PreferSingleCharOverloadsCheck.cpp

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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#include "PreferSingleCharOverloadsCheck.h"
#include "../utils/CheckUtils.h"
#include "../utils/OptionsUtils.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <optional>
 
using namespace clang::ast_matchers;
 
namespace clang::tidy::performance {
 
namespace {
 
constexpr llvm::StringLiteral DeprecatedCheckName =
    "performance-faster-string-find";
constexpr llvm::StringLiteral CanonicalCheckName =
    "performance-prefer-single-char-overloads";
 
} // namespace
 
static std::optional<std::string>
makeCharacterLiteral(const StringLiteral *Literal) {
  std::string Result;
  {
    llvm::raw_string_ostream OS(Result);
    Literal->outputString(OS);
  }
  // Now replace the " with '.
  const auto OpenPos = Result.find_first_of('"');
  if (OpenPos == std::string::npos)
    return std::nullopt;
  Result[OpenPos] = '\'';
 
  const auto ClosePos = Result.find_last_of('"');
  if (ClosePos == std::string::npos)
    return std::nullopt;
  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;
}
 
PreferSingleCharOverloadsCheck::PreferSingleCharOverloadsCheck(
    StringRef Name, ClangTidyContext *Context)
    : ClangTidyCheck(Name, Context),
      StringLikeClasses(utils::options::parseStringList(
          Options.get("StringLikeClasses",
                      "::std::basic_string;::std::basic_string_view"))) {
  if (Name == DeprecatedCheckName)
    utils::diagDeprecatedCheckAlias(*this, *Context, DeprecatedCheckName,
                                    CanonicalCheckName);
}
 
void PreferSingleCharOverloadsCheck::storeOptions(
    ClangTidyOptions::OptionMap &Opts) {
  Options.store(Opts, "StringLikeClasses",
                utils::options::serializeStringList(StringLikeClasses));
}
 
void PreferSingleCharOverloadsCheck::registerMatchers(MatchFinder *Finder) {
  const auto SingleChar =
      ignoringParenCasts(stringLiteral(hasSize(1)).bind("literal"));
 
  const auto StringExpr = expr(hasType(hasUnqualifiedDesugaredType(
      recordType(hasDeclaration(recordDecl(hasAnyName(StringLikeClasses)))))));
 
  const auto InterestingStringFunction = hasAnyName(
      "find", "rfind", "find_first_of", "find_first_not_of", "find_last_of",
      "find_last_not_of", "starts_with", "ends_with", "contains", "operator+=");
 
  Finder->addMatcher(
      cxxMemberCallExpr(
          callee(functionDecl(InterestingStringFunction).bind("func")),
          anyOf(argumentCountIs(1), argumentCountIs(2)),
          hasArgument(0, SingleChar), on(StringExpr)),
      this);
 
  Finder->addMatcher(cxxOperatorCallExpr(hasOperatorName("+="),
                                         hasLHS(StringExpr), hasRHS(SingleChar),
                                         callee(functionDecl().bind("func"))),
                     this);
}
 
void PreferSingleCharOverloadsCheck::check(
    const MatchFinder::MatchResult &Result) {
  const auto *Literal = Result.Nodes.getNodeAs<StringLiteral>("literal");
  const auto *FindFunc = Result.Nodes.getNodeAs<FunctionDecl>("func");
 
  auto Replacement = makeCharacterLiteral(Literal);
  if (!Replacement)
    return;
 
  const auto Diag = diag(Literal->getBeginLoc(),
                         "%0 called with a string literal consisting of "
                         "a single character; consider using the more "
                         "efficient overload accepting a character")
                    << FindFunc;
  if (std::none_of(Literal->tokloc_begin(), Literal->tokloc_end(),
                   [](SourceLocation Loc) { return Loc.isMacroID(); }))
    Diag << FixItHint::CreateReplacement(Literal->getSourceRange(),
                                         *Replacement);
}
 
} // namespace clang::tidy::performance