caseFold.equals doesn't implement full case folding

[babolivier]

The unicode spec on case folding specifies that ß and ẞ (its uppercase version) should equal to ss when doing a full case folding, as shown by the Python implementation:

>>> 'ẞ'.casefold()
'ss'
>>> 'ß'.casefold()
'ss'

However, when trying to compare those two characters to their casefolded version using caseFold.equals, this happens:

> casefold.caseFold.equals("ẞ", "ss")
false
> casefold.caseFold.equals("ß", "ss")
false

[JoBrad]

Hey, thanks for the feedback! I am in the middle of converting this to make better use of ES6 modules, and updating the string comparison was also on my list.

If you have an improvement for it, feel free to submit a PR.

[joshxyzhimself]

Hi, @babolivier, if you are looking for full case folding I tried implementing the following according to the spec:

#  A. To do a simple case folding, use the mappings with status C + S.
#  B. To do a full case folding, use the mappings with status C + F.

• https://www.unicode.org/Public/14.0.0/ucd/CaseFolding.txt

import { simple_casefold, full_casefold, special_casefold } from './casefold.mjs';

console.log(simple_casefold('\u0041 \u00DF \u0130'));
console.log(full_casefold('\u0041 \u00DF \u0130'));
console.log(special_casefold('\u0041 \u00DF \u0130'));
console.log(`MASSE === Maße: ${full_casefold('MASSE') === full_casefold('Maße')}`);

user@device:~/modules$ node ./casefold.test.mjs 
a ß İ
a ss i̇
a ss i
MASSE === Maße: true

• https://github.com/joshxyzhimself/modules/blob/main/casefold.mjs
• https://github.com/joshxyzhimself/modules/blob/main/casefold.test.mjs

I used Unicode 14.0.0 because 15.0.0 is still in Draft for this year until it's release on September. It is in ECMAScript Modules (.mjs) format but can easily be converted to CommonJS (.js/.cjs) format. Also requesting for comments on possible improvements. Thank you.