clang-tools-extra/clangd/refactor/tweaks/AddUsing.cpp

   1 //===--- AddUsing.cpp --------------------------------------------*- 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 "AST.h"
  10 #include "Config.h"
  11 #include "SourceCode.h"
  12 #include "refactor/Tweak.h"
  13 #include "support/Logger.h"
  14 #include "clang/AST/Decl.h"
  15 #include "clang/AST/Expr.h"
  16 #include "clang/AST/NestedNameSpecifier.h"
  17 #include "clang/AST/RecursiveASTVisitor.h"
  18 #include "clang/AST/Type.h"
  19 #include "clang/AST/TypeLoc.h"
  20 #include "clang/Basic/LLVM.h"
  21 #include "clang/Basic/SourceLocation.h"
  22 #include "clang/Tooling/Core/Replacement.h"
  23 #include "clang/Tooling/Syntax/Tokens.h"
  24 #include "llvm/ADT/StringRef.h"
  25 #include "llvm/Support/FormatVariadic.h"
  26 #include "llvm/Support/raw_ostream.h"
  27 #include <string>
  28 #include <tuple>
  29 #include <utility>
  30
  31 namespace clang {
  32 namespace clangd {
  33 namespace {
  34
  35 // Tweak for removing full namespace qualifier under cursor on DeclRefExpr and
  36 // types and adding "using" statement instead.
  37 //
  38 // Only qualifiers that refer exclusively to namespaces (no record types) are
  39 // supported. There is some guessing of appropriate place to insert the using
  40 // declaration. If we find any existing usings, we insert it there. If not, we
  41 // insert right after the inner-most relevant namespace declaration. If there is
  42 // none, or there is, but it was declared via macro, we insert above the first
  43 // top level decl.
  44 //
  45 // Currently this only removes qualifier from under the cursor. In the future,
  46 // we should improve this to remove qualifier from all occurrences of this
  47 // symbol.
  48 class AddUsing : public Tweak {
  49 public:
  50   const char *id() const override;
  51
  52   bool prepare(const Selection &Inputs) override;
  53   Expected<Effect> apply(const Selection &Inputs) override;
  54   std::string title() const override;
  55   llvm::StringLiteral kind() const override {
  56     return CodeAction::REFACTOR_KIND;
  57   }
  58
  59 private:
  60   // All of the following are set by prepare().
  61   // The qualifier to remove.
  62   NestedNameSpecifierLoc QualifierToRemove;
  63   // Qualified name to use when spelling the using declaration. This might be
  64   // different than SpelledQualifier in presence of error correction.
  65   std::string QualifierToSpell;
  66   // The name and qualifier as spelled in the code.
  67   llvm::StringRef SpelledQualifier;
  68   llvm::StringRef SpelledName;
  69   // If valid, the insertion point for "using" statement must come after this.
  70   // This is relevant when the type is defined in the main file, to make sure
  71   // the type/function is already defined at the point where "using" is added.
  72   SourceLocation MustInsertAfterLoc;
  73 };
  74 REGISTER_TWEAK(AddUsing)
  75
  76 std::string AddUsing::title() const {
  77   return std::string(llvm::formatv(
  78       "Add using-declaration for {0} and remove qualifier", SpelledName));
  79 }
  80
  81 // Locates all "using" statements relevant to SelectionDeclContext.
  82 class UsingFinder : public RecursiveASTVisitor<UsingFinder> {
  83 public:
  84   UsingFinder(std::vector<const UsingDecl *> &Results,
  85               const DeclContext *SelectionDeclContext, const SourceManager &SM)
  86       : Results(Results), SelectionDeclContext(SelectionDeclContext), SM(SM) {}
  87
  88   bool VisitUsingDecl(UsingDecl *D) {
  89     auto Loc = D->getUsingLoc();
  90     if (SM.getFileID(Loc) != SM.getMainFileID()) {
  91       return true;
  92     }
  93     if (D->getDeclContext()->Encloses(SelectionDeclContext)) {
  94       Results.push_back(D);
  95     }
  96     return true;
  97   }
  98
  99   bool TraverseDecl(Decl *Node) {
 100     if (!Node)
 101       return true;
 102     // There is no need to go deeper into nodes that do not enclose selection,
 103     // since "using" there will not affect selection, nor would it make a good
 104     // insertion point.
 105     if (!Node->getDeclContext() ||
 106         Node->getDeclContext()->Encloses(SelectionDeclContext)) {
 107       return RecursiveASTVisitor<UsingFinder>::TraverseDecl(Node);
 108     }
 109     return true;
 110   }
 111
 112 private:
 113   std::vector<const UsingDecl *> &Results;
 114   const DeclContext *SelectionDeclContext;
 115   const SourceManager &SM;
 116 };
 117
 118 bool isFullyQualified(const NestedNameSpecifier *NNS) {
 119   if (!NNS)
 120     return false;
 121   return NNS->getKind() == NestedNameSpecifier::Global ||
 122          isFullyQualified(NNS->getPrefix());
 123 }
 124
 125 struct InsertionPointData {
 126   // Location to insert the "using" statement. If invalid then the statement
 127   // should not be inserted at all (it already exists).
 128   SourceLocation Loc;
 129   // Extra suffix to place after the "using" statement. Depending on what the
 130   // insertion point is anchored to, we may need one or more \n to ensure
 131   // proper formatting.
 132   std::string Suffix;
 133   // Whether using should be fully qualified, even if what the user typed was
 134   // not. This is based on our detection of the local style.
 135   bool AlwaysFullyQualify = false;
 136 };
 137
 138 // Finds the best place to insert the "using" statement. Returns invalid
 139 // SourceLocation if the "using" statement already exists.
 140 //
 141 // The insertion point might be a little awkward if the decl we're anchoring to
 142 // has a comment in an unfortunate place (e.g. directly above function or using
 143 // decl, or immediately following "namespace {". We should add some helpers for
 144 // dealing with that and use them in other code modifications as well.
 145 llvm::Expected<InsertionPointData>
 146 findInsertionPoint(const Tweak::Selection &Inputs,
 147                    const NestedNameSpecifierLoc &QualifierToRemove,
 148                    const llvm::StringRef Name,
 149                    const SourceLocation MustInsertAfterLoc) {
 150   auto &SM = Inputs.AST->getSourceManager();
 151
 152   // Search for all using decls that affect this point in file. We need this for
 153   // two reasons: to skip adding "using" if one already exists and to find best
 154   // place to add it, if it doesn't exist.
 155   SourceLocation LastUsingLoc;
 156   std::vector<const UsingDecl *> Usings;
 157   UsingFinder(Usings, &Inputs.ASTSelection.commonAncestor()->getDeclContext(),
 158               SM)
 159       .TraverseAST(Inputs.AST->getASTContext());
 160
 161   auto IsValidPoint = [&](const SourceLocation Loc) {
 162     return MustInsertAfterLoc.isInvalid() ||
 163            SM.isBeforeInTranslationUnit(MustInsertAfterLoc, Loc);
 164   };
 165
 166   bool AlwaysFullyQualify = true;
 167   for (auto &U : Usings) {
 168     // Only "upgrade" to fully qualified is all relevant using decls are fully
 169     // qualified. Otherwise trust what the user typed.
 170     if (!isFullyQualified(U->getQualifier()))
 171       AlwaysFullyQualify = false;
 172
 173     if (SM.isBeforeInTranslationUnit(Inputs.Cursor, U->getUsingLoc()))
 174       // "Usings" is sorted, so we're done.
 175       break;
 176     if (const auto *Namespace = U->getQualifier()->getAsNamespace()) {
 177       if (Namespace->getCanonicalDecl() ==
 178               QualifierToRemove.getNestedNameSpecifier()
 179                   ->getAsNamespace()
 180                   ->getCanonicalDecl() &&
 181           U->getName() == Name) {
 182         return InsertionPointData();
 183       }
 184     }
 185
 186     // Insertion point will be before last UsingDecl that affects cursor
 187     // position. For most cases this should stick with the local convention of
 188     // add using inside or outside namespace.
 189     LastUsingLoc = U->getUsingLoc();
 190   }
 191   if (LastUsingLoc.isValid() && IsValidPoint(LastUsingLoc)) {
 192     InsertionPointData Out;
 193     Out.Loc = LastUsingLoc;
 194     Out.AlwaysFullyQualify = AlwaysFullyQualify;
 195     return Out;
 196   }
 197
 198   // No relevant "using" statements. Try the nearest namespace level.
 199   const DeclContext *ParentDeclCtx =
 200       &Inputs.ASTSelection.commonAncestor()->getDeclContext();
 201   while (ParentDeclCtx && !ParentDeclCtx->isFileContext()) {
 202     ParentDeclCtx = ParentDeclCtx->getLexicalParent();
 203   }
 204   if (auto *ND = llvm::dyn_cast_or_null<NamespaceDecl>(ParentDeclCtx)) {
 205     auto Toks = Inputs.AST->getTokens().expandedTokens(ND->getSourceRange());
 206     const auto *Tok = llvm::find_if(Toks, [](const syntax::Token &Tok) {
 207       return Tok.kind() == tok::l_brace;
 208     });
 209     if (Tok == Toks.end() || Tok->endLocation().isInvalid()) {
 210       return error("Namespace with no {{");
 211     }
 212     if (!Tok->endLocation().isMacroID() && IsValidPoint(Tok->endLocation())) {
 213       InsertionPointData Out;
 214       Out.Loc = Tok->endLocation();
 215       Out.Suffix = "\n";
 216       return Out;
 217     }
 218   }
 219   // No using, no namespace, no idea where to insert. Try above the first
 220   // top level decl after MustInsertAfterLoc.
 221   auto TLDs = Inputs.AST->getLocalTopLevelDecls();
 222   for (const auto &TLD : TLDs) {
 223     if (!IsValidPoint(TLD->getBeginLoc()))
 224       continue;
 225     InsertionPointData Out;
 226     Out.Loc = SM.getExpansionLoc(TLD->getBeginLoc());
 227     Out.Suffix = "\n\n";
 228     return Out;
 229   }
 230   return error("Cannot find place to insert \"using\"");
 231 }
 232
 233 bool isNamespaceForbidden(const Tweak::Selection &Inputs,
 234                           const NestedNameSpecifier &Namespace) {
 235   std::string NamespaceStr = printNamespaceScope(*Namespace.getAsNamespace());
 236
 237   for (StringRef Banned : Config::current().Style.FullyQualifiedNamespaces) {
 238     StringRef PrefixMatch = NamespaceStr;
 239     if (PrefixMatch.consume_front(Banned) && PrefixMatch.consume_front("::"))
 240       return true;
 241   }
 242
 243   return false;
 244 }
 245
 246 std::string getNNSLAsString(NestedNameSpecifierLoc &NNSL,
 247                             const PrintingPolicy &Policy) {
 248   std::string Out;
 249   llvm::raw_string_ostream OutStream(Out);
 250   NNSL.getNestedNameSpecifier()->print(OutStream, Policy);
 251   return OutStream.str();
 252 }
 253
 254 bool AddUsing::prepare(const Selection &Inputs) {
 255   auto &SM = Inputs.AST->getSourceManager();
 256   const auto &TB = Inputs.AST->getTokens();
 257
 258   // Do not suggest "using" in header files. That way madness lies.
 259   if (isHeaderFile(SM.getFileEntryRefForID(SM.getMainFileID())->getName(),
 260                    Inputs.AST->getLangOpts()))
 261     return false;
 262
 263   auto *Node = Inputs.ASTSelection.commonAncestor();
 264   if (Node == nullptr)
 265     return false;
 266
 267   // If we're looking at a type or NestedNameSpecifier, walk up the tree until
 268   // we find the "main" node we care about, which would be ElaboratedTypeLoc or
 269   // DeclRefExpr.
 270   for (; Node->Parent; Node = Node->Parent) {
 271     if (Node->ASTNode.get<NestedNameSpecifierLoc>()) {
 272       continue;
 273     }
 274     if (auto *T = Node->ASTNode.get<TypeLoc>()) {
 275       if (T->getAs<ElaboratedTypeLoc>()) {
 276         break;
 277       }
 278       if (Node->Parent->ASTNode.get<TypeLoc>() ||
 279           Node->Parent->ASTNode.get<NestedNameSpecifierLoc>()) {
 280         // Node is TypeLoc, but it's parent is either TypeLoc or
 281         // NestedNameSpecifier. In both cases, we want to go up, to find
 282         // the outermost TypeLoc.
 283         continue;
 284       }
 285     }
 286     break;
 287   }
 288   if (Node == nullptr)
 289     return false;
 290
 291   // Closed range for the fully qualified name as spelled in source code.
 292   SourceRange SpelledNameRange;
 293   if (auto *D = Node->ASTNode.get<DeclRefExpr>()) {
 294     if (D->getDecl()->getIdentifier()) {
 295       QualifierToRemove = D->getQualifierLoc();
 296       // Use the name range rather than expr, as the latter can contain template
 297       // arguments in the range.
 298       SpelledNameRange = D->getSourceRange();
 299       // Remove the template arguments from the name, as they shouldn't be
 300       // spelled in the using declaration.
 301       if (auto AngleLoc = D->getLAngleLoc(); AngleLoc.isValid())
 302         SpelledNameRange.setEnd(AngleLoc.getLocWithOffset(-1));
 303       MustInsertAfterLoc = D->getDecl()->getBeginLoc();
 304     }
 305   } else if (auto *T = Node->ASTNode.get<TypeLoc>()) {
 306     if (auto E = T->getAs<ElaboratedTypeLoc>()) {
 307       QualifierToRemove = E.getQualifierLoc();
 308
 309       SpelledNameRange = E.getSourceRange();
 310       if (auto T = E.getNamedTypeLoc().getAs<TemplateSpecializationTypeLoc>()) {
 311         // Remove the template arguments from the name.
 312         SpelledNameRange.setEnd(T.getLAngleLoc().getLocWithOffset(-1));
 313       }
 314
 315       if (const auto *ET = E.getTypePtr()) {
 316         if (const auto *TDT =
 317                 dyn_cast<TypedefType>(ET->getNamedType().getTypePtr())) {
 318           MustInsertAfterLoc = TDT->getDecl()->getBeginLoc();
 319         } else if (auto *TD = ET->getAsTagDecl()) {
 320           MustInsertAfterLoc = TD->getBeginLoc();
 321         }
 322       }
 323     }
 324   }
 325   if (!QualifierToRemove ||
 326       // FIXME: This only supports removing qualifiers that are made up of just
 327       // namespace names. If qualifier contains a type, we could take the
 328       // longest namespace prefix and remove that.
 329       !QualifierToRemove.getNestedNameSpecifier()->getAsNamespace() ||
 330       // Respect user config.
 331       isNamespaceForbidden(Inputs, *QualifierToRemove.getNestedNameSpecifier()))
 332     return false;
 333   // Macros are difficult. We only want to offer code action when what's spelled
 334   // under the cursor is a namespace qualifier. If it's a macro that expands to
 335   // a qualifier, user would not know what code action will actually change.
 336   // On the other hand, if the qualifier is part of the macro argument, we
 337   // should still support that.
 338   if (SM.isMacroBodyExpansion(QualifierToRemove.getBeginLoc()) ||
 339       !SM.isWrittenInSameFile(QualifierToRemove.getBeginLoc(),
 340                               QualifierToRemove.getEndLoc())) {
 341     return false;
 342   }
 343
 344   auto SpelledTokens =
 345       TB.spelledForExpanded(TB.expandedTokens(SpelledNameRange));
 346   if (!SpelledTokens)
 347     return false;
 348   auto SpelledRange =
 349       syntax::Token::range(SM, SpelledTokens->front(), SpelledTokens->back());
 350   // We only drop qualifiers that're namespaces, so this is safe.
 351   std::tie(SpelledQualifier, SpelledName) =
 352       splitQualifiedName(SpelledRange.text(SM));
 353   QualifierToSpell = getNNSLAsString(
 354       QualifierToRemove, Inputs.AST->getASTContext().getPrintingPolicy());
 355   if (!llvm::StringRef(QualifierToSpell).ends_with(SpelledQualifier) ||
 356       SpelledName.empty())
 357     return false; // What's spelled doesn't match the qualifier.
 358   return true;
 359 }
 360
 361 Expected<Tweak::Effect> AddUsing::apply(const Selection &Inputs) {
 362   auto &SM = Inputs.AST->getSourceManager();
 363
 364   tooling::Replacements R;
 365   if (auto Err = R.add(tooling::Replacement(
 366           SM, SM.getSpellingLoc(QualifierToRemove.getBeginLoc()),
 367           SpelledQualifier.size(), ""))) {
 368     return std::move(Err);
 369   }
 370
 371   auto InsertionPoint = findInsertionPoint(Inputs, QualifierToRemove,
 372                                            SpelledName, MustInsertAfterLoc);
 373   if (!InsertionPoint) {
 374     return InsertionPoint.takeError();
 375   }
 376
 377   if (InsertionPoint->Loc.isValid()) {
 378     // Add the using statement at appropriate location.
 379     std::string UsingText;
 380     llvm::raw_string_ostream UsingTextStream(UsingText);
 381     UsingTextStream << "using ";
 382     if (InsertionPoint->AlwaysFullyQualify &&
 383         !isFullyQualified(QualifierToRemove.getNestedNameSpecifier()))
 384       UsingTextStream << "::";
 385     UsingTextStream << QualifierToSpell << SpelledName << ";"
 386                     << InsertionPoint->Suffix;
 387
 388     assert(SM.getFileID(InsertionPoint->Loc) == SM.getMainFileID());
 389     if (auto Err = R.add(tooling::Replacement(SM, InsertionPoint->Loc, 0,
 390                                               UsingTextStream.str()))) {
 391       return std::move(Err);
 392     }
 393   }
 394
 395   return Effect::mainFileEdit(Inputs.AST->getASTContext().getSourceManager(),
 396                               std::move(R));
 397 }
 398
 399 } // namespace
 400 } // namespace clangd
 401 } // namespace clang