Fix false negative for != comparison in Rails/UnknownEnv

Author: lovro-bikic

changelog/change_rails_unknown_env_support_for_inequality_comparison.md

@@ -0,0 +1 @@
+* [#1592](https://github.com/rubocop/rubocop-rails/pull/1592): Fix false negative for `!=` comparison in `Rails/UnknownEnv`. ([@lovro-bikic][])

lib/rubocop/cop/rails/unknown_env.rb

@@ -13,10 +13,12 @@ module Rails
       #   # bad
       #   Rails.env.proudction?
       #   Rails.env == 'proudction'
+      #   Rails.env != 'proudction'
       #
       #   # good
       #   Rails.env.production?
       #   Rails.env == 'production'
+      #   Rails.env != 'production'
       #
       # @example
       #   # bad
@@ -47,8 +49,8 @@ class UnknownEnv < Base
 
         def_node_matcher :unknown_environment_equal?, <<~PATTERN
           {
-            (send #rails_env? {:== :===} $(str #unknown_env_name?))
-            (send $(str #unknown_env_name?) {:== :===} #rails_env?)
+            (send #rails_env? {:== :=== :!=} $(str #unknown_env_name?))
+            (send $(str #unknown_env_name?) {:== :=== :!=} #rails_env?)
           }
         PATTERN
 

spec/rubocop/cop/rails/unknown_env_spec.rb

@@ -44,6 +44,15 @@
         RUBY
       end
 
+      it 'registers an offense for typo of environment name with `!=` operator' do
+        expect_offense(<<~RUBY)
+          Rails.env != 'proudction'
+                       ^^^^^^^^^^^^ Unknown environment `proudction`. Did you mean `production`?
+          'developpment' != Rails.env
+          ^^^^^^^^^^^^^^ Unknown environment `developpment`. Did you mean `development`?
+        RUBY
+      end
+
       it 'registers an offense when case condition is an unknown environment name' do
         expect_offense(<<~RUBY)
           case Rails.env