LeakyConstantDeclaration - allow definitions in explicit namespaces

Constant, classes, and modules that are defined on explicit namespaces
do not "leak" into the global namespace, because the author is making
their intention clear. This is even true when when explicitly using
`::`. While doing this may not be a particularly good practice, it
should ideally not result in an offense.

The practice is described here: https://makandracards.com/makandra/47189-rspec-how-to-define-classes-for-specs#section-1-defining-the-constant-on-the-example-class

Author: naveg

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Master (Unreleased)
 
+- Fix a false positive for `RSpec/LeakyConstantDeclaration` when defining constants in explicit namespaces. ([@naveg])
+
 ## 3.6.0 (2025-04-18)
 
 - Fix false positive in `RSpec/Pending`, where it would mark the default block `it` as an offense. ([@bquorning])

lib/rubocop/cop/rspec/leaky_constant_declaration.rb

@@ -100,18 +100,21 @@ class LeakyConstantDeclaration < Base
 
         def on_casgn(node)
           return unless inside_describe_block?(node)
+          return if defined_on_explicit_namespace?(node)
 
           add_offense(node, message: MSG_CONST)
         end
 
         def on_class(node)
           return unless inside_describe_block?(node)
+          return if defined_on_explicit_namespace?(node)
 
           add_offense(node, message: MSG_CLASS)
         end
 
         def on_module(node)
           return unless inside_describe_block?(node)
+          return if defined_on_explicit_namespace?(node)
 
           add_offense(node, message: MSG_MODULE)
         end
@@ -121,6 +124,16 @@ def on_module(node)
         def inside_describe_block?(node)
           node.each_ancestor(:block).any? { |ancestor| spec_group?(ancestor) }
         end
+
+        def defined_on_explicit_namespace?(node)
+          if node.is_a?(RuboCop::AST::ClassNode) ||
+              node.is_a?(RuboCop::AST::ModuleNode)
+
+            node.loc.name.source.include?('::')
+          elsif node.is_a?(RuboCop::AST::CasgnNode)
+            node.namespace&.cbase_type? || node.const_name.include?('::')
+          end
+        end
       end
     end
   end

spec/rubocop/cop/rspec/leaky_constant_declaration_spec.rb

@@ -31,6 +31,30 @@
       RUBY
     end
 
+    it 'ignores constant defined on the example group' do
+      expect_no_offenses(<<~RUBY)
+        describe SomeClass do
+          self::CONSTANT = "Accessible as self.class::CONSTANT".freeze
+        end
+      RUBY
+    end
+
+    it 'ignores constant defined in an explicit namespace' do
+      expect_no_offenses(<<~RUBY)
+        describe SomeClass do
+          Foo::CONSTANT = "Accessible as Foo::CONSTANT".freeze
+        end
+      RUBY
+    end
+
+    it 'ignores classes defined explicitly in the global namespace' do
+      expect_no_offenses(<<~RUBY)
+        describe SomeClass do
+          ::CONSTANT = "Accessible as ::CONSTANT".freeze
+        end
+      RUBY
+    end
+
     it 'ignores outside of example/shared group' do
       expect_no_offenses(<<~RUBY)
         factory :some_class do
@@ -60,15 +84,32 @@ def method
               end
             end
           end
-         end
+        end
       RUBY
     end
 
-    it 'flags namespaced class' do
-      expect_offense(<<~RUBY)
+    it 'ignores classes defined on the example group' do
+      expect_no_offenses(<<~RUBY)
+        describe SomeClass do
+          class self::DummyClass
+          end
+        end
+      RUBY
+    end
+
+    it 'ignores classes defined in an explicit namespace' do
+      expect_no_offenses(<<~RUBY)
         describe SomeClass do
-          class SomeModule::AnotherModule::DummyClass
-          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Stub class constant instead of declaring explicitly.
+          class Foo::DummyClass
+          end
+        end
+      RUBY
+    end
+
+    it 'ignores classes defined explicitly in the global namespace' do
+      expect_no_offenses(<<~RUBY)
+        describe SomeClass do
+          module ::DummyClass
           end
         end
       RUBY
@@ -93,6 +134,33 @@ module DummyModule
       RUBY
     end
 
+    it 'ignores modules defined on the example group' do
+      expect_no_offenses(<<~RUBY)
+        describe SomeClass do
+          module self::DummyModule
+          end
+        end
+      RUBY
+    end
+
+    it 'ignores modules defined in an explicit namespace' do
+      expect_no_offenses(<<~RUBY)
+        describe SomeClass do
+          module Foo::DummyModule
+          end
+        end
+      RUBY
+    end
+
+    it 'ignores modules defined explicitly in the global namespace' do
+      expect_no_offenses(<<~RUBY)
+        describe SomeClass do
+          module ::DummyModule
+          end
+        end
+      RUBY
+    end
+
     it 'ignores outside of example/shared group' do
       expect_no_offenses(<<~RUBY)
         module Dummymodule