Add VarNode class for lvar, ivar, cvar and gvar node types

changelog/new_add_varnode_class_for_lvar_ivar_cvar_and.md

@@ -0,0 +1 @@
+* [#204](https://github.com/rubocop-hq/rubocop-ast/pull/204): Add `VarNode` class for `lvar`, `ivar`, `cvar` and `gvar` node types. ([@dvandersluis][])

docs/modules/ROOT/pages/node_types.adoc

@@ -88,7 +88,7 @@ The following fields are given when relevant to nodes in the source code:
 
 |csend|Null-safe method invocation, i.e. using `&.`|First child is the receiver node (e.g. `self`), second child is the method name (e.g. `:foo=`) and the remaining children (if any) are nodes representing arguments.|foo&.bar|https://rubydoc.info/github/rubocop/rubocop-ast/RuboCop/AST/SendNode[SendNode]
 
-|cvar|Class variable access|One child, the variable name `:@@cfoo`|@@cfoo|N/A
+|cvar|Class variable access|One child, the variable name `:@@cfoo`|@@cfoo|https://rubydoc.info/github/rubocop/rubocop-ast/RuboCop/AST/VarNode[VarNode]
 
 |cvasgn|Class variable assignment|Two children: the variable name `:@@foo` and the expression being assigned|@@foo = 5|https://rubydoc.info/github/rubocop/rubocop-ast/RuboCop/AST/AsgnNode[AsgnNode]
 
@@ -120,7 +120,7 @@ The following fields are given when relevant to nodes in the source code:
 
 |forwarded-args|Forwarding arguments into a method call|None|foo(...)|N/A
 
-|gvar|Global variable access|One child, the variable name as a symbol `:$foo`|$foo|N/A
+|gvar|Global variable access|One child, the variable name as a symbol `:$foo`|$foo|https://rubydoc.info/github/rubocop/rubocop-ast/RuboCop/AST/VarNode[VarNode]
 
 |gvasgn|Global variable assignment|Two children, the variable name `:$foo` and the expression being assigned|$foo = 5|https://rubydoc.info/github/rubocop/rubocop-ast/RuboCop/AST/AsgnNode[AsgnNode]
 
@@ -130,7 +130,7 @@ The following fields are given when relevant to nodes in the source code:
 
 |int|Integer literal|1, the integer value|-123|https://rubydoc.info/github/rubocop/rubocop-ast/RuboCop/AST/IntNode[IntNode]
 
-|ivar|Instance variable access|One child, the variable name `:@foo`|@foo|N/A
+|ivar|Instance variable access|One child, the variable name `:@foo`|@foo|https://rubydoc.info/github/rubocop/rubocop-ast/RuboCop/AST/VarNode[VarNode]
 
 |ivasgn|Instance variable assignment|Two children, the variable name `:@foo` and the expression being assigned|@foo = 5|https://rubydoc.info/github/rubocop/rubocop-ast/RuboCop/AST/AsgnNode[AsgnNode]
 
@@ -148,7 +148,7 @@ The following fields are given when relevant to nodes in the source code:
 
 |kwrestargs|Double splat used for keyword arguments inside a function definition (as opposed to a function call). Must come inside an `args`.|One child - a symbol, representing the argument name, if a name is given. If no name given, it has no children..|def foo(**kwargs)|https://rubydoc.info/github/rubocop/rubocop-ast/RuboCop/AST/ArgNode[ArgNode]
 
-|lvar|Local variable access|One child, the variable name|foo|N/A
+|lvar|Local variable access|One child, the variable name|foo|https://rubydoc.info/github/rubocop/rubocop-ast/RuboCop/AST/VarNode[VarNode]
 
 |lvasgn|Local variable assignment|Two children: The variable name (symbol) and the expression.|a = some_thing|https://rubydoc.info/github/rubocop/rubocop-ast/RuboCop/AST/AsgnNode[AsgnNode]
 

lib/rubocop/ast.rb

@@ -81,6 +81,7 @@
 require_relative 'ast/node/super_node'
 require_relative 'ast/node/symbol_node'
 require_relative 'ast/node/until_node'
+require_relative 'ast/node/var_node'
 require_relative 'ast/node/when_node'
 require_relative 'ast/node/while_node'
 require_relative 'ast/node/yield_node'

lib/rubocop/ast/builder.rb

@@ -85,6 +85,10 @@ class Builder < Parser::Builders::Default
         sym:          SymbolNode,
         until:        UntilNode,
         until_post:   UntilNode,
+        lvar:         VarNode,
+        ivar:         VarNode,
+        cvar:         VarNode,
+        gvar:         VarNode,
         when:         WhenNode,
         while:        WhileNode,
         while_post:   WhileNode,

lib/rubocop/ast/node/casgn_node.rb

@@ -19,6 +19,7 @@ def namespace
       def name
         node_parts[1]
       end
+      alias short_name name
 
       # The expression being assigned to the variable.
       #

lib/rubocop/ast/node/var_node.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module AST
+    # A node extension for `lvar`, `ivar`, `cvar` and `gvar` nodes.
+    # This will be used in place of a plain node when the builder constructs
+    # the AST, making its methods available to all assignment nodes within RuboCop.
+    class VarNode < Node
+      # @return [Symbol] The name of the variable.
+      def name
+        node_parts[0]
+      end
+    end
+  end
+end

spec/rubocop/ast/var_node_spec.rb

@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::AST::VarNode do
+  let(:node) { parse_source(source).node }
+
+  describe '.new' do
+    context 'with a `lvar` node' do
+      let(:source) { 'x = 1; >>x<<' }
+
+      it { expect(node).to be_a(described_class) }
+    end
+
+    context 'with an `ivar` node' do
+      let(:source) { '@x' }
+
+      it { expect(node).to be_a(described_class) }
+    end
+
+    context 'with an `cvar` node' do
+      let(:source) { '@@x' }
+
+      it { expect(node).to be_a(described_class) }
+    end
+
+    context 'with an `gvar` node' do
+      let(:source) { '$x' }
+
+      it { expect(node).to be_a(described_class) }
+    end
+  end
+
+  describe '#name' do
+    subject { node.name }
+
+    context 'with a `lvar` node' do
+      let(:source) { 'x = 1; >>x<<' }
+
+      it { is_expected.to eq(:x) }
+    end
+
+    context 'with an `ivar` node' do
+      let(:source) { '@x' }
+
+      it { is_expected.to eq(:@x) }
+    end
+
+    context 'with an `cvar` node' do
+      let(:source) { '@@x' }
+
+      it { is_expected.to eq(:@@x) }
+    end
+
+    context 'with an `gvar` node' do
+      let(:source) { '$x' }
+
+      it { is_expected.to eq(:$x) }
+    end
+  end
+end