[XML-SIG] Specializing DOM exceptions

[Martin v. Loewis]

> My concern is that Python already has an IndexError and it is raised
> "naturally" (and efficiently) in a lot of places in minidom. At one
> point we had talked about formalizing a mechanism where Python
> exceptions stand for DOM exceptions.
> 
> So IndexSizeErr could be a subclass of Python's IndexError. Python
> "clients" could check for IndexError as they would in any other Python
> code. Those that want to treat the DOM stuff specially could do so. This
> would all be part of the Python-DOM mapping.

I don't see the value of this. When applications catch IndexError,
they normally do so to wrap a specific index access. In the Python
library, I found the following places where IndexError is caught:

        try:
            bp = Breakpoint.bpbynumber[number]
        except IndexError:
            return 'Breakpoint number (%d) out of range' % number
#############
            try:
                result.append(self[key])
            except IndexError:
                result.append(self.dict[key])
#############
                try:
                        self.response = args[0]
                except IndexError:
                        self.response = 'No response given'
...

I can't imagine a scenario where a DOM INDEX_SIZE_ERR and a Python
IndexError could likewise occur for a block of code, and would deserve
identical, specific treatment.

That said, if you think it is useful: go ahead and propose a specific
patch. It probably can't hurt.

Regards,
Martin