects can't be properly copied, thus the error. You could use "normal" (non-deep) watch on the file-list itself or shallow watch details using $watchCollection(): Updated plnkr

[vinayk406]

As the watch expression in my case is dynamic, neither can use $watchCollection nor normal watch.
Why can't the framework ignore the copying of Special Objects(FileList in this case) in the deep watch scenario and compare only on the references?

[gkalpak]

Closing as duplicate of #14352 (well, it's the other way around, but #14352 has more participants 😃).
Let's track the issue there.