[Fix #222] Fix a false positive for `Performance/RedundantSplitRegexp…

…Argument`

Fixes #222.

This PR fixes a false positive for `Performance/RedundantSplitRegexpArgument`
when `split` method argument is exactly one spece regexp `/ /`.

CHANGELOG.md

@@ -8,6 +8,7 @@
 * [#36](https://github.com/rubocop/rubocop-performance/issues/36): Fix a false positive for `Performance/ReverseEach` when `each` is called on `reverse` and using the result value. ([@koic][])
 * [#224](https://github.com/rubocop/rubocop-performance/pull/224): Fix a false positive for `Style/RedundantEqualityComparisonBlock` when using one argument with comma separator in block argument. ([@koic][])
 * [#225](https://github.com/rubocop/rubocop-performance/issues/225): Fix a false positive for `Style/RedundantEqualityComparisonBlock` when using `any?` with `===` comparison block and block argument is not used as a receiver for `===`. ([@koic][])
+* [#222](https://github.com/rubocop/rubocop-performance/issues/222): Fix a false positive for `Performance/RedundantSplitRegexpArgument` when `split` method argument is exactly one spece regexp `/ /`. ([@koic][])
 
 ## 1.10.1 (2021-03-02)
 

lib/rubocop/cop/performance/redundant_split_regexp_argument.rb

@@ -26,7 +26,7 @@ class RedundantSplitRegexpArgument < Base
 
         def on_send(node)
           return unless (regexp_node = split_call_with_regexp?(node))
-          return if regexp_node.ignore_case?
+          return if regexp_node.ignore_case? || regexp_node.content == ' '
           return unless determinist_regexp?(regexp_node)
 
           add_offense(regexp_node) do |corrector|

spec/rubocop/cop/performance/redundant_split_regexp_argument_spec.rb

@@ -17,6 +17,12 @@
     expect_no_offenses("'fooSplitbar'.split(/split/i)")
   end
 
+  it 'accepts when `split` method argument is exactly one spece regexp `/ /`' do
+    expect_no_offenses(<<~RUBY)
+      'foo         bar'.split(/ /)
+    RUBY
+  end
+
   it 'registers an offense when the method is split and correctly removes escaping characters' do
     expect_offense(<<~RUBY)
       'a,b,c'.split(/\\./)
@@ -82,4 +88,15 @@
       'a,b,c'.split(",")
     RUBY
   end
+
+  it 'registers and corrects an offense when `split` method argument is two or more speces regexp `/  /`' do
+    expect_offense(<<~RUBY)
+      'foo         bar'.split(/  /)
+                              ^^^^ Use string as argument instead of regexp.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      'foo         bar'.split("  ")
+    RUBY
+  end
 end