Remove unneeded scoped_refptr<>::get on method bind

tools/clang/base_bind_rewriters/BaseBindRewriters.cpp

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.

[dcheng, 2016/08/29 20:04:09]

Let's document what the tool does (similar to
https://cs.chromium.org/chromium/src/tools/clang/rewrite_to_chrome_style/Rewr...,
though that's out-of-date =P)

[tzik, 2016/08/30 07:40:50]

Done.

+
+#include <assert.h>
+#include <algorithm>
+#include <memory>
+#include <string>
+
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/ASTMatchers/ASTMatchersMacros.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Frontend/FrontendActions.h"
+#include "clang/Lex/Lexer.h"
+#include "clang/Tooling/CommonOptionsParser.h"
+#include "clang/Tooling/Refactoring.h"
+#include "clang/Tooling/Tooling.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/TargetSelect.h"
+
+using namespace clang::ast_matchers;
+using clang::tooling::CommonOptionsParser;
+using Replacements = std::vector<clang::tooling::Replacement>;
+using Rewriter = std::function<std::string(const std::string&)>;
+
+namespace {
+
+class RewriterCallback : public MatchFinder::MatchCallback {
+ public:
+  RewriterCallback(Replacements* replacements, Rewriter rewriter)
+      : replacements_(replacements), rewriter_(std::move(rewriter)) {}
+
+  void run(const MatchFinder::MatchResult& result) override {
+    const clang::Expr* target = result.Nodes.getNodeAs<clang::Expr>("target");
+    assert(target && "Unexpected match! No Expr captured!");
+
+    clang::CharSourceRange range = clang::CharSourceRange::getTokenRange(
+        result.SourceManager->getSpellingLoc(target->getLocStart()),
+        result.SourceManager->getSpellingLoc(target->getLocEnd()));
+    std::string text = clang::Lexer::getSourceText(
+        range, *result.SourceManager, result.Context->getLangOpts());

[dcheng, 2016/08/29 20:04:09]

Usually it's slightly safer to not grab the source text and manipulate it (see
my comment on the std::function callback below).

In this case, we can get the MemberExpr for the CXXMemberCallExpr by using
CXXMemberCallExpr::callee().

From there, I think we can just emit a replacement to remove the source from
MemberExpr::getOperatorLoc() to CXXMemberCallExpr::getLocEnd().

[tzik, 2016/08/30 07:40:50]

Done.

+    replacements_->emplace_back(
+        *result.SourceManager, range, rewriter_(text));
+  }
+
+ private:
+  Replacements* replacements_;
+  Rewriter rewriter_;
+};
+
+llvm::cl::extrahelp common_help(CommonOptionsParser::HelpMessage);
+
+}  // namespace.
+
+int main(int argc, const char* argv[]) {
+  llvm::InitializeNativeTarget();
+  llvm::InitializeNativeTargetAsmParser();
+  llvm::cl::OptionCategory category(
+      "Remove raw pointer on the receiver of Bind() target");
+  CommonOptionsParser options(argc, argv, category);
+  clang::tooling::ClangTool tool(options.getCompilations(),
+                                 options.getSourcePathList());
+
+  MatchFinder match_finder;
+  std::vector<clang::tooling::Replacement> replacements;
+
+  auto is_bind_call = callee(namedDecl(hasName("::base::Bind")));
+  auto is_method_bind = hasArgument(0, hasType(memberPointerType()));
+  auto is_raw_pointer_receiver = hasArgument(1, hasType(pointerType()));
+  auto is_scoped_refptr_get_call =
+      cxxMemberCallExpr(thisPointerType(namedDecl(hasName("scoped_refptr"))),
+                        callee(namedDecl(hasName("get"))));
+
+  // Remove unneeded scoped_refptr<>::get on a receivers of method bind.
+  // Example:
+  //   // Before
+  //   scoped_refptr<Foo> foo;
+  //   base::Bind(&Foo::Bar, foo.get());
+  //
+  //   // After
+  //   scoped_refptr<Foo> foo;
+  //   base::Bind(&Foo::Bar, foo);
+  //
+  RewriterCallback remove_unneeded_scoped_refptr_get(
+      &replacements,
+      [](const std::string& text) {
+        return text.substr(0, text.size() - sizeof(".get()") + 1);

[dcheng, 2016/08/29 20:04:09]

Nit: strlen() should work here and hopefully make it slightly easier to read.
But this will be problematic if the code isn't formatted as expected: for
example, .get() is .get(\n) or ->get().

+      });
+  match_finder.addMatcher(
+      callExpr(is_bind_call, is_method_bind, is_raw_pointer_receiver,
+               hasArgument(1, is_scoped_refptr_get_call),
+               hasArgument(1, stmt().bind("target"))),
+      &remove_unneeded_scoped_refptr_get);
+
+  std::unique_ptr<clang::tooling::FrontendActionFactory> factory =
+      clang::tooling::newFrontendActionFactory(&match_finder);
+  int result = tool.run(factory.get());
+  if (result != 0)
+    return result;
+
+  // Serialization format is documented in tools/clang/scripts/run_tool.py
+  llvm::outs() << "==== BEGIN EDITS ====\n";
+  for (const auto& r : replacements) {
+    std::string replacement_text = r.getReplacementText().str();
+    std::replace(replacement_text.begin(), replacement_text.end(), '\n', '\0');
+    llvm::outs() << "r:::" << r.getFilePath() << ":::" << r.getOffset()
+                 << ":::" << r.getLength() << ":::" << replacement_text << "\n";
+  }
+  llvm::outs() << "==== END EDITS ====\n";
+
+  return 0;
+}