query_mutant_info for largest mutant id crash with ValueError when no mutants are present

[JonathanFoo0523]

When dredd is applied to a file where no mutations are possible, querying the mutation-info-file for the largest mutant ID results in an error. The following statement at line 326 in query_mutant_info.py:

print(max(list(mapping)))

fails with the error message ValueError: max() arg is an empty sequence.

Can we return something like -1 or just print a message to indicate that no mutants are present?

[afd]

Thanks for this report!

I think it makes more sense to return 0 to indicate that no mutants are present. That's what I have done in #269.

[JonathanFoo0523]

Thanks for this report!

I think it makes more sense to return 0 to indicate that no mutants are present. That's what I have done in #269.

I thought that we start counting mutant id from 0, and that the script returns the largest mutant id instead of number of mutants.

[JonathanFoo0523]

As an example, this should return 0:

int main() {
  printf("foo\n");
}

But this shouldn't:

int main() {}

[afd]

You're right - #271 opened to fix this; I think returning -1 is a reasonable solution.