Applied mutation causes syntax error

Hi,

mutmut version: 1.1.0

I’m using Python 3.7 so in my code base I’m using this syntax: def except_to_bool(_func=None, *, exc=Exception, to=False):

When I apply mutmut it generates this mutant: def except_to_bool(_func=None, /, exc=Exception, to=False): which should not be generated as it produces syntax error.

If mutant should be generated here I imagine it should look like this: def except_to_bool(_func=None, exc=Exception, to=False): (simply remove star that enforces keyword arguments)

I even have test for this code (which is checking whether it is not possible to pass positional arguments to this function), but mutant still survives it. I think this is because mutant causes syntax error.

Either fix mutant generation with star, that enforces keyword arguments, or skip generating mutant at all in such case, please 😃

[boxed]

True, imports that are broken are for static analysis tools to handle. I’ll fix it.

[nklapste]

Maybe we should skip mutating any import lines.

Is there a way to detect lines defining import and from foo import bar statements within a parso.python.tree. If so we could add a rule to skip mutating these lines. I see no real value in messing up imports for mutation testing, it seems much too high level error injection to validate any real unit tests.