Bad Default: Assembly.getArea() is 1.0

[john-science]

Over on this PR, I noted a strange point in the ARMI API.

When an Assembly has no children/Blocks, this method returns a "default area" of 1.0. Surely that should be an error? Or it should return None. Or it should return 0.0. Returning a valid numerical value just seems crazy.

armi/armi/reactor/assemblies.py

Lines 274 to 278 in f5fd79b

	except IndexError:
	runLog.warning(
	"{} has no blocks and therefore no area. Assuming 1.0".format(self)
	)
	return 1.0

[albeanth]

I say make it None. Rip the band aid off!

[jakehader]

This might be one of those "not all things in the composite pattern" should be implemented kind of thing. I'd be careful with areas though. Typically you make a composite and then add things to it. Not sure if it should be None either. Can you point to the code here?

[albeanth]

This might be one of those "not all things in the composite pattern" should be implemented kind of thing. I'd be careful with areas though. Typically you make a composite and then add things to it. Not sure if it should be None either. Can you point to the code here?

armi/armi/reactor/assemblies.py

Lines 274 to 278 in f5fd79b

	except IndexError:
	runLog.warning(
	"{} has no blocks and therefore no area. Assuming 1.0".format(self)
	)
	return 1.0

I'd say None with a runLog.warning would be appropriate. Or you could raise an error. That'd work too. If someone is creating an Assembly and then querying its area without a Block I think it would be a mistake and getting 1.0 would be unexpected. But maybe there's an application I'm not aware of where an Assembly can do "stuff" without a Block?