Issue #15317 has been updated by duerst (Martin Drst).


shevegen (Robert A. Heiler) wrote:
> Could a warning be issued as well, at the least for a transition period?

I warning might make sense, but then we would get into the question of whether we need a warning for those cases w
here property values changed (because obsoleting a property value essentially is the same as changing the value of the property for those characters that previously had the now obsoleted property value).

Often, property values only change for new characters (a defined character usually has different properties form an unassigned code point), which would not need a warning, and edge cases. That could lead to many superfluous warnings. It would also be quite difficult to implement, because the implementation would have to look at two or more sets of property files in parallel.

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Feature #15317: How to deal with obsolete property values in Unicode 11.0.0
https://bugs.ruby-lang.org/issues/15317#change-74938

* Author: duerst (Martin Drst)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 2.6
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http://www.unicode.org/versions/Unicode11.0.0/#Migration contains the following:

> Four Grapheme_Cluster_Break and Word_Break classes have become obsolete and are no longer used: E_Base, E_Modifier, Glue_After_Zwj, and E_Base_GAZ. Those values are still part of the enumeration of the property values, because stability constraints prevent removal of enumerated property values, even if obsolete; however, these are no longer assigned to any characters, and are no longer referred to explicitly by any rules in the algorithms.

For Ruby, we have to decide how to support (or not) these property values. The main choices are to throw an error or to just not match anything. The later seems preferable for backwards compatibility, but the relevant file (https://www.unicode.org/Public/UCD/latest/ucd/auxiliary/GraphemeBreakProperty.txt) does not mention these property values anymore.

I'm currently contacting other Unicode experts to find out whether there's some machine readable data for obsolete properties.

Your input is appreciated.



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