clang-rename: add a -export-fixes option

[vmiklos]

Summary

Use case: a class is declared in a header, and defined in two
translation units. clang-rename is asked to rename a class member that's
referenced in both translation units.

Using -i is not possible, as in case the first clang-rename invocation
touches the header, the second invocation will result in compilation
errors. Using -export-fixes handles this situation, each invocation can
work on the original source, and at the end the user can apply the
replacements with clang-apply-replacements.

[klimek]

Why don't we output replacements and use clang-apply-replacements?

[vmiklos]

This version solves the problem outline in the commit message by implementing an -export-fixes commandline option, quite similar to clang-tidy's matching option.

[klimek]

lg

[vmiklos]

Something related: currently in case multiple symbols is to be renamed in the same translation unit, clang-rename has to be invoked multiple times. This is problematic from a performance point of view, in case the symbols are in common headers of a codebase (and clang-rename is invoked for each translation unit). Would a patch that allows multiple renames to be performed with one invocation be welcome? E.g. initially via the -offset + -new-name options (let's say using , as separator), but later it would be probably more friendly to allow an input YAML file that describes what symbols should be renamed to what new names.

clang-rename/tool/ClangRename.cpp

 #include "clang/Frontend/TextDiagnosticPrinter.h"
 #include "clang/Lex/Lexer.h"
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Parse/ParseAST.h"
 #include "clang/Parse/Parser.h"
 #include "clang/Rewrite/Core/Rewriter.h"
 #include "clang/Tooling/CommonOptionsParser.h"
 #include "clang/Tooling/Refactoring.h"
+#include "clang/Tooling/ReplacementsYaml.h"
 #include "clang/Tooling/Tooling.h"
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "llvm/Support/Host.h"
 #include <cstdlib>
 #include <string>
 
 using namespace llvm;
 
PrintName(
     "pn",
     cl::desc("Print the found symbol's name prior to renaming to stderr."),
     cl::cat(ClangRenameCategory));
 static cl::opt<bool>
 PrintLocations(
     "pl",
     cl::desc("Print the locations affected by renaming to stderr."),
     cl::cat(ClangRenameCategory));
+static cl::opt<std::string>
+ExportFixes(
+    "export-fixes",
+    cl::desc("YAML file to store suggested fixes in."),
+    cl::value_desc("filename"),
+    cl::cat(ClangRenameCategory));
 
 #define CLANG_RENAME_VERSION "0.0.1"
 
 static void PrintVersion() {
   outs() << "clang-rename version " << CLANG_RENAME_VERSION << "\n";
 }
 
 using namespace clang;
int main(int argc, const char **argv) {
   auto Factory = tooling::newFrontendActionFactory(&RenameAction);
   int res;
 
   if (Inplace) {
     res = Tool.runAndSave(Factory.get());
   } else {
     res = Tool.run(Factory.get());
 
+    if (!ExportFixes.empty()) {
+      std::error_code EC;
+      llvm::raw_fd_ostream OS(ExportFixes, EC, llvm::sys::fs::F_None);
+      if (EC) {
+        llvm::errs() << "Error opening output file: " << EC.message() << '\n';
+        exit(1);
+      }
+
+      // Export replacements.
+      tooling::TranslationUnitReplacements TUR;
+      const tooling::Replacements &Replacements = Tool.getReplacements();
+      TUR.Replacements.insert(TUR.Replacements.end(), Replacements.begin(),
+                              Replacements.end());
+
+      yaml::Output YAML(OS);
+      YAML << TUR;
+      OS.close();
+      exit(0);
+    }
+
     // Write every file to stdout. Right now we just barf the files without any
     // indication of which files start where, other than that we print the files
     // in the same order we see them.
     LangOptions DefaultLangOptions;
     IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts =
         new DiagnosticOptions();
     TextDiagnosticPrinter DiagnosticPrinter(errs(), &*DiagOpts);
     DiagnosticsEngine Diagnostics(

test/clang-rename/ClassTestReplacements.cpp

+// RUN: mkdir -p %T/fixes
+// RUN: cat %s > %t.cpp
+// RUN: clang-rename -offset=225 -new-name=Hector -export-fixes=%T/fixes.yaml %t.cpp --
+// RUN: clang-apply-replacements %T
+// RUN: sed 's,//.*,,' %t.cpp | FileCheck %s
+class Cla  // CHECK: class Hector
+{
+};
+
+// Use grep -FUbo 'Cla' <file> to get the correct offset of Cla when changing
+// this file.