Allow etaMin, etaMax bounds in Geant4IsotropeGenerator and DDSim/Helper/Gun.py

[wdconinc]

Just ran a lot of simulations with sim.gun.etaMin = -1 and sim.gun.etaMax = +1... which turned out to not be a setting that exists in DD4hep, but DDSim didn't complain about it.

This issue reports two aspects:

• using a steering file with non-existent settings did not lead to complaints (not sure how dd4hep would find out),
• I'm going to be contributing etaMin and etaMax as a PR (which is why I picked "new feature" as category).

To reproduce:

cat << EOF > gamma_10GeV_eta.steer
from DDSim.DD4hepSimulation import DD4hepSimulation
from g4units import mm, GeV, MeV, degree
SIM = DD4hepSimulation()
SIM.gun.energy = 10*GeV
SIM.gun.particle = "gamma"
SIM.gun.position = (0.0, 0.0, 0.0)
SIM.gun.direction = (0.0, 0.0, 1.0)
SIM.gun.distribution = "uniform"
SIM.gun.etaMin = -1.0
SIM.gun.etaMax = +1.0
EOF
ddsim --compactFile $DD4hepINSTALL/DDDetectors/compact/SiD.xml -G -N 10 --steeringFile gamma_10GeV_eta.steer 

[andresailer]

Dynamically adding properties to instances is of course a core python feature. We can probably prevent this with __slots__?

[wdconinc]

__slots__ seems to have a clunky interface compared to __dict__. Can we compare the length of __dict__ immediately after the definition of the Helper with the length after parsing options? If it is different, we must have used an unsupported variable name. ConfigHelper would do the initial count.

[MarkusFrankATcernch]

Can we close this issue?

[andresailer]

Still work to do.

[andresailer]

I implemented a check for unknown properties.