Improve parent_module_name (#177)

* Fix unexpected non-local exits on Rubocop::AST::Node#parent_module_name

With this PR, when Rubocop::AST::Node#parent_module_name_part is executed, it will no longer do non-local exits when a block is evaluated, and evaluating singleton_class or block in Rubocop::AST::Node#parent_module_name will behave as expected.
With this change, this PR aims to resolve the following issue.

rubocop/rubocop#5022

Co-authored-by: masatoshi_moritsuka <yakiyaki_ikayaki@yahoo.co.jp>

changelog/fix_fix_unexpected_nonlocal_exits_on_rubocop_ast_node_parent_module_name.md

@@ -0,0 +1 @@
+* [#176](https://github.com/rubocop-hq/rubocop-ast/pull/176): Fix unexpected non-local exits on  Rubocop::AST::Node#parent_module_name. ([@sanfrecce-osaka][])

lib/rubocop/ast/node.rb

@@ -612,19 +612,17 @@ def while_until_value_used?
       def parent_module_name_part(node)
         case node.type
         when :class, :module, :casgn
-          # TODO: if constant name has cbase (leading ::), then we don't need
-          # to keep traversing up through nested classes/modules
+          # TODO: if constant name has cbase (leading ::), then we must not
+          # keep traversing up through nested classes/modules
           node.defined_module_name
         when :sclass
-          yield parent_module_name_for_sclass(node)
+          parent_module_name_for_sclass(node)
         else # block
           parent_module_name_for_block(node) { yield nil }
         end
       end
 
       def parent_module_name_for_sclass(sclass_node)
-        # TODO: look for constant definition and see if it is nested
-        # inside a class or module
         subject = sclass_node.children[0]
 
         if subject.const_type?

spec/rubocop/ast/node_pattern_spec.rb

@@ -10,7 +10,6 @@ def parse(code)
     builder = RuboCop::AST::Builder.new
     Parser::CurrentRuby.new(builder).parse(buffer)
   end
-
   let(:root_node) { parse(ruby) }
   let(:node) { root_node }
   let(:params) { [] }

spec/rubocop/ast/node_spec.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 RSpec.describe RuboCop::AST::Node do
-  let(:ast) { RuboCop::AST::ProcessedSource.new(src, ruby_version).ast }
+  let(:ast) { parse_source(src).node }
   let(:node) { ast }
 
   describe '#value_used?' do
@@ -659,4 +659,71 @@ def variables; end
       end
     end
   end
+
+  describe '#parent_module_name' do
+    subject(:parent_module_name) { node.parent_module_name }
+    context 'when node on top level' do
+      let(:src) { 'def config; end' }
+
+      it { is_expected.to eq 'Object' }
+    end
+
+    context 'when node on module' do
+      let(:src) do
+        <<~RUBY
+          module Foo
+            >>attr_reader :config<<
+          end
+        RUBY
+      end
+
+      it { is_expected.to eq 'Foo' }
+    end
+
+    context 'when node on singleton class' do
+      let(:src) do
+        <<~RUBY
+          module Foo
+            class << self
+              >>attr_reader :config<<
+            end
+          end
+        RUBY
+      end
+
+      it { is_expected.to eq 'Foo::#<Class:Foo>' }
+    end
+
+    context 'when node on class in singleton class' do
+      let(:src) do
+        <<~RUBY
+          module Foo
+            class << self
+              class Bar
+                >>attr_reader :config<<
+              end
+            end
+          end
+        RUBY
+      end
+
+      it { is_expected.to eq 'Foo::#<Class:Foo>::Bar' }
+    end
+
+    context 'when node nested in an unknown block' do
+      let(:src) do
+        <<~RUBY
+          module Foo
+            foo do
+              class Bar
+                >>attr_reader :config<<
+              end
+            end
+          end
+        RUBY
+      end
+
+      it { is_expected.to eq nil }
+    end
+  end
 end