[Fix #190] Fix Rails/SaveBang when return value is checked immediately

Fixes #190.

Rails/SaveBang had a false positive when the return value of a `create`
call was checked directly with a call to `persisted?`.

Author: jas14

.rubocop_todo.yml

@@ -1,6 +1,6 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2019-09-13 11:45:19 -0400 using RuboCop version 0.74.0.
+# on 2020-01-22 14:25:37 -0500 using RuboCop version 0.79.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
@@ -14,27 +14,27 @@ InternalAffairs/NodeDestructuring:
     - 'lib/rubocop/cop/rails/relative_date_constant.rb'
     - 'lib/rubocop/cop/rails/time_zone.rb'
 
-# Offense count: 11
+# Offense count: 10
 Metrics/AbcSize:
   Max: 17
 
 # Offense count: 4
 # Configuration parameters: CountComments.
 Metrics/ClassLength:
-  Max: 169
+  Max: 173
 
-# Offense count: 25
+# Offense count: 26
 # Configuration parameters: CountComments, ExcludedMethods.
 Metrics/MethodLength:
   Max: 14
 
-# Offense count: 73
+# Offense count: 77
 # Configuration parameters: Prefixes.
 # Prefixes: when, with, without
 RSpec/ContextWording:
   Enabled: false
 
-# Offense count: 277
+# Offense count: 287
 # Configuration parameters: Max.
 RSpec/ExampleLength:
   Enabled: false

CHANGELOG.md

@@ -7,6 +7,7 @@
 * [#184](https://github.com/rubocop-hq/rubocop-rails/issues/184): Fix `Rake/Environment` to allow task with no block. ([@hanachin][])
 * [#122](https://github.com/rubocop-hq/rubocop-rails/issues/122): Fix `Exclude` paths that were not inherited. ([@koic][])
 * [#187](https://github.com/rubocop-hq/rubocop-rails/pull/187): Fix an issue that excluded files in rubocop-rails did not work. ([@sinsoku][])
+* [#190](https://github.com/rubocop-hq/rubocop-rails/issues/190): Fix `Rails/SaveBang` when return value is checked immediately. ([@jas14][])
 
 ## 2.4.1 (2019-12-25)
 

lib/rubocop/cop/rails/save_bang.rb

@@ -12,7 +12,8 @@ module Rails
       # - update or save calls, assigned to a variable,
       #   or used as a condition in an if/unless/case statement.
       # - create calls, assigned to a variable that then has a
-      #   call to `persisted?`.
+      #   call to `persisted?`, or whose return value is checked by
+      #   `persisted?` immediately
       # - calls if the result is explicitly returned from methods and blocks,
       #   or provided as arguments.
       # - calls whose signature doesn't look like an ActiveRecord
@@ -137,16 +138,19 @@ def check_assignment(assignment)
           add_offense_for_node(node, CREATE_MSG)
         end
 
-        def on_send(node) # rubocop:disable Metrics/CyclomaticComplexity
+        # rubocop:disable Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
+        def on_send(node)
           return unless persist_method?(node)
           return if return_value_assigned?(node)
           return if implicit_return?(node)
           return if check_used_in_condition_or_compound_boolean(node)
           return if argument?(node)
           return if explicit_return?(node)
+          return if checked_immediately?(node)
 
           add_offense_for_node(node)
         end
+        # rubocop:enable Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
         alias on_csend on_send
 
         def autocorrect(node)
@@ -238,6 +242,10 @@ def conditional?(parent)
           parent.if_type? || parent.case_type?
         end
 
+        def checked_immediately?(node)
+          node.parent && call_to_persisted?(node.parent)
+        end
+
         def allowed_receiver?(node)
           return false unless node.receiver
           return false unless cop_config['AllowedReceivers']

manual/cops_rails.md

@@ -2193,7 +2193,8 @@ This will allow:
 - update or save calls, assigned to a variable,
   or used as a condition in an if/unless/case statement.
 - create calls, assigned to a variable that then has a
-  call to `persisted?`.
+  call to `persisted?`, or whose return value is checked by
+  `persisted?` immediately
 - calls if the result is explicitly returned from methods and blocks,
   or provided as arguments.
 - calls whose signature doesn't look like an ActiveRecord

spec/rubocop/cop/rails/save_bang_spec.rb

@@ -571,6 +571,12 @@ def whatever
       RUBY
     end
 
+    it "when using persisted? directly on #{method} return value" do
+      expect_no_offenses(<<~RUBY)
+        return unless object.#{method}.persisted?
+      RUBY
+    end
+
     it "when using #{method} with `||`" do
       expect_no_offenses(<<~RUBY)
         def find_or_create(**opts)