Lacking unit tests for this (documented) functionality makes it harder
for alternate Python runtimes to correctly provide it.  Plus, if it's
not tested, it might not work.

I tried to write tests for the feature since I recently used it and
thought it would be pretty straightforward.  However, I failed.  expat
inscrutably refuses to call the external entity ref handler I provided
in my test.  Attached is my attempted, in case anyone feels like helping
complete it.

You need to make two changes:
1. Enable parsing of parameter entities in the first place, e.g. through
SetParamEntityParsing(XML_PARAM_ENTITY_PARSING_ALWAYS)
2. Pass a well-formed document, e.g.
"<?xml version='1.0'?><element/>"

Thanks, that helped a bunch.  I'm sure it would have taken me a long
time to find SetParamEntityParsing(XML_PARAM_ENTITY_PARSING_ALWAYS). 
Perhaps it would also be good to expand the pyexpat documentation to
cover that method and parameter (unless it's there already and I missed
it, but I don't think so).

Can you provide an update patch?

Here's the version I have now.  I don't think it's complete, but it
finishes the test started in the previous patch, and the test passes.

To clarify, I'll probably work on this patch a bit more later, adding a
few more tests for related behavior.

Here's a new patch which adds SetParamEntityParsing to the pyexpat
library docs and adds another test for external entity reference
handling.  This is probably all I'll do on this ticket.

Hi all, I think this patch would be nice to be applied, but before start working on it (like adapt it to new code & stuff), I'd like to know if we are really targetting 2.7 or should we instead targer 3.3.

Cheers, Sandro

I don't think we should adding tests to 2.7, perhaps unless there are also fixes for it. So targetting 3.3+ only seems reasonable.

Ok, I've changed the version field and refreshed the patch against py3k.

Doc patch committed in r87762.

Ok, I've changed "assertEquals" to "assertEqual" and committed the tests in r87765. Thank you!