I was testing our current implementation, if we are autofilling and the user enters search mode, we should remove the autofilled part and in general never autofill when search mode is set to search.

That likely means setting allowAutofill to false when we start search mode searches.

As of bug 1647890 we don't autofill at all in search mode. We may actually want to autofill for the local one-offs. UX is going to think about it.

Comment 1 isn't entirely accurate. If there's currently an autofill result and then a one-off is clicked, we don't clear the autofill from the input. We don't fetch autofill for subsequent keystrokes, however. UX is still thinking over whether we should autofill for the local one-offs, but clearing autofill for search engine search modes is expected.

is there a test covering this?

No, I don't think so. We could add one when we fix this bug?

Update from UX: we should autofill when in a local search mode. So this bug encompasses implementing that behaviour, and clearing autofill when entering a remote search mode.

https://treeherder.mozilla.org/#/jobs?repo=try&revision=9e12181d69ec092e99584df60b81f0ba83204c9b

That conflicts with bug 1659204 though. Verdi said we shouldn't have heuristic results at all in local search mode, but in order to autofill, there has to be a heuristic result. What's the rationale for allowing autofill in local search mode?

(In reply to Drew Willcoxon :adw from comment #8)

That conflicts with bug 1659204 though.

In general heuristic results except autofill don't make sense in local search mode. I don't know what's the right answer here, imo there should be no heuristic, though I could accept autofill as an exception.
I'm wondering though what happens if we're are in local search mode with a search string and the user presses enter? Nothing? Searching wouldn't make sense. I guess that's the central part of bug 1659204.

I messaged Verdi about this issue.

Verdi confirms that we can show the autofill heuristic in local search modes. We should not show the search heuristic. This means that sometimes Enter will execute a search, and sometimes it will not. This is an acceptable trade-off.

https://hg.mozilla.org/mozilla-central/rev/83153a82d391

I verified this issue using 82.0a1 (2020-09-14) on macOS 10.13 and Windows 10 x64.
Adrian could you help me with Ubuntu verification?

Verified as fixed using latest Nightly 83.0a1 under Ubuntu 18.04 64-bit.