Since Lea explained this ticket to me in person, here's a quick rephrased explanation of this ticket:

Steps to reproduce:

1. Make sure you are logged in and go to: https://de.wikipedia.org/w/index.php?search=&title=Spezial%3ASuche&go=Artikel
2. Select all namespaces by clicking on "Alle" and perform a search with a search term of your choice.
   1. You should now be able to see all namespaces listed in the URL while on the search result page
3. Deselect all namespaces by clicking on "Alle" again and perform another search.
4. Since no namespaces were selected, the search defaults back to the namespaces you have stored in your account.

After the last step, it will show you the search results with the namespaces you have "remembered" in your account but the URL does not reflect that. Instead, the URL will look like this, completely missing the namespace parameters that were actually used by your user defaults:

https://de.wikipedia.org/w/index.php?search=Test&title=Spezial%3ASuche&profile=advanced&fulltext=1&advancedSearch-current=%7B%7D

The issue is that if people share this URL now, the search results will look different depending on what individual users have selected to be their default namespaces. The task of this ticket is to ensure that currently selected namespaces are always reflected in the URL, even if the search uses the default namespaces of the current user.

Change 496163 had a related patch set uploaded (by Tim Eulitz; owner: Tim Eulitz):
[mediawiki/extensions/AdvancedSearch@master] Ensure namespaces are always part of search URLs

https://gerrit.wikimedia.org/r/496163

Change 496163 had a related patch set uploaded (by WMDE-Fisch; owner: Tim Eulitz):
[mediawiki/extensions/AdvancedSearch@master] Ensure namespaces are always part of search URLs

https://gerrit.wikimedia.org/r/496163

Change 496163 merged by jenkins-bot:
[mediawiki/extensions/AdvancedSearch@master] Ensure namespaces are always part of search URLs

https://gerrit.wikimedia.org/r/496163