Add referenced_expressions

Author: jaynetics

CHANGELOG.md

@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- `#referenced_expressions`
+  - like `#referenced_expression`, but for multiplexing backrefs
+  - returns the `Group` expressions that are being referenced
+
 ### Fixed
 
 - fixed `#char` & `#codepoint` errors for single-digit hex escapes

lib/regexp_parser/expression.rb

@@ -34,6 +34,7 @@
 require_relative 'expression/methods/options'
 require_relative 'expression/methods/parts'
 require_relative 'expression/methods/printing'
+require_relative 'expression/methods/referenced_expressions'
 require_relative 'expression/methods/strfregexp'
 require_relative 'expression/methods/tests'
 require_relative 'expression/methods/traverse'

lib/regexp_parser/expression/classes/backreference.rb

@@ -1,25 +1,6 @@
 module Regexp::Expression
   module Backreference
-    class Base < Regexp::Expression::Base
-      attr_accessor :referenced_expression
-
-      def initialize_copy(orig)
-        exp_id = [self.class, self.starts_at]
-
-        # prevent infinite recursion for recursive subexp calls
-        copied = @@copied ||= {}
-        self.referenced_expression =
-          if copied[exp_id]
-            orig.referenced_expression
-          else
-            copied[exp_id] = true
-            orig.referenced_expression.dup
-          end
-        copied.clear
-
-        super
-      end
-    end
+    class Base < Regexp::Expression::Base; end
 
     class Number < Backreference::Base
       attr_reader :number

lib/regexp_parser/expression/classes/conditional.rb

@@ -7,26 +7,17 @@ def initialize
     end
 
     class Condition < Regexp::Expression::Base
-      attr_accessor :referenced_expression
-
       # Name or number of the referenced capturing group that determines state.
       # Returns a String if reference is by name, Integer if by number.
       def reference
         ref = text.tr("'<>()", "")
         ref =~ /\D/ ? ref : Integer(ref)
       end
-
-      def initialize_copy(orig)
-        self.referenced_expression = orig.referenced_expression.dup
-        super
-      end
     end
 
     class Branch < Regexp::Expression::Sequence; end
 
     class Expression < Regexp::Expression::Subexpression
-      attr_accessor :referenced_expression
-
       def <<(exp)
         expressions.last << exp
       end
@@ -54,11 +45,6 @@ def branches
       def reference
         condition.reference
       end
-
-      def initialize_copy(orig)
-        self.referenced_expression = orig.referenced_expression.dup
-        super
-      end
     end
   end
 end

lib/regexp_parser/expression/methods/referenced_expressions.rb

@@ -0,0 +1,28 @@
+module Regexp::Expression
+  module ReferencedExpressions
+    attr_accessor :referenced_expressions
+
+    def referenced_expression
+      referenced_expressions && referenced_expressions.first
+    end
+
+    def initialize_copy(orig)
+      exp_id = [self.class, self.starts_at]
+
+      # prevent infinite recursion for recursive subexp calls
+      copied = self.class.instance_eval { @copied_ref_exps ||= {} }
+      self.referenced_expressions =
+        if copied[exp_id]
+          orig.referenced_expressions
+        else
+          copied[exp_id] = true
+          orig.referenced_expressions && orig.referenced_expressions.map(&:dup)
+        end
+      copied.clear
+
+      super
+    end
+  end
+
+  Base.include ReferencedExpressions
+end

lib/regexp_parser/parser.rb

@@ -580,16 +580,19 @@ def active_opts
   # the instance of Group::Capture that it refers to via its number.
   def assign_referenced_expressions
     # find all referenceable and referring expressions
-    targets = { 0 => root }
+    targets = { 0 => [root] }
     referrers = []
     root.each_expression do |exp|
-      exp.is_a?(Group::Capture) && targets[exp.identifier] = exp
-      referrers << exp if exp.referential?
+      if exp.referential?
+        referrers << exp
+      elsif exp.is_a?(Group::Capture)
+        (targets[exp.identifier] ||= []) << exp
+      end
     end
-    # assign reference expression to referring expressions
+    # assign referenced expressions to referring expressions
     # (in a second iteration because there might be forward references)
     referrers.each do |exp|
-      exp.referenced_expression = targets[exp.reference] ||
+      exp.referenced_expressions = targets[exp.reference] ||
         raise(ParserError, "Invalid reference #{exp.reference} at pos #{exp.ts}")
     end
   end

spec/expression/methods/match_length_spec.rb

@@ -32,7 +32,7 @@
 
   specify('raises for missing references') do
     exp = RP.parse(/(a)\1/).last
-    exp.referenced_expression = nil
+    exp.referenced_expressions = nil
     expect { exp.match_length }.to raise_error(ArgumentError)
   end
 

spec/parser/refcalls_spec.rb

@@ -59,6 +59,14 @@
     expect(exp3.referenced_expression.to_s).to eq '(ghi)'
   end
 
+  specify('parse backref referenced_expressions (multiplex)') do
+    root = RP.parse('(?<a>A)(?<a>B)\\k<a>')
+    exp = root.last
+
+    expect(exp.referenced_expressions).to eq [root[0], root[1]]
+    expect(exp.referenced_expressions.map(&:to_s)).to eq ['(?<a>A)', '(?<a>B)']
+  end
+
   specify('parse backref call referenced_expression') do
     root = RP.parse('\\g<+1>(abc)\\g<+2>(def)(ghi)\\g<-2>')
     exp1 = root[0]