Return data source ids in Index::getDatasourceIds() without initalizing plugins

drunken monkey → made their first commit to this issue’s fork.

Thanks for reporting this problem!

As you already saw by the test failure, the Index class uses $this->datasourceInstances as the “source of truth” for its datasources. Keeping this consistent helps avoid a lot of thorny problems when changing index settings (see #2638116: Clean up caching of Index class method results (especially fields) → for background on this decision). For instance, a similar change as the one for removeDatasource() would have to be made to addDatasource() or getDatasourceIds() would return incorrect data when called after adding a datasource.

However, I guess this doesn’t really apply when the datasource plugins aren’t loaded yet, so maybe using either $datasourceInstances or $datasource_settings based on whether the former is initialized would work in all cases. The only “break” in functionality would now be that Index::getDatasourceIds() will never throw an exception, and since that exception wasn’t even documented I guess this is acceptable. As you say, it might even improve performance in rare cases.

Please give the new code in the MR a try!

Good thinking! I can confirm that the changes you made still mitigates the reported issue. Should I just RTBC this then? :thinking-face: