[clang-tidy] `performance-faster-string-find` generates incorrect fixes for single quote character literals

[fwolff]

Summary

"'" is turned into ''' but should be turned into '\''.

[PiotrZSL]

clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.cpp

40

clang-tools-extra/docs/ReleaseNotes.rst

199–201

And put it before performanc-noexcept-swap, other alternative would be to call it "Improve XYZ check to properly escape single quote characters. or something like that

[PiotrZSL]

LGTM

clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.cpp

 
 std::optional<std::string> makeCharacterLiteral(const StringLiteral *Literal) {
   std::string Result;
   {
     llvm::raw_string_ostream OS(Result);
     Literal->outputString(OS);
   }
   // Now replace the " with '.
-  auto Pos = Result.find_first_of('"');
-  if (Pos == Result.npos)
+  auto OpenPos = Result.find_first_of('"');
+  if (OpenPos == Result.npos)
     return std::nullopt;
-  Result[Pos] = '\'';
-  Pos = Result.find_last_of('"');
-  if (Pos == Result.npos)
+  Result[OpenPos] = '\'';
+
+  auto ClosePos = Result.find_last_of('"');
+  if (ClosePos == Result.npos)
     return std::nullopt;
-  Result[Pos] = '\'';
+  Result[ClosePos] = '\'';
+
+  // "'" is OK, but ''' is not, so add a backslash
+  if (ClosePos - OpenPos == 2 && Result[OpenPos + 1] == '\'')
+    Result.replace(OpenPos + 1, 1, "\\'");
+
   return Result;
 }
 
 AST_MATCHER_FUNCTION(ast_matchers::internal::Matcher<Expr>,
                      hasSubstitutedType) {
   return hasType(qualType(anyOf(substTemplateTypeParmType(),
                                 hasDescendant(substTemplateTypeParmType()))));
 }

clang-tools-extra/docs/ReleaseNotes.rst

 - Improved :doc:`performanc-noexcept-swap
   <clang-tidy/checks/performance/noexcept-swap>` check to enforce a stricter
   match with the swap function signature, eliminating false-positives.
 
 - Improved :doc:`readability-identifier-naming
   <clang-tidy/checks/readability/identifier-naming>` check to emit proper
   warnings when a type forward declaration precedes its definition.
 
+- Fixed a bug in :doc:`performance-faster-string-find
+  <performance-faster-string-find>` which generated incorrect fixes by not
+  escaping single quotes properly.
+
 Removed checks
 ^^^^^^^^^^^^^^
 
 Improvements to include-fixer
 -----------------------------
 
 The improvements are...
 

clang-tools-extra/test/clang-tidy/checkers/performance/faster-string-find.cpp

void StringFind() {
   // CHECK-MESSAGES: [[@LINE-1]]:12: warning: 'find' called with a string literal consisting of a single character; consider using the more effective overload accepting a character [performance-faster-string-find]
   // CHECK-FIXES: Str.find('a');
 
   // Works with the pos argument.
   Str.find("a", 1);
   // CHECK-MESSAGES: [[@LINE-1]]:12: warning: 'find' called with a string literal
   // CHECK-FIXES: Str.find('a', 1);
 
-  // Doens't work with strings smaller or larger than 1 char.
+  // Doesn't work with strings smaller or larger than 1 char.
   Str.find("");
   Str.find("ab");
 
   // Doesn't do anything with the 3 argument overload.
   Str.find("a", 1, 1);
 
+  // Single quotes are escaped properly
+  Str.find("'");
+  // CHECK-MESSAGES: [[@LINE-1]]:12: warning: 'find' called with a string literal
+  // CHECK-FIXES: Str.find('\'');
+  Str.find("\'");
+  // CHECK-MESSAGES: [[@LINE-1]]:12: warning: 'find' called with a string literal
+  // CHECK-FIXES: Str.find('\'');
+
   // Other methods that can also be replaced
   Str.rfind("a");
   // CHECK-MESSAGES: [[@LINE-1]]:13: warning: 'rfind' called with a string literal
   // CHECK-FIXES: Str.rfind('a');
   Str.find_first_of("a");
   // CHECK-MESSAGES: [[@LINE-1]]:21: warning: 'find_first_of' called with a string
   // CHECK-FIXES: Str.find_first_of('a');
   Str.find_first_not_of("a");