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

   1 //===--- SwapIfBranches.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 #include "ParsedAST.h"
   9 #include "SourceCode.h"
  10 #include "refactor/Tweak.h"
  11 #include "support/Logger.h"
  12 #include "clang/AST/ASTContext.h"
  13 #include "clang/AST/Stmt.h"
  14 #include "clang/Basic/LangOptions.h"
  15 #include "clang/Basic/SourceLocation.h"
  16 #include "clang/Basic/SourceManager.h"
  17 #include "clang/Tooling/Core/Replacement.h"
  18 #include "llvm/ADT/Optional.h"
  19 #include "llvm/ADT/StringRef.h"
  20 #include "llvm/Support/Casting.h"
  21 #include "llvm/Support/Error.h"
  22
  23 namespace clang {
  24 namespace clangd {
  25 namespace {
  26 /// Swaps the 'then' and 'else' branch of the if statement.
  27 /// Before:
  28 ///   if (foo) { return 10; } else { continue; }
  29 ///   ^^^^^^^                 ^^^^
  30 /// After:
  31 ///   if (foo) { continue; } else { return 10; }
  32 class SwapIfBranches : public Tweak {
  33 public:
  34   const char *id() const final;
  35
  36   bool prepare(const Selection &Inputs) override;
  37   Expected<Effect> apply(const Selection &Inputs) override;
  38   std::string title() const override { return "Swap if branches"; }
  39   llvm::StringLiteral kind() const override {
  40     return CodeAction::REFACTOR_KIND;
  41   }
  42   bool hidden() const override { return true; }
  43
  44 private:
  45   const IfStmt *If = nullptr;
  46 };
  47
  48 REGISTER_TWEAK(SwapIfBranches)
  49
  50 bool SwapIfBranches::prepare(const Selection &Inputs) {
  51   for (const SelectionTree::Node *N = Inputs.ASTSelection.commonAncestor();
  52        N && !If; N = N->Parent) {
  53     // Stop once we hit a block, e.g. a lambda in the if condition.
  54     if (llvm::isa_and_nonnull<CompoundStmt>(N->ASTNode.get<Stmt>()))
  55       return false;
  56     If = dyn_cast_or_null<IfStmt>(N->ASTNode.get<Stmt>());
  57   }
  58   // avoid dealing with single-statement brances, they require careful handling
  59   // to avoid changing semantics of the code (i.e. dangling else).
  60   return If && isa_and_nonnull<CompoundStmt>(If->getThen()) &&
  61          isa_and_nonnull<CompoundStmt>(If->getElse());
  62 }
  63
  64 Expected<Tweak::Effect> SwapIfBranches::apply(const Selection &Inputs) {
  65   auto &Ctx = Inputs.AST->getASTContext();
  66   auto &SrcMgr = Inputs.AST->getSourceManager();
  67
  68   auto ThenRng = toHalfOpenFileRange(SrcMgr, Ctx.getLangOpts(),
  69                                      If->getThen()->getSourceRange());
  70   if (!ThenRng)
  71     return error("Could not obtain range of the 'then' branch. Macros?");
  72   auto ElseRng = toHalfOpenFileRange(SrcMgr, Ctx.getLangOpts(),
  73                                      If->getElse()->getSourceRange());
  74   if (!ElseRng)
  75     return error("Could not obtain range of the 'else' branch. Macros?");
  76
  77   auto ThenCode = toSourceCode(SrcMgr, *ThenRng);
  78   auto ElseCode = toSourceCode(SrcMgr, *ElseRng);
  79
  80   tooling::Replacements Result;
  81   if (auto Err = Result.add(tooling::Replacement(Ctx.getSourceManager(),
  82                                                  ThenRng->getBegin(),
  83                                                  ThenCode.size(), ElseCode)))
  84     return std::move(Err);
  85   if (auto Err = Result.add(tooling::Replacement(Ctx.getSourceManager(),
  86                                                  ElseRng->getBegin(),
  87                                                  ElseCode.size(), ThenCode)))
  88     return std::move(Err);
  89   return Effect::mainFileEdit(SrcMgr, std::move(Result));
  90 }
  91
  92 } // namespace
  93 } // namespace clangd
  94 } // namespace clang