Issue 277: make toCaseFold idempotent #293
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phadej
commented
Aug 25, 2020
| foldMapping '\x10c7' s = Yield '\x2d27' (CC s '\x0000' '\x0000') | ||
| -- GEORGIAN CAPITAL LETTER AEN | ||
| foldMapping '\x10cd' s = Yield '\x2d2d' (CC s '\x0000' '\x0000') | ||
| -- NOT FOLDED TO toLower '\x13a0' |
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This is an example of where toLower doesn't work. '\x13a0 is a Cherokee Letter A which case folds to itself (i.e. stays uppercase!).
This file has also plenty of added letters with known name, i.e. in CaseFolding.txt. Those are capital letters for which there is folding to lowercase, but toLower doesn't always fold them. Adding them makes toCaseFold behave uniformly independently of base version.
- Add property and regression test that toCaseFold should be idempotent - Add scripts/tests.sh to run tests with all GHCs. There are plenty of setup commands to pass. - Rework CaseFolding.hs so it considers that toLower behaves differently with different GHCs, and therefore fallbacks to it only when it behaves consistently. For that purpose a helper `scripts/Dump.hs` is added. Also MurMurVariant is quick hash which works with all GHCs, it should notice if there are changes in the behaviour. Note: `toLower`, `toUpper`, and `toTitle` would benefit from using dumped database as well. This commit is already quite big, so that is left for a follow up.
Merged
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I won't fix the conflicts |
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This PR currently only adds a test for #227. Expectedly it fails (when you run locally, run with
-p idemp -a 10000to run just the new tests enough times to find a counterexample).toCaseFoldshould be idempotent, but it doesn't seem to be.