From b2fe007101dab711dd75ad4927bb5813e4411cf5 Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Tue, 2 Nov 2021 22:25:51 +0900
Subject: [PATCH] Fix a false positive for `Style/StringLiterals`

Follow up to https://github.com/rubocop/rubocop/pull/10166#issuecomment-956190960.

This PR fixes a false positive for `Style/StringLiterals` when `EnforcedStyle: double_quotes`
and using single quoted string with backslash.
It has moved a separate implementation for `Style/QuotedSymbols` to resolve #10152 to
`Style/QuotedSymbols` to prevent impact on `Style/StringLiterals`'s false positives.
---
 ...fix_a_false_positive_for_style_string_literals.md |  1 +
 lib/rubocop/cop/mixin/string_literals_help.rb        |  6 +-----
 lib/rubocop/cop/style/quoted_symbols.rb              | 12 +++++++++++-
 spec/rubocop/cop/style/string_literals_spec.rb       |  8 ++++++++
 4 files changed, 21 insertions(+), 6 deletions(-)
 create mode 100644 changelog/fix_a_false_positive_for_style_string_literals.md

diff --git a/changelog/fix_a_false_positive_for_style_string_literals.md b/changelog/fix_a_false_positive_for_style_string_literals.md
new file mode 100644
index 00000000000..5d634e80531
--- /dev/null
+++ b/changelog/fix_a_false_positive_for_style_string_literals.md
@@ -0,0 +1 @@
+* [#10229](https://github.com/rubocop/rubocop/pull/10229): Fix a false positive for `Style/StringLiterals` when `EnforcedStyle: double_quotes` and using single quoted string with backslash. ([@koic][])
diff --git a/lib/rubocop/cop/mixin/string_literals_help.rb b/lib/rubocop/cop/mixin/string_literals_help.rb
index fba7dceaad0..c43c08dc176 100644
--- a/lib/rubocop/cop/mixin/string_literals_help.rb
+++ b/lib/rubocop/cop/mixin/string_literals_help.rb
@@ -13,11 +13,7 @@ def wrong_quotes?(src_or_node)
         if style == :single_quotes
           !double_quotes_required?(src)
         else
-          # The string needs single quotes if:
-          # 1. It contains a double quote
-          # 2. It contains text that would become an escape sequence with double quotes
-          # 3. It contains text that would become an interpolation with double quotes
-          !/" | (?<!\\)\\[aAbcdefkMnprsStuUxzZ0-7] | \#[@{$]/x.match?(src)
+          !/" | \\[^'\\] | \#[@{$]/x.match?(src)
         end
       end
     end
diff --git a/lib/rubocop/cop/style/quoted_symbols.rb b/lib/rubocop/cop/style/quoted_symbols.rb
index dc337740d15..5bec035da0a 100644
--- a/lib/rubocop/cop/style/quoted_symbols.rb
+++ b/lib/rubocop/cop/style/quoted_symbols.rb
@@ -46,7 +46,7 @@ def on_sym(node)
 
           message = style == :single_quotes ? MSG_SINGLE : MSG_DOUBLE
 
-          if wrong_quotes?(node)
+          if wrong_quotes?(node) || invalid_double_quotes?(node.source)
             add_offense(node, message: message) do |corrector|
               opposite_style_detected
               autocorrect(corrector, node)
@@ -58,6 +58,16 @@ def on_sym(node)
 
         private
 
+        def invalid_double_quotes?(source)
+          return false unless style == :double_quotes
+
+          # The string needs single quotes if:
+          # 1. It contains a double quote
+          # 2. It contains text that would become an escape sequence with double quotes
+          # 3. It contains text that would become an interpolation with double quotes
+          !/" | (?<!\\)\\[aAbcdefkMnprsStuUxzZ0-7] | \#[@{$]/x.match?(source)
+        end
+
         def autocorrect(corrector, node)
           str = if hash_colon_key?(node)
                   # strip quotes
diff --git a/spec/rubocop/cop/style/string_literals_spec.rb b/spec/rubocop/cop/style/string_literals_spec.rb
index ff1b88ee937..c780bd8a768 100644
--- a/spec/rubocop/cop/style/string_literals_spec.rb
+++ b/spec/rubocop/cop/style/string_literals_spec.rb
@@ -254,6 +254,14 @@
       expect_no_offenses('a = %(x)')
     end
 
+    it 'accepts single quoted string with backslash' do
+      expect_no_offenses(<<~'RUBY')
+        '\,'
+        '100\%'
+        '(\)'
+      RUBY
+    end
+
     it 'accepts heredocs' do
       expect_no_offenses(<<~RUBY)
         execute <<-SQL