From 6dce0e647a52b31fe9011ebda232d71afd3f140e Mon Sep 17 00:00:00 2001
From: Marc-Andre Lafortune <github@marc-andre.ca>
Date: Wed, 1 Jul 2020 14:25:29 -0400
Subject: [PATCH] [Fixes #44] Use parser's new emit_forward_arg by default

---
 CHANGELOG.md               | 4 ++++
 README.md                  | 5 +++--
 lib/rubocop/ast/builder.rb | 2 ++
 rubocop-ast.gemspec        | 2 +-
 spec/spec_helper.rb        | 5 ++++-
 5 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a5de8c081..52f19d686 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,10 @@
 
 * [#50](https://github.com/rubocop-hq/rubocop-ast/pull/50): Support find pattern matching for Ruby 2.8 (3.0) parser. ([@koic][])
 
+### Changes
+
+* [#44](https://github.com/rubocop-hq/rubocop-ast/issue/44): **(Breaking)** Use `parser` flag `self.emit_forward_arg = true` by default. ([@marcandre][])
+
 ## 0.1.0 (2020-06-26)
 
 ### New features
diff --git a/README.md b/README.md
index 604ee63de..e5eda6ce2 100644
--- a/README.md
+++ b/README.md
@@ -35,8 +35,9 @@ See the [docs site](https://docs.rubocop.org/rubocop-ast) for more details.
 
 ### Parser compatibility switches
 
-The main `RuboCop` gem uses [legacy AST output from parser](https://github.com/whitequark/parser/#usage).
-This gem is meant to be compatible with all settings. For example, to have `-> { ... }` emitted
+This gem, by default, uses most [legacy AST output from parser](https://github.com/whitequark/parser/#usage), except for `emit_forward_arg` which is set to `true`.
+
+The main `RuboCop` gem uses these defaults (and is currently only compatible with these), but this gem can be used separately from `RuboCop` and is meant to be compatible with all settings. For example, to have `-> { ... }` emitted
 as `LambdaNode` instead of `SendNode`:
 
 ```ruby
diff --git a/lib/rubocop/ast/builder.rb b/lib/rubocop/ast/builder.rb
index f360d8731..9ef6f8c9f 100644
--- a/lib/rubocop/ast/builder.rb
+++ b/lib/rubocop/ast/builder.rb
@@ -14,6 +14,8 @@ module AST
     #   parser = Parser::Ruby25.new(builder)
     #   root_node = parser.parse(buffer)
     class Builder < Parser::Builders::Default
+      self.emit_forward_arg = true
+
       NODE_MAP = {
         and:          AndNode,
         alias:        AliasNode,
diff --git a/rubocop-ast.gemspec b/rubocop-ast.gemspec
index 8f683c5d2..d0d84e852 100644
--- a/rubocop-ast.gemspec
+++ b/rubocop-ast.gemspec
@@ -29,7 +29,7 @@ Gem::Specification.new do |s|
     'bug_tracker_uri' => 'https://github.com/rubocop-hq/rubocop-ast/issues'
   }
 
-  s.add_runtime_dependency('parser', '>= 2.7.0.1')
+  s.add_runtime_dependency('parser', '>= 2.7.1.4')
 
   s.add_development_dependency('bundler', '>= 1.15.0', '< 3.0')
 
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 919b63dc3..020a6140f 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -8,7 +8,10 @@
 end
 
 require 'rubocop-ast'
-RuboCop::AST::Builder.modernize if ENV['MODERNIZE']
+if ENV['MODERNIZE']
+  RuboCop::AST::Builder.modernize
+  RuboCop::AST::Builder.emit_forward_arg = false # inverse of default
+end
 
 RSpec.shared_context 'ruby 2.3', :ruby23 do
   let(:ruby_version) { 2.3 }