Messages for the next page appear on the current one because of prefetching

[WofWca]

Describe the issue

In #7565 we added next page prefetching, and it appears to affect the current page in a weird way. See reproduction.

I already tried

• I've read and searched the documentation.
• I've searched for similar issues in this repository.

Steps to reproduce the behavior

1. Use a Chromium-based browser for easier reproduction.
2. Go to /translate, to the last page of the search (e.g. https://hosted.weblate.org/translate/weblate/application/en/?&offset=2724)
3. Click "Previous page", or refresh the page.
4. A "The translation has come to an end." message will appear.

Instead of step 3 you can even open any hosted Weblate page in a new tab, it will show the message, lol.

Expected behavior

Messages only appear for the pages they're supposed to be displayed on.

Screenshots

Exception traceback

No response

How do you run Weblate?

weblate.org service

Weblate versions

No response

Weblate deploy checks

No response

Additional context

weblate/weblate/templates/base.html

Line 23 in 4222059

<link rel="next prefetch" href="{{ next_unit_url }}" />

weblate/weblate/trans/views/edit.py

Lines 560 to 561 in 4b2e079

	if not 0 < offset <= num_results:
	messages.info(request, _("The translation has come to an end."))

[WofWca]

Looks like it's from a package.

weblate/weblate/utils/messages.py

Lines 39 to 42 in 6f2fd4e

	def info(request, message, extra_tags=""):
	"""Add a message with the ``INFO`` level."""
	if request is not None:
	add_message(get_request(request), constants.INFO, message, extra_tags)

weblate/weblate/utils/messages.py

Line 25 in 6f2fd4e

from django.contrib.messages import add_message, constants

I thought we could maybe bail inside the info function if the request has the prefetch header.

[nijel]

That would just silently discard the message...

But the message itself is not the problem, this also deletes cached search results from the session, so the search won't be reproducible anymore, what could break translating the last string (if the search would now return less results).

weblate/weblate/trans/views/edit.py

Lines 561 to 564 in 563f0ce

	messages.info(request, _("The translation has come to an end."))
	# Delete search
	del request.session[search_result["key"]]
	return redirect(obj)

I think disabling prefetching is the safest way to go for now, I will revert 4222059.

[github-actions]

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[WofWca]

That would just silently discard the message...

Oh.... Right... Forgot that the prefetched page actually needs to be used. 😅