Ensure that maximum normalised distance is <= 1 and ...

[juliangilbey]

textdistance is currently failing its test-suite on arm64 machines with Python 3.10, which is causing me problems on Debian. I have managed to track down the first of these bugs (and there are at least two more to come): there are some algorithms that use upper() before comparing the strings. As noted in the code already, though these algorithms were designed for English (ASCII only), this can cause upper() to change the length of the string if using non-English characters. And hypothesis does this when testing. This can result in the normalised distance being greater than 1. This patch addresses this by ensuring that the distance returned from the relevant algorithms is no greater than self.maximum().

A second issue which arose when doing this was calculating the maximum distance for Editex(); the current function for calculating the maximum does not give the correct answer if match_cost > mismatch_cost, for example. But this would be a silly situation: why would we penalise matching characters more than mismatching ones? There are two ways of resolving this: the first is to calculate the maximum distance using max(match_cost, group_cost, mismatch_cost), the second is to force the inequalities match_cost <= group_cost <= mismatch_cost. I have gone for the latter option in this patch.

All being well, there will be more patches to come in the next few weeks as I get to the bottom of them!

[orsinium]

Thank you! Seems legit :)

[orsinium]

Then I'll wait for the remaining patches before making the release 👍🏿