1749427 - Decreasing value of input type time and max defined with JavaScript stepDown does not yield the expected value

Status: NEW

(Core :: DOM: Forms, defect)

Description

[Jacques Deguest]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:95.0) Gecko/20100101 Firefox/95.0

Steps to reproduce:

Consider the following html:

<input type="time" min="17:00" step="900" />

and call stepUp, it will set the value the first time to 17:00, then the second time to 17:15, etc. However, the other way around is not true, i.e.

 <input type="time" max="17:00" step="900" />

Then a call to stepDown will not yield the value 17:00, but instead 23:45, the second call will set the value to 17:00 and the third call will set the value to 16:45.

Actual results:

let input1 = document.createElement('input');
input1.setAttribute('type', 'time');
input1.setAttribute('min', '17:00');
input1.setAttribute('step', 900);
input1.value; // ""
input1.stepUp();
input1.value; // "17:00"
// However
let input2 = document.createElement('input');
input2.setAttribute('type', 'time');
input2.setAttribute('max', '17:00');
input2.setAttribute('step', 900);
input2.value; // ""
input2.stepDown();
input2.value; // "23:45"
input2.stepDown();
input2.value; // "17:00"
input2.stepDown();
input2.value; // "16:45"

Expected results:

I think calling stepDown on an input with a max HTML attribute defined should do like calling stepUp on an input with min HTML attribute defined, i.e. set the value to the baseline (min or max).

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Layout: Form Controls' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:emilio, could you have a look please?

For more information, please visit auto_nag documentation.

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:peterv, could you have a look please?

For more information, please visit auto_nag documentation.

Comment 4

[Vincent Hilla [:vhilla]]

Attachment: test_bug1749427.html

Comment 5

[Vincent Hilla [:vhilla]]

For <input type=time max=17:00 step=900> and stepDown, Blink sets the value to 0:00 while we compute 23:45. The spec is slightly ambiguous here.

What is happening is that in Gecko GetValueIfStepped / spec stepDown, value is empty and thus taken as zero. We subtract 15 minutes, value becomes negative and thus less than the maximum (see step 9). In step 11 / ConvertNumberToString, we then have to return a valid time string that represents the time that is input milliseconds after midnight on a day with no time changes.

So the problem boils down to whether "negative 15 minutes after midnight" is midnight or 23:45 of the previous day.

Comment 6

[Vincent Hilla [:vhilla]]

We can get the same issue also with stepUp and <input type=time min=17:00 value=23:45 step=900>

Comment 7

[Vincent Hilla [:vhilla]]

https://github.com/whatwg/html/issues/10503