[Fixes #43] Basic support for non-legacy emitters

README.md

@@ -30,6 +30,16 @@ gem 'rubocop-ast'
 
 Refer to the documentation of `RuboCop::AST::Node` and [`RuboCop::AST::NodePattern`](docs/modules/ROOT/pages/node_pattern.adoc)
 
+### 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
+as `LambdaNode` instead of `SendNode`:
+
+```ruby
+RuboCop::AST::Builder.emit_lambda = true
+```
+
 ## Contributing
 
 Checkout the [contribution guidelines](CONTRIBUTING.md).

lib/rubocop/ast.rb

@@ -35,8 +35,11 @@
 require_relative 'ast/node/float_node'
 require_relative 'ast/node/hash_node'
 require_relative 'ast/node/if_node'
+require_relative 'ast/node/index_node'
+require_relative 'ast/node/indexasgn_node'
 require_relative 'ast/node/int_node'
 require_relative 'ast/node/keyword_splat_node'
+require_relative 'ast/node/lambda_node'
 require_relative 'ast/node/module_node'
 require_relative 'ast/node/or_node'
 require_relative 'ast/node/pair_node'

lib/rubocop/ast/builder.rb

@@ -35,9 +35,12 @@ class Builder < Parser::Builders::Default
         hash:         HashNode,
         if:           IfNode,
         int:          IntNode,
+        index:        IndexNode,
+        indexasgn:    IndexasgnNode,
         irange:       RangeNode,
         erange:       RangeNode,
         kwsplat:      KeywordSplatNode,
+        lambda:       LambdaNode,
         module:       ModuleNode,
         or:           OrNode,
         pair:         PairNode,

lib/rubocop/ast/node/def_node.rb

@@ -24,7 +24,7 @@ def void_context?
       #
       # @return [Boolean] whether the `def` node uses argument forwarding
       def argument_forwarding?
-        arguments.any?(&:forward_args_type?)
+        arguments.any?(&:forward_args_type?) || arguments.any?(&:forward_arg_type?)
       end
 
       # The name of the defined method as a symbol.

lib/rubocop/ast/node/forward_args_node.rb

@@ -5,6 +5,21 @@ module AST
     # A node extension for `forward-args` nodes. This will be used in place
     # of a plain node when the builder constructs the AST, making its methods
     # available to all `forward-args` nodes within RuboCop.
+    #
+    # Not used with modern emitters:
+    #
+    #   $ ruby-parse -e "def foo(...); end"
+    #   (def :foo
+    #     (args
+    #       (forward-arg)) nil)
+    #   $ ruby-parse --legacy -e "->(foo) { bar }"
+    #   (def :foo
+    #     (forward-args) nil)
+    #
+    # Note the extra 's' with legacy form.
+    #
+    # The main RuboCop runs in legacy mode; this node is only used
+    # if user `AST::Builder.modernize` or `AST::Builder.emit_lambda=true`
     class ForwardArgsNode < Node
       include CollectionNode
 

lib/rubocop/ast/node/index_node.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module AST
+    # Used for modern support only!
+    # Not as thoroughly tested as legacy equivalent
+    #
+    #   $ ruby-parse -e "foo[:bar]"
+    #   (index
+    #     (send nil :foo)
+    #     (sym :bar))
+    #   $ ruby-parse --legacy -e "foo[:bar]"
+    #   (send
+    #     (send nil :foo) :[]
+    #     (sym :bar))
+    #
+    # The main RuboCop runs in legacy mode; this node is only used
+    # if user `AST::Builder.modernize` or `AST::Builder.emit_index=true`
+    class IndexNode < Node
+      include ParameterizedNode
+      include MethodDispatchNode
+
+      # For similarity with legacy mode
+      def attribute_accessor?
+        false
+      end
+
+      # For similarity with legacy mode
+      def assignment_method?
+        false
+      end
+
+      # For similarity with legacy mode
+      def method_name
+        :[]
+      end
+
+      # An array containing the arguments of the dispatched method.
+      #
+      # @return [Array<Node>] the arguments of the dispatched method
+      def arguments
+        node_parts[1..-1]
+      end
+    end
+  end
+end

lib/rubocop/ast/node/indexasgn_node.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module AST
+    # Used for modern support only!
+    # Not as thoroughly tested as legacy equivalent
+    #
+    #   $ ruby-parse -e "foo[:bar] = :baz"
+    #   (indexasgn
+    #     (send nil :foo)
+    #     (sym :bar)
+    #     (sym :baz))
+    #   $ ruby-parse --legacy -e "foo[:bar] = :baz"
+    #   (send
+    #     (send nil :foo) :[]=
+    #     (sym :bar)
+    #     (sym :baz))
+    #
+    # The main RuboCop runs in legacy mode; this node is only used
+    # if user `AST::Builder.modernize` or `AST::Builder.emit_index=true`
+    class IndexasgnNode < Node
+      include ParameterizedNode
+      include MethodDispatchNode
+
+      # For similarity with legacy mode
+      def attribute_accessor?
+        false
+      end
+
+      # For similarity with legacy mode
+      def assignment_method?
+        true
+      end
+
+      # For similarity with legacy mode
+      def method_name
+        :[]=
+      end
+
+      # An array containing the arguments of the dispatched method.
+      #
+      # @return [Array<Node>] the arguments of the dispatched method
+      def arguments
+        node_parts[1..-1]
+      end
+    end
+  end
+end

lib/rubocop/ast/node/lambda_node.rb

@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module AST
+    # Used for modern support only:
+    # Not as thoroughly tested as legacy equivalent
+    #
+    #   $ ruby-parse -e "->(foo) { bar }"
+    #   (block
+    #     (lambda)
+    #     (args
+    #       (arg :foo))
+    #     (send nil :bar))
+    #   $ ruby-parse --legacy -e "->(foo) { bar }"
+    #   (block
+    #     (send nil :lambda)
+    #     (args
+    #       (arg :foo))
+    #     (send nil :bar))
+    #
+    # The main RuboCop runs in legacy mode; this node is only used
+    # if user `AST::Builder.modernize` or `AST::Builder.emit_lambda=true`
+    class LambdaNode < Node
+      include ParameterizedNode
+      include MethodDispatchNode
+
+      # For similarity with legacy mode
+      def lambda?
+        true
+      end
+
+      # For similarity with legacy mode
+      def lambda_literal?
+        true
+      end
+
+      # For similarity with legacy mode
+      def attribute_accessor?
+        false
+      end
+
+      # For similarity with legacy mode
+      def assignment_method?
+        false
+      end
+
+      # For similarity with legacy mode
+      def method_name
+        :lambda
+      end
+
+      # For similarity with legacy mode
+      def arguments
+        []
+      end
+    end
+  end
+end

lib/rubocop/ast/node/mixin/method_dispatch_node.rb

@@ -3,7 +3,8 @@
 module RuboCop
   module AST
     # Common functionality for nodes that are a kind of method dispatch:
-    # `send`, `csend`, `super`, `zsuper`, `yield`, `defined?`
+    # `send`, `csend`, `super`, `zsuper`, `yield`, `defined?`,
+    # and (modern only): `index`, `indexasgn`, `lambda`
     module MethodDispatchNode
       extend NodePattern::Macros
       include MethodIdentifierPredicates

lib/rubocop/ast/node/mixin/parameterized_node.rb

@@ -4,6 +4,7 @@ module RuboCop
   module AST
     # Common functionality for nodes that are parameterized:
     # `send`, `super`, `zsuper`, `def`, `defs`
+    # and (modern only): `index`, `indexasgn`, `lambda`
     module ParameterizedNode
       # Checks whether this node's arguments are wrapped in parentheses.
       #

lib/rubocop/ast/traversal.rb

@@ -19,9 +19,10 @@ def walk(node)
                              rational str sym regopt self lvar
                              ivar cvar gvar nth_ref back_ref cbase
                              arg restarg blockarg shadowarg
-                             kwrestarg zsuper lambda redo retry
+                             kwrestarg zsuper redo retry
                              forward_args forwarded_args
-                             match_var match_nil_pattern empty_else].freeze
+                             match_var match_nil_pattern empty_else
+                             forward_arg lambda procarg0 __ENCODING__].freeze
       ONE_CHILD_NODE    = %i[splat kwsplat block_pass not break next
                              preexe postexe match_current_line defined?
                              arg_expr pin match_rest if_guard unless_guard
@@ -33,7 +34,8 @@ def walk(node)
                              match_with_lvasgn begin kwbegin return
                              in_match match_alt
                              match_as array_pattern array_pattern_with_tail
-                             hash_pattern const_pattern].freeze
+                             hash_pattern const_pattern
+                             index indexasgn].freeze
       SECOND_CHILD_ONLY = %i[lvasgn ivasgn cvasgn gvasgn optarg kwarg
                              kwoptarg].freeze
 

spec/rubocop/ast/forward_args_node_spec.rb

@@ -2,18 +2,21 @@
 
 RSpec.describe RuboCop::AST::ForwardArgsNode do
   let(:args_node) { parse_source(source).ast.arguments }
+  let(:source) { 'def foo(...); end' }
 
   context 'when using Ruby 2.7 or newer', :ruby27 do
-    describe '.new' do
-      let(:source) { 'def foo(...); end' }
+    if RuboCop::AST::Builder.emit_forward_arg
+      describe '#to_a' do
+        it { expect(args_node.to_a).to contain_exactly(be_forward_arg_type) }
+      end
+    else
+      describe '.new' do
+        it { expect(args_node.is_a?(described_class)).to be(true) }
+      end
 
-      it { expect(args_node.is_a?(described_class)).to be(true) }
-    end
-
-    describe '#to_a' do
-      let(:source) { 'def foo(...); end' }
-
-      it { expect(args_node.to_a).to contain_exactly(args_node) }
+      describe '#to_a' do
+        it { expect(args_node.to_a).to contain_exactly(args_node) }
+      end
     end
   end
 end

spec/spec_helper.rb

@@ -8,6 +8,7 @@
 end
 
 require 'rubocop-ast'
+RuboCop::AST::Builder.modernize if ENV['MODERNIZE']
 
 RSpec.shared_context 'ruby 2.3', :ruby23 do
   let(:ruby_version) { 2.3 }