Detect class_variable_set in Style/ClassVars

CHANGELOG.md

@@ -22,6 +22,7 @@
 * [#7868](https://github.com/rubocop-hq/rubocop/pull/7868): **(Breaking)** Extensive refactoring of internal classes `Team`, `Commissioner`, `Corrector`. `Cop::Cop#corrections` not completely compatible. See Upgrade Notes. ([@marcandre][])
 * [#8156](https://github.com/rubocop-hq/rubocop/issues/8156): **(Breaking)** `rubocop -a / --autocorrect` no longer run unsafe corrections; `rubocop -A / --autocorrect-all` run both safe and unsafe corrections. Options `--safe-autocorrect` is deprecated. ([@marcandre][])
 * [#8207](https://github.com/rubocop-hq/rubocop/pull/8207): **(Breaking)** Order for gems names now disregards underscores and dashes unless `ConsiderPunctuation` setting is set to `true`. ([@marcandre][])
+* [#8211](https://github.com/rubocop-hq/rubocop/pull/8211): `Style/ClassVars` cop now detects `class_variable_set`. ([@biinari][])
 
 ## 0.86.0 (2020-06-22)
 

docs/modules/ROOT/pages/cops_style.adoc

@@ -951,6 +951,15 @@ class A
   @@test = 10
 end
 
+class A
+  def self.test(name, value)
+    class_variable_set("@@#{name}", value)
+  end
+end
+
+class A; end
+A.class_variable_set(:@@test, 10)
+
 # good
 class A
   @test = 10
@@ -961,6 +970,12 @@ class A
     @@test # you can access class variable without offense
   end
 end
+
+class A
+  def self.test(name)
+    class_variable_get("@@#{name}") # you can access without offense
+  end
+end
 ----
 
 === References

lib/rubocop/cop/style/class_vars.rb

@@ -19,6 +19,15 @@ module Style
       #     @@test = 10
       #   end
       #
+      #   class A
+      #     def self.test(name, value)
+      #       class_variable_set("@@#{name}", value)
+      #     end
+      #   end
+      #
+      #   class A; end
+      #   A.class_variable_set(:@@test, 10)
+      #
       #   # good
       #   class A
       #     @test = 10
@@ -30,6 +39,12 @@ module Style
       #     end
       #   end
       #
+      #   class A
+      #     def self.test(name)
+      #       class_variable_get("@@#{name}") # you can access without offense
+      #     end
+      #   end
+      #
       class ClassVars < Cop
         MSG = 'Replace class var %<class_var>s with a class ' \
               'instance var.'
@@ -38,6 +53,12 @@ def on_cvasgn(node)
           add_offense(node, location: :name)
         end
 
+        def on_send(node)
+          return unless node.method?(:class_variable_set)
+
+          add_offense(node.first_argument)
+        end
+
         def message(node)
           class_var, = *node
           format(MSG, class_var: class_var)

spec/rubocop/cop/style/class_vars_spec.rb

@@ -10,6 +10,23 @@ class TestClass; @@test = 10; end
     RUBY
   end
 
+  it 'registers an offense for class variable set in class' do
+    expect_offense(<<~RUBY)
+      class TestClass
+        class_variable_set(:@@test, 2)
+                           ^^^^^^^ Replace class var @@test with a class instance var.
+      end
+    RUBY
+  end
+
+  it 'registers an offense for class variable set on class receiver' do
+    expect_offense(<<~RUBY)
+      class TestClass; end
+      TestClass.class_variable_set(:@@test, 42)
+                                   ^^^^^^^ Replace class var @@test with a class instance var.
+    RUBY
+  end
+
   it 'does not register an offense for class variable usage' do
     expect_no_offenses('@@test.test(20)')
   end