[XML-SIG] SAX exceptions are odd

[Jeremy Hylton]

>>>>> "MvL" == Martin v Loewis <martin@loewis.home.cs.tu-berlin.de> writes:

  >> If I get almost any other exception I get an error message that
  >> says something like: "not well-formed at None:1:7"
  >>
  >> Why is None being printed?  It gave me the initial impression
  >> that my error was no setting up parse call correctly.  I assumed
  >> that the None was the cause of the exception and that under
  >> normal circumstances it would have said something like "not
  >> well-formed at foo.xml:1:7".

  MvL> If the InputSource object has a proper system identifier, it
  MvL> should print it. It may be useful to print something different
  MvL> if it is None, e.g.
  MvL>    "not well-formed at <unknown>:1:7"

  MvL> If you did provide a file name, and it got lost somewhere -
  MvL> then that is a bug.

(It looks like you may have missed my second message on this subject.)
I did pass a filename that was lost.

  >> There are three different pieces of information separated by
  >> colons.  I am accustomed to the notation filename:line number,
  >> but not another colon for the cursor position.

  MvL> That's a matter of taste - you can write your own ErrorHandler
  MvL> if you don't like the output. I personally understood
  MvL> immediately that notation, as this is what Emacs supports as
  MvL> file locations.

It is a matter of taste.  We have been trying to improve the quality
and verbosity of error messages raised by Python code so that novices
have a better chance of understanding them.  It is no help to tell a
beginner: "The error messages produced by the xml packages are a tad
obscure.  Just write a subclass that makes the errors clearer."

  >> It would have been clearer, I think, if the message were more
  >> verbose and explained what each field was.

  MvL> For reproducability, it is probably best if it is terse - we
  MvL> would probably have a long debate on what it should look like
  MvL> if it had to change.

I don't understand what you mean by reproducability.  The ability to
reproduce an error message has nothing to do with whether it is terse
or verbose.

I liked the suggested error message that Lars proposed a *lot* better.

Jeremy