The kinds of errors to be handled in this ticket actually fall into two categories, which we should deal with differently:

• For problems that cause all measurements of a certain type to fail on an exposure, because something is wrong with that exposure that can be determined up front (e.g. no PSF), we should add a way (perhaps a plugin class member) a plugin can use to declare which properties of an exposure must be met for it to run. The measurement task could then check those properties when processing a new exposure, and then raise an exception before calling any plugins. (I do think we want to raise a fatal exception here, because it indicates either a logic bug in the configuration or a pretty serious failure in a previous processing stage. If we need to, we can have a config option to proceed anyway, and then have the measurement task skip the plugins that it knows can't handle that exposure.

• For common problems that can only be determined when an algorithm is running (including looking for e.g. NaNs, since we don't want to do that up front over the entire exposure), we should define a custom exception class for that kind of failure that can be thrown by the plugins. This should inherit from MeasurementError and hence always set a bit. In some cases we may want to have config options on the task to control whether to suppress, warn, or propagate up these exceptions.

This is actually a pretty easy review. I'm giving it to you so that you can see what the behavior is going to be and can comment on the exception handling.

checkin was to u/pgee/DM-461

pgeepc2:/sandbox2/pgee/mylsst7/Linux64/mb12> git diff --stat origin/master
include/lsst/meas/base/GaussianFlux.h | 2 –
include/lsst/meas/base/Inputs.h | 15 +++++++++++++--
include/lsst/meas/base/PsfFlux.h | 2 –
include/lsst/meas/base/SdssCentroid.h | 2 –
include/lsst/meas/base/exceptions.h | 26 ++++++++++++++++++++++++++
python/lsst/meas/base/base.py | 2 +-
python/lsst/meas/base/baseLib.i | 1 +
src/GaussianFlux.cc | 5 ++---
src/PsfFlux.cc | 5 ++---
src/SdssCentroid.cc | 5 ++---
tests/testGaussianFluxBasic.py | 1 -
tests/testPsfFlux.py | 5 +----
tests/testPsfFluxBasic.py | 1 -
tests/testSdssCentroidBasic.py | 1 -
14 files changed, 48 insertions, 25 deletions

Looks good to merge, no comments.

Oops, for some reason I thought this review was assigned to me.

I agree with Jim. This looks great. Please merge.