Issue #19317 has been updated by zverok (Victor Shepelev). Oh, OK, I see where you are coming from (the formal correctness of correspondence to Unicode standard/known standard definitions), while I was operating in vague and informal terms "what the user might've meant". I still don't know what's the "right" way to handle "turkic" problem more formally. Unicode standards seem to kind of ignore the problem, as far as I can tell, though I am not very well-versed in this. At least [SpecialCasing.txt](https://www.unicode.org/Public/UCD/latest/ucd/SpecialCasing.txt) uses the informal term "turkic" in the comments: ``` # Preserve canonical equivalence for I with dot. Turkic is handled below. ``` ...but then just introduces two independent lines for Turkish and Azeri, ignoring any other turkic langs: ``` # Turkish and Azeri # I and i-dotless; I-dot and i are case pairs in Turkish and Azeri # The following rules handle those cases. 0130; 0069; 0130; 0130; tr; # LATIN CAPITAL LETTER I WITH DOT ABOVE 0130; 0069; 0130; 0130; az; # LATIN CAPITAL LETTER I WITH DOT ABOVE # ...and so on ``` ---------------------------------------- Feature #19317: Unicode ICU Full case mapping https://bugs.ruby-lang.org/issues/19317#change-101143 * Author: noraj (Alexandre ZANNI) * Status: Assigned * Priority: Normal * Assignee: duerst (Martin Dürst) ---------------------------------------- As announced in [Case Mapping](https://docs.ruby-lang.org/en/master/case_mapping_rdoc.html#label-Default+Ca...), Ruby support for Unicode case mapping is not complete yet. Unicode supports in Ruby is pretty awesome, it works by default nearly everywhere, things are implemented the right way and works as expected by the UTRs. But some features are still missing. To reach [ICU Full Case Mapping support](https://unicode-org.github.io/icu/userguide/transforms/casemappings.html#ful...), a few points need to be enhanced. ### context-sensitive case mapping * [ ] cf. [Table 3-17 (Context Specification for Casing) of the Unicode standard](https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf) and [ucd/SpecialCasing.txt](https://www.unicode.org/Public/UCD/latest/ucd/SpecialCasing.txt). ```ruby "ΣΣ".downcase # returns σσ instead of σς ``` Output examples in ECMAScript: ``` Σ ➡️ σ Σa ➡️ σa aΣ ➡️ aς aΣa ➡️ aσa ΣA ➡️ σa aΣ a ➡️ aς a Σ1 ➡️ σ1 aΣ1 ➡️ aς1 ΣΣ ➡️ σς ``` ## language-sensitive case mapping * [ ] Lithuanian rules * [x] Turkish and Azeri ```ruby "I".downcase # => "i" "I".downcase(:turkic) # => "ı" "I\u0307".upcase # => "İ" "I\u0307".upcase(:lithuanian) # => "İ" instead of "I" ``` * [ ] using some standard locale / language codes Also, it's true that for now there are only a few language-sensitive rules (for Lithuanian, Turkish and Azeri) but why: - adding a `:turkic` symbol and not a `:azeri`? - using full english arbitrary (why `turkic` and not `turkish`?) language name rather than some [ICU locale IDs](https://unicode-org.github.io/icu/userguide/locale/)? - Language code ISO-639 standard - Script code Unicode ISO 15924 Registry - country code ISO-3166 standard So I would rather see something like that ```ruby "placeholder".upcase(locale: :tr_TR) "placeholder".upcase(lang: :tr) ``` -- https://bugs.ruby-lang.org/