Right now the SourceDetectionTask constructor is responsible for adding flags_negative to the schema. So your proposal is that we make that the responsibility of the caller?

Hmm, I guess I am, but not intentionally. This ticket was about keeping it the responsibility of SourceDetectionTask, and I think that that requires the logic that was in the original ticket.

I'd be OK with the background code calling SourceDetectionTask with schema==None instead.

Ok, letting schema=None be valid in all cases and adding the flag field to the schema if and only if schema is not None and thresholdPolarity="both" sounds like the easiest way forward here.

I followed the last suggestion, though it was not clear to me that the flag should be set for thresholdPolarity=="negative".

Very short review of tickets/DM-903 on meas_algorithms: detection.py

Looks good! Sorry the review took me so long.

Not creating the flag for thresholdPolarity=='negative' seems correct to me - in that case all objects would have the same flag set, and hence it'd be pointless. In any case I think detecting only negative objects is quite rare; I'd be surprised if we use it all in production.