[Fix #9025] Add AllowedMethods to Lint/ConstantDefinitionInBlock

Fixes #9025.

This PR adds `AllowedMethods` option to `Lint/ConstantDefinitionInBlock`.

The following example can be allowed by configuring `AllowedMethods`.

```ruby
class TestEnum < T::Enum
  enums do
    Foo = new("foo")
  end
end
```

Example configuration:

```yaml
# .rubocop.yml
Lint/ConstantDefinitionInBlock:
  AllowedMethods:
    - enums
```

changelog/new_add_allow_methods_to_constant_definition_in_block.md

@@ -0,0 +1 @@
+* [#9025](https://github.com/rubocop-hq/rubocop/issues/9025): Add `AllowedMethods` option to `Lint/ConstantDefinitionInBlock`. ([@koic][])

config/default.yml

@@ -1400,6 +1400,8 @@ Lint/ConstantDefinitionInBlock:
   StyleGuide: '#no-constant-definition-in-block'
   Enabled: true
   VersionAdded: '0.91'
+  VersionChanged: '1.3'
+  AllowedMethods: []
 
 Lint/ConstantResolution:
   Description: 'Check that constants are fully qualified with `::`.'

docs/modules/ROOT/pages/cops_lint.adoc

@@ -361,7 +361,7 @@ end
 | Yes
 | No
 | 0.91
-| -
+| 1.3
 |===
 
 Do not define constants within a block, since the block's scope does not
@@ -415,6 +415,28 @@ module M
 end
 ----
 
+==== AllowedMethods: ['enums']
+
+[source,ruby]
+----
+# good
+class TestEnum < T::Enum
+  enums do
+    Foo = new("foo")
+  end
+end
+----
+
+=== Configurable attributes
+
+|===
+| Name | Default value | Configurable values
+
+| AllowedMethods
+| `[]`
+| Array
+|===
+
 === References
 
 * https://rubystyle.guide#no-constant-definition-in-block

lib/rubocop/cop/lint/constant_definition_in_block.rb

@@ -49,7 +49,18 @@ module Lint
       #       const_set(:LIST, [])
       #     end
       #   end
+      #
+      # @example AllowedMethods: ['enums']
+      #   # good
+      #   class TestEnum < T::Enum
+      #     enums do
+      #       Foo = new("foo")
+      #     end
+      #   end
+      #
       class ConstantDefinitionInBlock < Base
+        include AllowedMethods
+
         MSG = 'Do not define constants this way within a block.'
 
         def_node_matcher :constant_assigned_in_block?, <<~PATTERN
@@ -61,13 +72,23 @@ class ConstantDefinitionInBlock < Base
         PATTERN
 
         def on_casgn(node)
-          add_offense(node) if constant_assigned_in_block?(node)
+          return if !constant_assigned_in_block?(node) || allowed_method?(method_name(node))
+
+          add_offense(node)
         end
 
         def on_class(node)
-          add_offense(node) if module_defined_in_block?(node)
+          return if !module_defined_in_block?(node) || allowed_method?(method_name(node))
+
+          add_offense(node)
         end
         alias on_module on_class
+
+        private
+
+        def method_name(node)
+          node.ancestors.find(&:block_type?).send_node.method_name
+        end
       end
     end
   end

spec/rubocop/cop/lint/constant_definition_in_block_spec.rb

@@ -1,10 +1,8 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Lint::ConstantDefinitionInBlock do
+RSpec.describe RuboCop::Cop::Lint::ConstantDefinitionInBlock, :config do
   subject(:cop) { described_class.new(config) }
 
-  let(:config) { RuboCop::Config.new }
-
   it 'does not register an offense for a top-level constant' do
     expect_no_offenses(<<~RUBY)
       FOO = 1
@@ -134,4 +132,71 @@ module Foo; end
       end
     RUBY
   end
+
+  context 'when `AllowedMethods: [enums]`' do
+    let(:cop_config) { { 'AllowedMethods' => ['enums'] } }
+
+    it 'does not register an offense for a casign used within a block of `enums` method' do
+      expect_no_offenses(<<~RUBY)
+        class TestEnum < T::Enum
+          enums do
+            Foo = new("foo")
+          end
+        end
+      RUBY
+    end
+
+    it 'does not register an offense for a class defined within a block of `enums` method' do
+      expect_no_offenses(<<~RUBY)
+        enums do
+          class Foo
+          end
+        end
+      RUBY
+    end
+
+    it 'does not register an offense for a module defined within a block of `enums` method' do
+      expect_no_offenses(<<~RUBY)
+        enums do
+          module Foo
+          end
+        end
+      RUBY
+    end
+  end
+
+  context 'when `AllowedMethods: []`' do
+    let(:cop_config) { { 'AllowedMethods' => [] } }
+
+    it 'registers an offense for a casign used within a block of `enums` method' do
+      expect_offense(<<~RUBY)
+        class TestEnum < T::Enum
+          enums do
+            Foo = new("foo")
+            ^^^^^^^^^^^^^^^^ Do not define constants this way within a block.
+          end
+        end
+      RUBY
+    end
+
+    it 'registers an offense for a class defined within a block of `enums` method' do
+      expect_offense(<<~RUBY)
+        enums do
+          class Foo
+          ^^^^^^^^^ Do not define constants this way within a block.
+          end
+        end
+      RUBY
+    end
+
+    it 'registers an offense for a module defined within a block of `enums` method' do
+      expect_offense(<<~RUBY)
+        enums do
+          module Foo
+          ^^^^^^^^^^ Do not define constants this way within a block.
+          end
+        end
+      RUBY
+    end
+  end
 end