[Fix rubocop#118] Fix a false positive for DeletePrefix and `Delete…

…Prefix` cops

Fixes rubocop#118.

Fix a false positive for `Performance/DeletePrefix` and `Performance/DeletePrefix` cops
when using heredoc.

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Bug fixes
 
 * [#111](/~https://github.com/rubocop-hq/rubocop-performance/issues/111): Fix an error for `Performance/DeletePrefix` and `Performance/DeleteSuffix` cops when using autocorrection with RuboCop 0.81 or lower. ([@koic][])
+* [#118](/~https://github.com/rubocop-hq/rubocop-performance/issues/118): Fix a false positive for `Performance/DeletePrefix` and `Performance/DeleteSuffix` cops when using heredoc. ([@koic][])
 
 ## 1.6.0 (2020-05-22)
 

lib/rubocop/cop/performance/delete_prefix.rb

@@ -43,6 +43,7 @@ class DeletePrefix < Cop
         def on_send(node)
           gsub_method?(node) do |_, bad_method, _, replace_string|
             return unless replace_string.blank?
+            return if node.receiver.respond_to?(:heredoc?) && node.receiver.heredoc?
 
             good_method = PREFERRED_METHODS[bad_method]
 

lib/rubocop/cop/performance/delete_suffix.rb

@@ -43,6 +43,7 @@ class DeleteSuffix < Cop
         def on_send(node)
           gsub_method?(node) do |_, bad_method, _, replace_string|
             return unless replace_string.blank?
+            return if node.receiver.respond_to?(:heredoc?) && node.receiver.heredoc?
 
             good_method = PREFERRED_METHODS[bad_method]
 

spec/rubocop/cop/performance/delete_prefix_spec.rb

@@ -94,6 +94,26 @@
       end
     end
 
+    context 'when using heredoc' do
+      it 'does not register an offense when using `\A` as starting pattern' do
+        expect_no_offenses(<<~RUBY)
+          puts <<~HEREDOC.gsub(/\\A   /, '')
+            foo
+            bar
+          HEREDOC
+        RUBY
+      end
+
+      it 'does not register an offense when using `^` as starting pattern' do
+        expect_no_offenses(<<~RUBY)
+          puts <<~HEREDOC.gsub(/^   /, '')
+            foo
+            bar
+          HEREDOC
+        RUBY
+      end
+    end
+
     context 'when using a non-blank string as replacement string' do
       it 'does not register an offense and corrects when using `gsub`' do
         expect_no_offenses(<<~RUBY)

spec/rubocop/cop/performance/delete_suffix_spec.rb

@@ -94,6 +94,26 @@
       end
     end
 
+    context 'when using heredoc' do
+      it 'does not register an offense when using `\z` as ending pattern' do
+        expect_no_offenses(<<~RUBY)
+          puts <<~HEREDOC.gsub(/   \\z/, '')
+            foo
+            bar
+          HEREDOC
+        RUBY
+      end
+
+      it 'does not register an offense when using `$` as ending pattern' do
+        expect_no_offenses(<<~RUBY)
+          puts <<~HEREDOC.gsub(/   $/, '')
+            foo
+            bar
+          HEREDOC
+        RUBY
+      end
+    end
+
     context 'when using a non-blank string as replacement string' do
       it 'does not register an offense and corrects when using `gsub`' do
         expect_no_offenses(<<~RUBY)