clang-tools-extra/clang-tidy/readability/RedundantStringInitCheck.cpp

   1 //===- RedundantStringInitCheck.cpp - clang-tidy ----------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "RedundantStringInitCheck.h"
  10 #include "../utils/Matchers.h"
  11 #include "../utils/OptionsUtils.h"
  12 #include "clang/ASTMatchers/ASTMatchers.h"
  13
  14 using namespace clang::ast_matchers;
  15 using namespace clang::tidy::matchers;
  16
  17 namespace clang {
  18 namespace tidy {
  19 namespace readability {
  20
  21 const char DefaultStringNames[] =
  22     "::std::basic_string_view;::std::basic_string";
  23
  24 static std::vector<StringRef> removeNamespaces(ArrayRef<StringRef> Names) {
  25   std::vector<StringRef> Result;
  26   Result.reserve(Names.size());
  27   for (StringRef Name : Names) {
  28     StringRef::size_type ColonPos = Name.rfind(':');
  29     Result.push_back(
  30         Name.drop_front(ColonPos == StringRef::npos ? 0 : ColonPos + 1));
  31   }
  32   return Result;
  33 }
  34
  35 static const CXXConstructExpr *
  36 getConstructExpr(const CXXCtorInitializer &CtorInit) {
  37   const Expr *InitExpr = CtorInit.getInit();
  38   if (const auto *CleanUpExpr = dyn_cast<ExprWithCleanups>(InitExpr))
  39     InitExpr = CleanUpExpr->getSubExpr();
  40   return dyn_cast<CXXConstructExpr>(InitExpr);
  41 }
  42
  43 static llvm::Optional<SourceRange>
  44 getConstructExprArgRange(const CXXConstructExpr &Construct) {
  45   SourceLocation B, E;
  46   for (const Expr *Arg : Construct.arguments()) {
  47     if (B.isInvalid())
  48       B = Arg->getBeginLoc();
  49     if (Arg->getEndLoc().isValid())
  50       E = Arg->getEndLoc();
  51   }
  52   if (B.isInvalid() || E.isInvalid())
  53     return llvm::None;
  54   return SourceRange(B, E);
  55 }
  56
  57 RedundantStringInitCheck::RedundantStringInitCheck(StringRef Name,
  58                                                    ClangTidyContext *Context)
  59     : ClangTidyCheck(Name, Context),
  60       StringNames(utils::options::parseStringList(
  61           Options.get("StringNames", DefaultStringNames))) {}
  62
  63 void RedundantStringInitCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
  64   Options.store(Opts, "StringNames", DefaultStringNames);
  65 }
  66
  67 void RedundantStringInitCheck::registerMatchers(MatchFinder *Finder) {
  68   const auto HasStringTypeName = hasAnyName(StringNames);
  69   const auto HasStringCtorName = hasAnyName(removeNamespaces(StringNames));
  70
  71   // Match string constructor.
  72   const auto StringConstructorExpr = expr(
  73       anyOf(cxxConstructExpr(argumentCountIs(1),
  74                              hasDeclaration(cxxMethodDecl(HasStringCtorName))),
  75             // If present, the second argument is the alloc object which must
  76             // not be present explicitly.
  77             cxxConstructExpr(argumentCountIs(2),
  78                              hasDeclaration(cxxMethodDecl(HasStringCtorName)),
  79                              hasArgument(1, cxxDefaultArgExpr()))));
  80
  81   // Match a string constructor expression with an empty string literal.
  82   const auto EmptyStringCtorExpr = cxxConstructExpr(
  83       StringConstructorExpr,
  84       hasArgument(0, ignoringParenImpCasts(stringLiteral(hasSize(0)))));
  85
  86   const auto EmptyStringCtorExprWithTemporaries =
  87       cxxConstructExpr(StringConstructorExpr,
  88                        hasArgument(0, ignoringImplicit(EmptyStringCtorExpr)));
  89
  90   const auto StringType = hasType(hasUnqualifiedDesugaredType(
  91       recordType(hasDeclaration(cxxRecordDecl(HasStringTypeName)))));
  92   const auto EmptyStringInit = traverse(
  93       TK_AsIs, expr(ignoringImplicit(anyOf(
  94                    EmptyStringCtorExpr, EmptyStringCtorExprWithTemporaries))));
  95
  96   // Match a variable declaration with an empty string literal as initializer.
  97   // Examples:
  98   //     string foo = "";
  99   //     string bar("");
 100   Finder->addMatcher(
 101       traverse(TK_AsIs,
 102                namedDecl(varDecl(StringType, hasInitializer(EmptyStringInit))
 103                              .bind("vardecl"),
 104                          unless(parmVarDecl()))),
 105       this);
 106   // Match a field declaration with an empty string literal as initializer.
 107   Finder->addMatcher(
 108       namedDecl(fieldDecl(StringType, hasInClassInitializer(EmptyStringInit))
 109                     .bind("fieldDecl")),
 110       this);
 111   // Matches Constructor Initializers with an empty string literal as
 112   // initializer.
 113   // Examples:
 114   //     Foo() : SomeString("") {}
 115   Finder->addMatcher(
 116       cxxCtorInitializer(
 117           isWritten(),
 118           forField(allOf(StringType, optionally(hasInClassInitializer(
 119                                          EmptyStringInit.bind("empty_init"))))),
 120           withInitializer(EmptyStringInit))
 121           .bind("ctorInit"),
 122       this);
 123 }
 124
 125 void RedundantStringInitCheck::check(const MatchFinder::MatchResult &Result) {
 126   if (const auto *VDecl = Result.Nodes.getNodeAs<VarDecl>("vardecl")) {
 127     // VarDecl's getSourceRange() spans 'string foo = ""' or 'string bar("")'.
 128     // So start at getLocation() to span just 'foo = ""' or 'bar("")'.
 129     SourceRange ReplaceRange(VDecl->getLocation(), VDecl->getEndLoc());
 130     diag(VDecl->getLocation(), "redundant string initialization")
 131         << FixItHint::CreateReplacement(ReplaceRange, VDecl->getName());
 132   }
 133   if (const auto *FDecl = Result.Nodes.getNodeAs<FieldDecl>("fieldDecl")) {
 134     // FieldDecl's getSourceRange() spans 'string foo = ""'.
 135     // So start at getLocation() to span just 'foo = ""'.
 136     SourceRange ReplaceRange(FDecl->getLocation(), FDecl->getEndLoc());
 137     diag(FDecl->getLocation(), "redundant string initialization")
 138         << FixItHint::CreateReplacement(ReplaceRange, FDecl->getName());
 139   }
 140   if (const auto *CtorInit =
 141           Result.Nodes.getNodeAs<CXXCtorInitializer>("ctorInit")) {
 142     if (const FieldDecl *Member = CtorInit->getMember()) {
 143       if (!Member->hasInClassInitializer() ||
 144           Result.Nodes.getNodeAs<Expr>("empty_init")) {
 145         // The String isn't declared in the class with an initializer or its
 146         // declared with a redundant initializer, which will be removed. Either
 147         // way the string will be default initialized, therefore we can remove
 148         // the constructor initializer entirely.
 149         diag(CtorInit->getMemberLocation(), "redundant string initialization")
 150             << FixItHint::CreateRemoval(CtorInit->getSourceRange());
 151         return;
 152       }
 153     }
 154     const CXXConstructExpr *Construct = getConstructExpr(*CtorInit);
 155     if (!Construct)
 156       return;
 157     if (llvm::Optional<SourceRange> RemovalRange =
 158             getConstructExprArgRange(*Construct))
 159       diag(CtorInit->getMemberLocation(), "redundant string initialization")
 160           << FixItHint::CreateRemoval(*RemovalRange);
 161   }
 162 }
 163
 164 } // namespace readability
 165 } // namespace tidy
 166 } // namespace clang