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Exceptions question #83
Description
In exceptions.py JSONPointerIndexError, JSONPointerKeyError, and JSONPointerTypeError use multiple inheritance to extend from both JSONPointerResolutionError, and IndexError, KeyError, and TypeError respectively.
Java doesn't have multiple class inheritance. I could get tricky with using interfaces to try to duplicate this, but first I wanted to ask what is your design goal with this class hierarchy? In test_json_pointer.py, you're catching the Python built-ins and not your custom Error classes. Is there a reason you are not just catching JSONPointerIndexError, JSONPointerKeyError, and JSONPointerTypeError?
Thanks!
- Rob
Activity
jg-rp commentedon Aug 2, 2025
Hi Rob,
Inheriting from
IndexError,KeyErrorandTypeErrorwas an afterthought and not part of the original design. I wanted to cater for Python users that might expect handling standard exceptions to work as if they're accessing a dictionary or list. A bit like being able to catchIndexOutOfBoundsExceptionor a custom exception with an independent class hierarchy in Java.Testing the standard exceptions in
test_json_pointer.pyand not those inheriting fromJSONPointerResolutionErroris an oversight on my part.I think you could safely ignore multiple inheritance here and go with something like this:
The important part being that
JSONPointerResolutionErrorand its subclasses only occur when resolving a JSON Pointer, not when parsing a JSON Pointer from a string (I can see one place where I'm failing to do this).Depending on how strict you're being with your port, you could instead choose to follow Jackson's example and use a "missing" object to indicate the absence of a node instead of throwing exceptions, a bit like
JsonNode.path()does, if that would make more sense to your average Java developer (it's been a long time since I wrote any Java 🤷♂️).Cheers,
James