Enable autocorrection for Style/DateTime.

CHANGELOG.md

@@ -6,6 +6,10 @@
 
 * [#8774](https://github.com/rubocop-hq/rubocop/issues/8774): Fix a false positive for `Layout/ArrayAlignment` with parallel assignment. ([@dvandersluis][])
 
+### Changes
+
+* [#8738](https://github.com/rubocop-hq/rubocop/issues/8738): Add autocorrection to `Style/DateTime`. ([@dvandersluis][])
+
 ## 0.91.1 (2020-09-23)
 
 ### Bug fixes

config/default.yml

@@ -2863,7 +2863,8 @@ Style/DateTime:
   StyleGuide: '#date--time'
   Enabled: false
   VersionAdded: '0.51'
-  VersionChanged: '0.59'
+  VersionChanged: '0.92'
+  SafeAutoCorrect: false
   AllowCoercion: false
 
 Style/DefWithParentheses:

docs/modules/ROOT/pages/cops_style.adoc

@@ -1879,9 +1879,9 @@ an offense is reported.
 
 | Disabled
 | Yes
-| No
+| Yes (Unsafe)
 | 0.51
-| 0.59
+| 0.92
 |===
 
 This cop checks for consistent usage of the `DateTime` class over the

lib/rubocop/cop/style/date_time.rb

@@ -42,6 +42,8 @@ module Style
       #   # good
       #   something.to_time
       class DateTime < Base
+        extend AutoCorrector
+
         CLASS_MSG = 'Prefer Time over DateTime.'
         COERCION_MSG = 'Do not use #to_datetime.'
 
@@ -63,14 +65,23 @@ def on_send(node)
           return if historic_date?(node)
 
           message = to_datetime?(node) ? COERCION_MSG : CLASS_MSG
-          add_offense(node, message: message)
+
+          add_offense(node, message: message) do |corrector|
+            autocorrect(corrector, node)
+          end
         end
 
         private
 
         def disallow_coercion?
           !cop_config['AllowCoercion']
         end
+
+        def autocorrect(corrector, node)
+          return if to_datetime?(node)
+
+          corrector.replace(node.receiver.loc.name, 'Time')
+        end
       end
     end
   end

spec/rubocop/cop/style/date_time_spec.rb

@@ -8,20 +8,32 @@
       DateTime.now
       ^^^^^^^^^^^^ Prefer Time over DateTime.
     RUBY
+
+    expect_correction(<<~RUBY)
+      Time.now
+    RUBY
   end
 
   it 'registers an offense when using ::DateTime for current time' do
     expect_offense(<<~RUBY)
       ::DateTime.now
       ^^^^^^^^^^^^^^ Prefer Time over DateTime.
     RUBY
+
+    expect_correction(<<~RUBY)
+      ::Time.now
+    RUBY
   end
 
   it 'registers an offense when using DateTime for modern date' do
     expect_offense(<<~RUBY)
       DateTime.iso8601('2016-06-29')
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer Time over DateTime.
     RUBY
+
+    expect_correction(<<~RUBY)
+      Time.iso8601('2016-06-29')
+    RUBY
   end
 
   it 'does not register an offense when using Time for current time' do