[Bug Report] VFileInput multiple="false" changes the value for rules

[Aukemid]

Environment

Vuetify Version: 2.1.7
Vue Version: 2.6.10
Browsers: Chrome 78.0.3904.70
OS: Mac OS 10.15.1

Steps to reproduce

See codepen in the reproduction link.

1. Add a file in the first file input and the value parameter in the rules function is a File object. See console.
2. Add a file in the second file input and the File object is wrapped in an array. This should be the same as in step 1.

Expected Behavior

The value parameter of the rules functions should be a File object if you don't set the multiple property or set multiple to false.

Actual Behavior

If you don't set the multiple property, the value in the rules function is a File object as it should be. If you set multiple to false the value is an array which contains the File object.

Reproduction Link

https://codepen.io/Aukemid/pen/BaawqEM

Other comments

I believe this is caused by VFileInput.isMultiple which only checks whether the multiple property exists. The following change works in my test cases.

isMultiple() {
  // return this.$attrs.hasOwnProperty('multiple');
  return this.$attrs.hasOwnProperty('multiple') && this.$attrs.multiple !== false;
},

[all43]

Still relevant for 2.3.16.
If we have <v-file input :multiple="false" /> it won't allow you select multiple files (as $attrs passed directly to the input), but still wraps value in array, as property only checked for existence not truthiness.