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require_relative 'base'
class JsRegex
module Converter
#
# Template class implementation.
#
class MetaConverter < JsRegex::Converter::Base
DOT_EXPANSION = '(?:[\uD800-\uDBFF][\uDC00-\uDFFF]|[^\n\uD800-\uDFFF])'
ML_DOT_EXPANSION = '(?:[\uD800-\uDBFF][\uDC00-\uDFFF]|[^\uD800-\uDFFF])'
# Possible improvements for dot conversion:
#
# In ES2015, the 'u' flag allows dots to match astral chars. Unfortunately
# the dot keeps matching lone surrogates even with this flag, so the use
# of an expansion is still necessary to get the same behavior as in Ruby.
#
# ES2018 has the dotall flag 's', but it is tricky to use in conversions.
# 's' activates matching of BOTH astral chars and "\n", whereas the dot in
# Ruby doesn't match "\n" by default, and even with the 'm' flag set on
# the root, subexps might still exclude "\n" like so: /.(?-m:.)./m
private
def convert_data
case subtype
when :alternation
convert_alternatives
when :dot
expression.multiline? ? ML_DOT_EXPANSION : DOT_EXPANSION
else
warn_of_unsupported_feature
end
end
def convert_alternatives
kept_any_previous_branch = nil
convert_subexpressions.transform do |node|
unless dropped_branch?(node)
node.children.unshift('|') if kept_any_previous_branch
kept_any_previous_branch = true
end
node
end
end
def dropped_branch?(branch_node)
branch_node.children.any? && branch_node.children.all?(&:dropped?)
end
end
end
end
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