[Fix rubocop#120] Fix save-in-conditional checking in Rails/SaveBang

Fixes rubocop#120.

The Rails/SaveBang rule emitted incorrect errors about using the return
value of save-like calls in conditional nodes. It did not differentiate
between such calls in the body versus the condition, where only the
latter is necessarily a boolean expression.

.rubocop_todo.yml

@@ -1,6 +1,6 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2019-07-20 17:51:45 +0900 using RuboCop version 0.72.0.
+# on 2019-08-28 11:48:06 -0400 using RuboCop version 0.74.0.
 # 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
@@ -14,16 +14,16 @@ InternalAffairs/NodeDestructuring:
  - 'lib/rubocop/cop/rails/relative_date_constant.rb'
  - 'lib/rubocop/cop/rails/time_zone.rb'
 
-# Offense count: 9
+# Offense count: 10
 Metrics/AbcSize:
  Max: 17
 
 # Offense count: 4
 # Configuration parameters: CountComments.
 Metrics/ClassLength:
- Max: 164
+ Max: 168
 
-# Offense count: 23
+# Offense count: 24
 # Configuration parameters: CountComments, ExcludedMethods.
 Metrics/MethodLength:
  Max: 14
@@ -34,7 +34,7 @@ Metrics/MethodLength:
 RSpec/ContextWording:
  Enabled: false
 
-# Offense count: 261
+# Offense count: 264
 # Configuration parameters: Max.
 RSpec/ExampleLength:
  Enabled: false

CHANGELOG.md

@@ -12,6 +12,8 @@
 
 * [#118](https://github.com/rubocop-hq/rubocop-rails/issues/118): Fix an incorrect autocorrect for `Rails/Validation` when attributes are specified with array literal. ([@koic][])
 * [#116](https://github.com/rubocop-hq/rubocop-rails/issues/116): Fix an incorrect autocorrect for `Rails/Presence` when `else` branch of ternary operator is not nil. ([@koic][])
+### Bug fixes
+* [#120](https://github.com/rubocop-hq/rubocop-rails/issues/120): Fix save-as-conditional checking. ([@jas14][])
 
 ## 2.3.1 (2019-08-26)
 
@@ -85,3 +87,4 @@
 [@prathamesh-sonpatki]: https://github.com/prathamesh-sonpatki
 [@MaximeLaurenty]: https://github.com/MaximeLaurenty
 [@eugeneius]: https://github.com/eugeneius
+[@jas14]: https://github.com/jas14

lib/rubocop/cop/rails/save_bang.rb

@@ -212,7 +212,7 @@ def array_parent(node)
  end
 
  def check_used_in_conditional(node)
- return false unless conditional?(node)
+ return false unless in_boolean_expr?(node)
 
  unless MODIFY_PERSIST_METHODS.include?(node.method_name)
  add_offense_for_node(node, CREATE_CONDITIONAL_MSG)
@@ -221,15 +221,20 @@ def check_used_in_conditional(node)
  true
  end
 
- def conditional?(node) # rubocop:disable Metrics/CyclomaticComplexity
+ def in_boolean_expr?(node)
  node = node.block_node || node
+ parent = node.parent
+ return false unless parent
 
- condition = node.parent
- return false unless condition
+ predicate_node?(parent) || condition_of?(parent, node)
+ end
+
+ def predicate_node?(node)
+ node.or_type? || node.and_type? || single_negative?(node)
+ end
 
- condition.if_type? || condition.case_type? ||
- condition.or_type? || condition.and_type? ||
- single_negative?(condition)
+ def condition_of?(parent, node)
+ (parent.if_type? || parent.case_type?) && node == parent.condition
  end
 
  def allowed_receiver?(node)

spec/rubocop/cop/rails/save_bang_spec.rb

@@ -223,6 +223,14 @@
  end
  end
 
+ it "when using #{method} in the body of a oneline if" do
+ inspect_source("object.#{method} if false")
+
+ expect(cop.messages)
+ .to eq(["Use `#{method}!` instead of `#{method}` " \
+ 'if the return value is not checked.'])
+ end
+
  it "when using #{method} with a bunch of hashes & arrays" do
  inspect_source(<<~RUBY)
  return [{ success: object.#{method} }, true]