[LibTooling] Add Transformer, a library for source-to-source transformations.

Summary: Adds a basic version of Transformer, a library supporting the concise specification of clang-based source-to-source transformations.  A full discussion of the end goal can be found on the cfe-dev list with subject "[RFC] Easier source-to-source transformations with clang tooling".

Reviewers: ilya-biryukov

Reviewed By: ilya-biryukov

Subscribers: mgorny, jfb, jdoerfert, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D59376

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@357576 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 205 insertions, 0 deletions

diff --git a/lib/Tooling/Refactoring/CMakeLists.txt b/lib/Tooling/Refactoring/CMakeLists.txt
index 402b5d3c6a..e500283998 100644
--- a/lib/Tooling/Refactoring/CMakeLists.txt
+++ b/lib/Tooling/Refactoring/CMakeLists.txt
@@ -12,6 +12,7 @@ add_clang_library(clangToolingRefactor
   Rename/USRFinder.cpp
   Rename/USRFindingAction.cpp
   Rename/USRLocFinder.cpp
+  Transformer.cpp
 
   LINK_LIBS
   clangAST
diff --git a/lib/Tooling/Refactoring/Transformer.cpp b/lib/Tooling/Refactoring/Transformer.cpp
new file mode 100644
index 0000000000..4899dfd41f
--- /dev/null
+++ b/lib/Tooling/Refactoring/Transformer.cpp
@@ -0,0 +1,204 @@
+//===--- Transformer.cpp - Transformer library implementation ---*- C++ -*-===//
+//
+// 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 "clang/Tooling/Refactoring/Transformer.h"
+#include "clang/AST/Expr.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/SourceLocation.h"
+#include "clang/Rewrite/Core/Rewriter.h"
+#include "clang/Tooling/FixIt.h"
+#include "clang/Tooling/Refactoring.h"
+#include "clang/Tooling/Refactoring/AtomicChange.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/Error.h"
+#include <deque>
+#include <string>
+#include <utility>
+#include <vector>
+
+using namespace clang;
+using namespace tooling;
+
+using ast_matchers::MatchFinder;
+using ast_type_traits::ASTNodeKind;
+using ast_type_traits::DynTypedNode;
+using llvm::Error;
+using llvm::Expected;
+using llvm::Optional;
+using llvm::StringError;
+using llvm::StringRef;
+using llvm::Twine;
+
+using MatchResult = MatchFinder::MatchResult;
+
+// Did the text at this location originate in a macro definition (aka. body)?
+// For example,
+//
+//   #define NESTED(x) x
+//   #define MACRO(y) { int y  = NESTED(3); }
+//   if (true) MACRO(foo)
+//
+// The if statement expands to
+//
+//   if (true) { int foo = 3; }
+//                   ^     ^
+//                   Loc1  Loc2
+//
+// For SourceManager SM, SM.isMacroArgExpansion(Loc1) and
+// SM.isMacroArgExpansion(Loc2) are both true, but isOriginMacroBody(sm, Loc1)
+// is false, because "foo" originated in the source file (as an argument to a
+// macro), whereas isOriginMacroBody(SM, Loc2) is true, because "3" originated
+// in the definition of MACRO.
+static bool isOriginMacroBody(const clang::SourceManager &SM,
+                              clang::SourceLocation Loc) {
+  while (Loc.isMacroID()) {
+    if (SM.isMacroBodyExpansion(Loc))
+      return true;
+    // Otherwise, it must be in an argument, so we continue searching up the
+    // invocation stack. getImmediateMacroCallerLoc() gives the location of the
+    // argument text, inside the call text.
+    Loc = SM.getImmediateMacroCallerLoc(Loc);
+  }
+  return false;
+}
+
+static llvm::Error invalidArgumentError(Twine Message) {
+  return llvm::make_error<StringError>(llvm::errc::invalid_argument, Message);
+}
+
+static llvm::Error typeError(StringRef Id, const ASTNodeKind &Kind,
+                             Twine Message) {
+  return invalidArgumentError(
+      Message + " (node id=" + Id + " kind=" + Kind.asStringRef() + ")");
+}
+
+static llvm::Error missingPropertyError(StringRef Id, Twine Description,
+                                        StringRef Property) {
+  return invalidArgumentError(Description + " requires property '" + Property +
+                              "' (node id=" + Id + ")");
+}
+
+static Expected<CharSourceRange>
+getTargetRange(StringRef Target, const DynTypedNode &Node, ASTNodeKind Kind,
+               NodePart TargetPart, ASTContext &Context) {
+  switch (TargetPart) {
+  case NodePart::Node: {
+    // For non-expression statements, associate any trailing semicolon with the
+    // statement text.  However, if the target was intended as an expression (as
+    // indicated by its kind) then we do not associate any trailing semicolon
+    // with it.  We only associate the exact expression text.
+    if (Node.get<Stmt>() != nullptr) {
+      auto ExprKind = ASTNodeKind::getFromNodeKind<clang::Expr>();
+      if (!ExprKind.isBaseOf(Kind))
+        return fixit::getExtendedRange(Node, tok::TokenKind::semi, Context);
+    }
+    return CharSourceRange::getTokenRange(Node.getSourceRange());
+  }
+  case NodePart::Member:
+    if (auto *M = Node.get<clang::MemberExpr>())
+      return CharSourceRange::getTokenRange(
+          M->getMemberNameInfo().getSourceRange());
+    return typeError(Target, Node.getNodeKind(),
+                     "NodePart::Member applied to non-MemberExpr");
+  case NodePart::Name:
+    if (const auto *D = Node.get<clang::NamedDecl>()) {
+      if (!D->getDeclName().isIdentifier())
+        return missingPropertyError(Target, "NodePart::Name", "identifier");
+      SourceLocation L = D->getLocation();
+      auto R = CharSourceRange::getTokenRange(L, L);
+      // Verify that the range covers exactly the name.
+      // FIXME: extend this code to support cases like `operator +` or
+      // `foo<int>` for which this range will be too short.  Doing so will
+      // require subcasing `NamedDecl`, because it doesn't provide virtual
+      // access to the \c DeclarationNameInfo.
+      if (fixit::internal::getText(R, Context) != D->getName())
+        return CharSourceRange();
+      return R;
+    }
+    if (const auto *E = Node.get<clang::DeclRefExpr>()) {
+      if (!E->getNameInfo().getName().isIdentifier())
+        return missingPropertyError(Target, "NodePart::Name", "identifier");
+      SourceLocation L = E->getLocation();
+      return CharSourceRange::getTokenRange(L, L);
+    }
+    if (const auto *I = Node.get<clang::CXXCtorInitializer>()) {
+      if (!I->isMemberInitializer() && I->isWritten())
+        return missingPropertyError(Target, "NodePart::Name",
+                                    "explicit member initializer");
+      SourceLocation L = I->getMemberLocation();
+      return CharSourceRange::getTokenRange(L, L);
+    }
+    return typeError(
+        Target, Node.getNodeKind(),
+        "NodePart::Name applied to neither DeclRefExpr, NamedDecl nor "
+        "CXXCtorInitializer");
+  }
+  llvm_unreachable("Unexpected case in NodePart type.");
+}
+
+Expected<Transformation>
+tooling::applyRewriteRule(const RewriteRule &Rule,
+                          const ast_matchers::MatchFinder::MatchResult &Match) {
+  if (Match.Context->getDiagnostics().hasErrorOccurred())
+    return Transformation();
+
+  auto &NodesMap = Match.Nodes.getMap();
+  auto It = NodesMap.find(Rule.Target);
+  assert (It != NodesMap.end() && "Rule.Target must be bound in the match.");
+
+  Expected<CharSourceRange> TargetOrErr =
+      getTargetRange(Rule.Target, It->second, Rule.TargetKind, Rule.TargetPart,
+                     *Match.Context);
+  if (auto Err = TargetOrErr.takeError())
+    return std::move(Err);
+  auto &Target = *TargetOrErr;
+  if (Target.isInvalid() ||
+      isOriginMacroBody(*Match.SourceManager, Target.getBegin()))
+    return Transformation();
+
+  return Transformation{Target, Rule.Replacement(Match)};
+}
+
+constexpr llvm::StringLiteral RewriteRule::RootId;
+
+RewriteRuleBuilder RewriteRuleBuilder::replaceWith(TextGenerator T) {
+  Rule.Replacement = std::move(T);
+  return *this;
+}
+
+RewriteRuleBuilder RewriteRuleBuilder::because(TextGenerator T) {
+  Rule.Explanation = std::move(T);
+  return *this;
+}
+
+void Transformer::registerMatchers(MatchFinder *MatchFinder) {
+  MatchFinder->addDynamicMatcher(Rule.Matcher, this);
+}
+
+void Transformer::run(const MatchResult &Result) {
+  auto ChangeOrErr = applyRewriteRule(Rule, Result);
+  if (auto Err = ChangeOrErr.takeError()) {
+    llvm::errs() << "Rewrite failed: " << llvm::toString(std::move(Err))
+                 << "\n";
+    return;
+  }
+  auto &Change = *ChangeOrErr;
+  auto &Range = Change.Range;
+  if (Range.isInvalid()) {
+    // No rewrite applied (but no error encountered either).
+    return;
+  }
+  AtomicChange AC(*Result.SourceManager, Range.getBegin());
+  if (auto Err = AC.replace(*Result.SourceManager, Range, Change.Replacement))
+    AC.setError(llvm::toString(std::move(Err)));
+  Consumer(AC);
+}