Add RegexpNode#each_capture and parsed_tree

CHANGELOG.md

@@ -15,7 +15,7 @@
 * Add new `Lint/TrailingCommaInAttributeDeclaration` cop. ([@drenmi][])
 * [#8578](https://github.com/rubocop-hq/rubocop/pull/8578): Add `:restore_registry` context and `stub_cop_class` helper class. ([@marcandre][])
 * [#8579](https://github.com/rubocop-hq/rubocop/pull/8579): Add `Cop.documentation_url`.  ([@marcandre][])
-
+* [#8510](https://github.com/rubocop-hq/rubocop/pull/8510):  Add `RegexpNode#each_capture` and `parsed_tree`. ([@marcandre][])
 
 ### Bug fixes
 

lib/rubocop.rb

@@ -9,6 +9,7 @@
 require 'unicode/display_width/no_string_ext'
 require 'rubocop-ast'
 require_relative 'rubocop/ast_aliases'
+require_relative 'rubocop/ext/regexp_node'
 
 require_relative 'rubocop/version'
 

lib/rubocop/ext/regexp_node.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Ext
+    # Extensions to AST::RegexpNode for our cached parsed regexp info
+    module RegexpNode
+      ANY = Object.new
+      def ANY.==(_)
+        true
+      end
+      private_constant :ANY
+
+      class << self
+        attr_reader :parsed_cache
+      end
+      @parsed_cache = {}
+
+      # @return [Regexp::Expression::Root, nil]
+      def parsed_tree
+        return if interpolation?
+
+        str = content
+        Ext::RegexpNode.parsed_cache[str] ||= begin
+                                                Regexp::Parser.parse(str)
+                                              rescue StandardError
+                                                nil
+                                              end
+      end
+
+      def each_capture(named: ANY)
+        return enum_for(__method__, named: named) unless block_given?
+
+        parsed_tree&.traverse do |event, exp, _index|
+          yield(exp) if event == :enter &&
+                        named == exp.respond_to?(:name) &&
+                        exp.respond_to?(:capturing?) &&
+                        exp.capturing?
+        end
+
+        self
+      end
+
+      AST::RegexpNode.include self
+    end
+  end
+end

spec/rubocop/ext/regexp_node_spec.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+require 'timeout'
+
+RSpec.describe RuboCop::Ext::RegexpNode do
+  let(:source) { '/(hello)(?<foo>world)(?:not captured)/' }
+  let(:processed_source) { parse_source(source) }
+  let(:ast) { processed_source.ast }
+  let(:node) { ast }
+
+  describe '#each_capture' do
+    subject(:captures) { node.each_capture(**arg).to_a }
+
+    let(:named) { be_instance_of(Regexp::Expression::Group::Named) }
+    let(:positional) { be_instance_of(Regexp::Expression::Group::Capture) }
+
+    context 'when called without argument' do
+      let(:arg) { {} }
+
+      it { is_expected.to match [positional, named] }
+    end
+
+    context 'when called with a `named: false`' do
+      let(:arg) { { named: false } }
+
+      it { is_expected.to match [positional] }
+    end
+
+    context 'when called with a `named: true`' do
+      let(:arg) { { named: true } }
+
+      it { is_expected.to match [named] }
+    end
+  end
+end