[TIP] Are extensions needed for coverage required?

[Uri Okrent]

Ned Batchelder <ned <at> nedbatchelder.com> writes:
> program.  To reduce the burden, coverage.py has a trace function written 
> in C.  If for whatever reason you can't compile that C extension, 
> coverage.py will fall back to a Python implementation, which is what 


Hi Ned, I think I may have found a bug in the python implementation, but I'm not 
sure.  I normally run my unit tests through coverage.  I just wrote some code
and the tests were passing, but when I tried to run coverage the same tests
would fail.

Here is the error:

    criteria_set.add(active_criteria)
TypeError: unhashable type: 'dict'

This seems impossible because the (rather squirrely) code in question is this:

144     criteria_set = set()
...
148             active_criteria = []
149             for criterion in criteria_keys:
150                 if criterion in selection_set:
151                     active_criteria.append(criteria[criterion])
152                 else:
153                     active_criteria.append(None)
154             active_criteria = tuple(active_criteria)
155             # add unique criteria set tuples to the list of criteria sets
156             criteria_set.add(active_criteria)

And of course, the tests pass unless I run them under coverage
(`env PYTHONPATH=. coverage run /usr/bin/unit2 discover -s test` vs. 
`env PYTHONPATH=. /usr/bin/unit2 discover -s test`).

First thing I tried was upgrading my version of coverage from 3.5.1 to 3.5.3,
but that made no difference.  I did notice, during the installation the error
regarding the extension, and so because I'm anal, I went back and apt-get
install python-dev and then reinstalled coverage, and this time the 
coverage.tracer extension was successfully built.

Just for the heck of it I ran coverage again, and lo and behold, all my tests
are passing now.

By the way, I really appreciate the awesome work you do with coverage.

Thanks,

Uri