@tsteur The PR as is would actually be good to merge and would possibly solve some update issues where one of the dimension file couldn't be removed.

But I'm currently thinking on how to best check for removed dimensions, to avoid such issues in the future if the list isn't updated. But actually I don't see a good way for doing that. We could check the git history for removed files and check if one of those files was a dimension (using it's own database column). But actually I'm not sure if it's worth the effort.

Also I wonder if we actually shouldn't remove the dimension version in option table with an update that removes a dimension.
For people where the updater didn't remove the file, that might actually cause a update adding the column again. So might be not that good, but at least would avoid such issues 🤔

@sgiehl we wouldn't want to look through git history.

Could we add something like https://github.com/matomo-org/matomo/blob/4.0.5/plugins/Widgetize/tests/System/WidgetTest.php#L57-L75 where we have a list of all available dimensionIds. When one dimension is removed, we'd expect the test to fail and would mention something like "if the dimension was removed on purpose you now need to add it to the list of removed dimensions" or similar. Basically we'd maintain a hard coded list of dimensions we have in the test. So we notice when one is added or removed.

Haven't thought this through but maybe that would work.

Re removing options for these columns: It be a problem indeed if it was to try to add the columns again and again. Maybe instead the above test could help in the future as well to not add the same column name again? I wouldn't spend too much time on it but might be worth a check like if we had a list of getDeprecatedDimensions() and getDeprecatedColumns() then we could have a test that makes sure we don't add the same ones again in the future so the option could still exist.

@tsteur I've updated the PR. For now the test only checks the dimensions holding a column definition. Guess those dimensions might make the most trouble when removed. Or do you think we should maintain a list of all dimensions?

@tsteur applied the feedback