From 7efae1ca34a66bc2bc5503bb637678d7794c1aa6 Mon Sep 17 00:00:00 2001
From: Marc-Andre Lafortune <github@marc-andre.ca>
Date: Mon, 10 Aug 2020 11:55:17 -0400
Subject: [PATCH] Add `RegexpNode#each_capture` and `parsed_tree`

---
 CHANGELOG.md                         |  2 +-
 lib/rubocop.rb                       |  1 +
 lib/rubocop/ext/regexp_node.rb       | 46 ++++++++++++++++++++++++++++
 spec/rubocop/ext/regexp_node_spec.rb | 35 +++++++++++++++++++++
 4 files changed, 83 insertions(+), 1 deletion(-)
 create mode 100644 lib/rubocop/ext/regexp_node.rb
 create mode 100644 spec/rubocop/ext/regexp_node_spec.rb

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9e3a906b32aa..5f4b7f46f15c 100644
--- a/CHANGELOG.md
+++ b/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
 
diff --git a/lib/rubocop.rb b/lib/rubocop.rb
index c458bd750e80..69f3438bc677 100644
--- a/lib/rubocop.rb
+++ b/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'
 
diff --git a/lib/rubocop/ext/regexp_node.rb b/lib/rubocop/ext/regexp_node.rb
new file mode 100644
index 000000000000..3c8ede20f420
--- /dev/null
+++ b/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
diff --git a/spec/rubocop/ext/regexp_node_spec.rb b/spec/rubocop/ext/regexp_node_spec.rb
new file mode 100644
index 000000000000..bb1e4f13f932
--- /dev/null
+++ b/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