Bug 269641 – checkValidity() of input[type="date"] returns an unexpected result when an entered value is replaced by an empty string.

• Status: NEW
• Component: Forms

Sample on JSFiddle: https://jsfiddle.net/xL581koz/

[Summary]
- After entering a value in input[type="date"], setting an empty string "" will cause checkValidity() to return false, despite the validityState values being correct. 
- So the form cannot be submit.
- No issues occur when using form reset to clear the value.

[Expected]
For the condition,
- checkValidity() returns true.
- The form can be submitted successfully.

[How to reproduce]
1. enter a valid value in the input[type="date"] of the form. 
2. set an empty string ("") to the input element in JS.

[Radar WebKit Bug Importer]

<rdar://problem/123549879>

[Anne van Kesteren]

I can also reproduce this for other form controls:

https://software.hixie.ch/utilities/js/live-dom-viewer/?%3Cinput%20type%3Dtime%3E%0A%3Cscript%3E%0Ainput%20%3D%20document.querySelector(%27input%27)%0Ainput.value%20%3D%20%2212%3A12%22%3B%0Ainput.value%20%3D%20%22%22%3B%0Aw(input.checkValidity())%0A%3C%2Fscript%3E

It seems that the problem is that as soon as a value is set some state gets initialized that is not reset when the value is "removed" again.

[Anne van Kesteren]

The problem appears to be that BaseDateAndTimeInputType::hasBadInput() starts returning true when input is set to the empty string after it's been non-empty and valid.