EDIT: may be duplicate of https://blueprints.launchpad.net/murano/+spec/throw-correct-exception
Within the PL processing (particular executor.py, expressions.py) there's use of Python built-in exceptions (SyntaxError, ValueError, TypeError). These exceptions are for use in tightly-defined scenarios, so while their use makes sense looking at their names, it causes confusion when debugging because developers (well, me, anyway) are used to seeing them in a different context.
I suggest adding to dsl/exceptions.py equivalents (DSLSyntaxError etc), and at the same time providing more diagnostic information, since the stacktraces are often not useful because they're tens of levels deep. As an example from executor.py L175, instead of:
if name not in arguments_scheme:
raise TypeError()
Use:
if name not in arguments_scheme:
raise DSLTypeError("'%s' is not in the recognized arguments (%s)" % (name, argument_scheme))
The calling code can turn this error into something else if necessary but preserve the information.
In addition, exception handling blocks that don't log a message should have a comment explaining how they are handling the error if it isn't obvious.
Fix proposed to branch: master
Review: https:/