[ruby-core:78359] [Ruby trunk Feature#12831] /\X/ (extended grapheme cluster) can't pass unicode.org's GraphemeBreakTest

Issue #12831 has been updated by Shyouhei Urabe.


We looked at this issue in todays developer meeting and assigned it to Yui.  But no one there had implementation of this.  It might need some time.  Stay tuned!

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Feature #12831: /\X/ (extended grapheme cluster) can't pass unicode.org's GraphemeBreakTest
https://bugs.ruby-lang.org/issues/12831#change-61719

* Author: Fumiaki Matsushima
* Status: Assigned
* Priority: Normal
* Assignee: Yui NARUSE
----------------------------------------
I'm trying to replace Rails's grapheme implementation (http://api.rubyonrails.org/classes/ActiveSupport/Multibyte/Unicode.html#method-i-unpack_graphemes) with Ruby's extended grapheme cluster (/X/).
https://github.com/rails/rails/issues/26743

I noticed that Ruby's grapheme cluster can't pass unicode.org's GraphemeBreakTest.

Following test script will fail on Ruby 2.2/2.3

~~~ ruby
require 'rubygems'
require 'open-uri'
require 'test/unit'

UNICODE_VERSION =
  if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new("2.3.0")
    "8.0.0"
  else
    "7.0.0"
  end

class TestGrapheme < Test::Unit::TestCase
  # https://github.com/rails/rails/blob/v5.0.0.1/activesupport/test/multibyte_grapheme_break_conformance_test.rb#L37
  def test_breaks
    each_line_of_break_tests do |*cols|
      *clusters, comment = *cols
      string = clusters.map {|c| c.pack("U*") }.join
      assert_equal clusters, string.scan(/\X/).map(&:codepoints), comment
    end
  end

  def each_line_of_break_tests(&block)
    lines = 0
    max_test_lines = 0 # Don't limit below 21, because that's the header of the testfile
    URI.parse("http://www.unicode.org/Public/#{UNICODE_VERSION}/ucd/auxiliary/GraphemeBreakTest.txt").open do |f|
      until f.eof? || (max_test_lines > 21 && lines > max_test_lines)
        lines += 1
        line = f.gets.chomp!
        next if line.empty? || line.start_with?("#")

        cols, comment = line.split("#")
        # Cluster breaks are represented by ÷
        clusters = cols.split("÷").map { |e| e.strip }.reject { |e| e.empty? }
        clusters = clusters.map do |cluster|
          # Codepoints within each cluster are separated by ×
          codepoints = cluster.split("×").map { |e| e.strip }.reject { |e| e.empty? }
          # codepoints are in hex in the test suite, pack wants them as integers
          codepoints.map { |codepoint| codepoint.to_i(16) }
        end

        # The tests contain a solitary U+D800 <Non Private Use High
        # Surrogate, First> character, which Ruby does not allow to stand
        # alone in a UTF-8 string. So we'll just skip it.
        next if clusters.flatten.include?(0xd800)

        clusters << comment.strip

        yield(*clusters)
      end
    end
  end
end
~~~

https://gist.github.com/mtsmfm/38f46882c3d4ccde35c269594fc24ebc

I found an issue on Onigmo (https://github.com/k-takata/Onigmo/issues/46)
but I couldn't on bugs.ruby-lang.org so I created this ticket.

I'm unfamiliar with grapheme so please tell me if I get something wrong.



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