[Fix #9771] Fix a false positive for Style/TrivialAccessors

Fixes #9771.

This PR changes `AllowDSLWriters` to true by default because
it's still a trivial accessor and most people are unlikely to be
creating DSLs.

By this will prevent a false positive for `Style/TrivialAccessors`
when defining a method that is not a DSL writer.

changelog/fix_false_positive_for_style_trivial_accessors.md

@@ -0,0 +1 @@
+* [#9771](https://github.com/rubocop/rubocop/issues/9771): Change `AllowDSLWriters` to true by default for `Style/TrivialAccessors`. ([@koic][])

config/default.yml

@@ -4745,7 +4745,7 @@ Style/TrivialAccessors:
   StyleGuide: '#attr_family'
   Enabled: true
   VersionAdded: '0.9'
-  VersionChanged: '0.77'
+  VersionChanged: '<<next>>'
   # When set to `false` the cop will suggest the use of accessor methods
   # in situations like:
   #
@@ -4764,7 +4764,7 @@ Style/TrivialAccessors:
   # on_exception :restart
   #
   # Commonly used in DSLs
-  AllowDSLWriters: false
+  AllowDSLWriters: true
   IgnoreClassMethods: false
   AllowedMethods:
     - to_ary

lib/rubocop/cop/style/trivial_accessors.rb

@@ -27,6 +27,71 @@ module Style
       #   class << self
       #     attr_reader :baz
       #   end
+      #
+      # @example ExactNameMatch: true (default)
+      #   # good
+      #   def name
+      #     @other_name
+      #   end
+      #
+      # @example ExactNameMatch: false
+      #   # bad
+      #   def name
+      #     @other_name
+      #   end
+      #
+      # @example AllowPredicates: true (default)
+      #   # good
+      #   def foo?
+      #     @foo
+      #   end
+      #
+      # @example AllowPredicates: false
+      #   # bad
+      #   def foo?
+      #     @foo
+      #   end
+      #
+      #   # good
+      #   attr_reader :foo
+      #
+      # @example AllowDSLWriters: true (default)
+      #   # good
+      #   def on_exception(action)
+      #     @on_exception=action
+      #   end
+      #
+      # @example AllowDSLWriters: false
+      #   # bad
+      #   def on_exception(action)
+      #     @on_exception=action
+      #   end
+      #
+      #   # good
+      #   attr_writer :on_exception
+      #
+      # @example IgnoreClassMethods: false (default)
+      #   # bad
+      #   def self.foo
+      #     @foo
+      #   end
+      #
+      #   # good
+      #   class << self
+      #     attr_reader :foo
+      #   end
+      #
+      # @example IgnoreClassMethods: true
+      #   # good
+      #   def self.foo
+      #     @foo
+      #   end
+      #
+      # @exampole AllowedMethods: ['allowed_method']
+      #   # good
+      #   def allowed_method
+      #     @foo
+      #   end
       class TrivialAccessors < Base
         include AllowedMethods
         extend AutoCorrector

spec/rubocop/cop/style/trivial_accessors_spec.rb

@@ -59,14 +59,20 @@ class << self
   it 'registers an offense on class writer' do
     expect_offense(<<~RUBY)
       class Foo
-        def self.foo(val)
+        def self.foo=(val)
         ^^^ Use `attr_writer` to define trivial writer methods.
           @foo = val
         end
       end
     RUBY
 
-    expect_no_corrections
+    expect_correction(<<~RUBY)
+      class Foo
+        class << self
+          attr_writer :foo
+        end
+      end
+    RUBY
   end
 
   it 'registers an offense on reader with braces' do
@@ -121,25 +127,26 @@ class Foo
   it 'registers an offense on one-liner writer' do
     expect_offense(<<~RUBY)
       class Foo
-        def foo(val); @foo=val; end
+        def foo=(val); @foo=val; end
         ^^^ Use `attr_writer` to define trivial writer methods.
       end
     RUBY
 
-    expect_no_corrections
+    expect_correction(<<~RUBY)
+      class Foo
+        attr_writer :foo
+      end
+    RUBY
   end
 
-  it 'registers an offense on DSL-style trivial writer' do
-    expect_offense(<<~RUBY)
+  it 'does not register an offense on DSL-style writer' do
+    expect_no_offenses(<<~RUBY)
       class Foo
         def foo(val)
-        ^^^ Use `attr_writer` to define trivial writer methods.
           @foo = val
         end
       end
     RUBY
-
-    expect_no_corrections
   end
 
   it 'registers an offense on reader with `private`' do
@@ -353,7 +360,7 @@ class << @blah
     it 'registers an offense when names mismatch in writer' do
       expect_offense(<<~RUBY)
         class Foo
-          def foo(val)
+          def foo=(val)
           ^^^ Use `attr_writer` to define trivial writer methods.
             @f = val
           end
@@ -446,17 +453,20 @@ def foo?
     end
   end
 
-  context 'with DSL allowed' do
-    let(:cop_config) { { 'AllowDSLWriters' => true } }
+  context 'with DSL denied' do
+    let(:cop_config) { { 'AllowDSLWriters' => false } }
 
-    it 'accepts DSL-style writer' do
-      expect_no_offenses(<<~RUBY)
+    it 'registers an offense on DSL-style writer' do
+      expect_offense(<<~RUBY)
         class Foo
           def foo(val)
+          ^^^ Use `attr_writer` to define trivial writer methods.
             @foo = val
           end
         end
       RUBY
+
+      expect_no_corrections
     end
   end