From 792b29d84be67a0ac162e5859676c28f3426a476 Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Tue, 25 May 2021 00:01:59 +0900
Subject: [PATCH] [Fix #9819] Fix a false negative for
 `Style/TopLevelMethodDefinition`

Fixes #9819.

This PR fixes a false negative for `Style/TopLevelMethodDefinition`
when defining a top-level method after a class definition.
---
 ...negative_for_style_top_level_method_definition.md |  1 +
 lib/rubocop/cop/style/top_level_method_definition.rb | 12 ++++++++++--
 .../cop/style/top_level_method_definition_spec.rb    | 10 ++++++++++
 3 files changed, 21 insertions(+), 2 deletions(-)
 create mode 100644 changelog/fix_false_negative_for_style_top_level_method_definition.md

diff --git a/changelog/fix_false_negative_for_style_top_level_method_definition.md b/changelog/fix_false_negative_for_style_top_level_method_definition.md
new file mode 100644
index 00000000000..b064e29b540
--- /dev/null
+++ b/changelog/fix_false_negative_for_style_top_level_method_definition.md
@@ -0,0 +1 @@
+* [#9819](https://github.com/rubocop/rubocop/issues/9819): Fix a false negative for `Style/TopLevelMethodDefinition` when defining a top-level method after a class definition. ([@koic][])
diff --git a/lib/rubocop/cop/style/top_level_method_definition.rb b/lib/rubocop/cop/style/top_level_method_definition.rb
index d868dbf2780..4b94428b2ae 100644
--- a/lib/rubocop/cop/style/top_level_method_definition.rb
+++ b/lib/rubocop/cop/style/top_level_method_definition.rb
@@ -50,7 +50,7 @@ class TopLevelMethodDefinition < Base
         RESTRICT_ON_SEND = %i[define_method].freeze
 
         def on_def(node)
-          return unless node.root?
+          return unless top_level_method_definition?(node)
 
           add_offense(node)
         end
@@ -58,13 +58,21 @@ def on_def(node)
         alias on_send on_def
 
         def on_block(node)
-          return unless define_method_block?(node) && node.root?
+          return unless define_method_block?(node) && top_level_method_definition?(node)
 
           add_offense(node)
         end
 
         private
 
+        def top_level_method_definition?(node)
+          if node.parent&.begin_type?
+            node.parent.root?
+          else
+            node.root?
+          end
+        end
+
         # @!method define_method_block?(node)
         def_node_matcher :define_method_block?, <<~PATTERN
           (block (send _ {:define_method} _) ...)
diff --git a/spec/rubocop/cop/style/top_level_method_definition_spec.rb b/spec/rubocop/cop/style/top_level_method_definition_spec.rb
index 3d08bb58596..e310f943964 100644
--- a/spec/rubocop/cop/style/top_level_method_definition_spec.rb
+++ b/spec/rubocop/cop/style/top_level_method_definition_spec.rb
@@ -40,6 +40,16 @@ def self.foo; end
     end
   end
 
+  it 'registers an offense when defining a top-level method after a class definition' do
+    expect_offense(<<~RUBY)
+      class Foo
+      end
+
+      def foo; end
+      ^^^^^^^^^^^^ Do not define methods at the top-level.
+    RUBY
+  end
+
   it 'does not register an offense when using module' do
     expect_no_offenses(<<~RUBY)
       module Foo