Steps to reproduce:

for input with attributes type=button and list=(id of datalist), type is dynamically changed via javascript setAttribute on button click from button to text.

Actual results:

suggestions from datalist don't show up

Expected results:

suggestions from datalist show up (as happens in safari & chrome)

The Bugbug bot thinks this bug should belong to the 'Firefox::Address Bar' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Thanks for the testcase! Over to the DOM team for further triage.

The attribute change is observed here:
https://searchfox.org/mozilla-central/rev/b72e9d7d63bf499d1d8168291b93d4ec7fde236e/toolkit/components/satchel/nsFormFillController.cpp#148-149,160

And if it's liked to a datalist element, it'll start to autocomplete:
https://searchfox.org/mozilla-central/rev/b72e9d7d63bf499d1d8168291b93d4ec7fde236e/toolkit/components/satchel/nsFormFillController.cpp#1016,1028-1029

So anyway, this looks like a bug of autocomplete.

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

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Being in satchel this is effectively Form Manager.

So after further investigation, I believe two things cause this issue:

• An early return when the input field is not a text field. (https://searchfox.org/mozilla-central/source/toolkit/components/satchel/nsFormFillController.cpp#1005-1007)
• The focus state is not updated. (https://searchfox.org/mozilla-central/source/toolkit/components/satchel/nsFormFillController.cpp#1282-1283)

Since we never attach a mutation observer to the input if it's not a text input ( due to the early return ), we never pick up the change on the type attribute. Even if we did when we change the attribute the text input is not focused. This hints that we might also be handling the focus update wrong.

N.B: I reduced the example provided by OP to only a change from text to button input on click. The unexpected behavior still persists, but if you blur and then focus again everything works as expected.

Depends on D155245

Depends on D155246

Backed out 3 changesets (bug 1767250) for causing mochitest plain failures in toolkit/components/satchel/test/test_datalist_attribute_change.html

Backout link: https://hg.mozilla.org/integration/autoland/rev/f4a3b649b9122ae19e42f3b966a9281b337e308b

Push with failures

Failure log

LE. Also these android mochitest plain failures

:smolnar looking into it !

There are some r+ patches which didn't land and no activity in this bug for 2 weeks.
:issammani, could you have a look please?
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Sorry for the late reply. Just need to fix some tests and we should be good to go.

https://hg.mozilla.org/mozilla-central/rev/78fadd309a22
https://hg.mozilla.org/mozilla-central/rev/2c8ff4622a78