Fix a false positive for Lint/ParenthesesAsGroupedExpression

This PR fixes a false positive for `Lint/ParenthesesAsGroupedExpression` when using an intended grouped parentheses. ```ruby puts (2 + 3) * 4 ``` I noticed this false positive in implementing this cop's auto-correction. So, I plan to open a PR that implements auto-correction separately from this PR.
rubocop · May 7, 2020 · 5d5cf77 · 5d5cf77
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -20,6 +20,7 @@
 * [#7903](https://github.com/rubocop-hq/rubocop/pull/7903): Fix an incorrect autocorrect for `Style/HashTransformKeys` and `Style/HashTransformValues` cops when line break before `to_h` method. ([@diogoosorio][], [@koic][])
 * [#7899](https://github.com/rubocop-hq/rubocop/issues/7899): Fix an infinite loop error for `Layout/SpaceAroundOperators` with `Layout/ExtraSpacing` when using `ForceEqualSignAlignment: true`. ([@koic][])
 * [#7885](https://github.com/rubocop-hq/rubocop/issues/7885): Fix `Style/IfUnlessModifier` logic when tabs are used for indentation. ([@jonas054][])
+* [#7909](https://github.com/rubocop-hq/rubocop/pull/7909): Fix a false positive for `Lint/ParenthesesAsGroupedExpression` when using an intended grouped parentheses. ([@koic][])
 
 ### Changes
 

diff --git a/lib/rubocop/cop/lint/parentheses_as_grouped_expression.rb b/lib/rubocop/cop/lint/parentheses_as_grouped_expression.rb
@@ -9,14 +9,12 @@ module Lint
       # @example
       #
       #   # bad
-      #
-      #   puts (x + y)
-      #
-      # @example
+      #   do_something (foo)
       #
       #   # good
-      #
-      #   puts(x + y)
+      #   do_something(foo)
+      #   do_something (2 + 3) * 4
+      #   do_something (foo * bar).baz
       class ParenthesesAsGroupedExpression < Cop
         include RangeHelp
 
@@ -25,8 +23,7 @@ class ParenthesesAsGroupedExpression < Cop
         def on_send(node)
           return unless node.arguments.one?
           return if node.operator_method? || node.setter_method?
-
-          return unless node.first_argument.source.start_with?('(')
+          return if grouped_parentheses?(node)
 
           space_length = spaces_before_left_parenthesis(node)
           return unless space_length.positive?
@@ -39,6 +36,12 @@ def on_send(node)
 
         private
 
+        def grouped_parentheses?(node)
+          first_argument = node.first_argument
+
+          first_argument.send_type? && first_argument.receiver&.begin_type?
+        end
+
         def spaces_before_left_parenthesis(node)
           receiver = node.receiver
           receiver_length = if receiver

diff --git a/manual/cops_lint.md b/manual/cops_lint.md
@@ -1424,13 +1424,12 @@ parenthesis.
 
 ```ruby
 # bad
+do_something (foo)
 
-puts (x + y)
-```
-```ruby
 # good
-
-puts(x + y)
+do_something(foo)
+do_something (2 + 3) * 4
+do_something (foo * bar).baz
 ```
 
 ### References

diff --git a/spec/rubocop/cop/lint/parentheses_as_grouped_expression_spec.rb b/spec/rubocop/cop/lint/parentheses_as_grouped_expression_spec.rb
@@ -19,10 +19,15 @@
     RUBY
   end
 
-  it 'registers an offense for math expression' do
-    expect_offense(<<~RUBY)
+  it 'does not register an offense for math expression' do
+    expect_no_offenses(<<~RUBY)
       puts (2 + 3) * 4
-          ^ `(...)` interpreted as grouped expression.
+    RUBY
+  end
+
+  it 'does not register an offense for math expression with `to_i`' do
+    expect_no_offenses(<<~RUBY)
+      do_something.eq (foo * bar).to_i
     RUBY
   end