Undefined behaviour when clicking a label which inside modal dialog that activates the form control

[sefeng211]

We have a WPT for modal dialog which expects clicking the label which inside the modal dialog could trigger the click event at the input element which is outside of the modal dialog.

However this behaviour seems undefined since the input element is inert.

@smaug---- @emilio @domenic @nt1m

[smaug----]

And clicking on label element triggering a click on some other element is undefined in general, or rather, it is said to be platform specific.

[nt1m]

Looking at the spec for inert: https://html.spec.whatwg.org/multipage/interaction.html#inert-subtrees

The 4 bullet points make the test as it is correct.

However, in the following note, it says: "Inert nodes that are commands will also get disabled.", so this is basically up to: is checking a checkbox a command?

[nt1m]

For text inputs, the note says inert elements cannot be focused, so that does mean clicking the label should fail to focus the text input.

It is definitely more ambiguous for other input types though.

[scottaohara]

per my PR @nt1m, that specific bit of the text indicating that the element(s) become "disabled" is changing - #8122

Does this need to change back? I made the change because of situations where content (form controls) are within an inert subtree but they still need to participate in a form submission. e.g., a stepped form where different portions of the form are set off-screen and prevented from being accessed when not in view (or partially in view) via the inert attribute. Those form controls shouldn't be operable / accessible to users so long as they are inert, but they also shouldn't be 'disabled' - unless the term is being used differently in this context? Am I incorrect on any of my understanding here?

[smaug----]

The 4 bullet points make the test as it is correct.

Nothing says that clicking a label should click the form control, so the test is relying on undefined behavior. (This part has nothing to do with inert)