3 files changed, 96 insertions, 1 deletions
diff --git a/clang/lib/Tooling/CMakeLists.txt b/clang/lib/Tooling/CMakeLists.txt
index 05061f0a10a..59c990daaa2 100644
--- a/clang/lib/Tooling/CMakeLists.txt
+++ b/clang/lib/Tooling/CMakeLists.txt
@@ -17,6 +17,7 @@ add_clang_library(clangTooling
   CommonOptionsParser.cpp
   CompilationDatabase.cpp
   Execution.cpp
+  ExpandResponseFilesCompilationDatabase.cpp
   FileMatchTrie.cpp
   FixIt.cpp
   GuessTargetAndModeCompilationDatabase.cpp
diff --git a/clang/lib/Tooling/ExpandResponseFilesCompilationDatabase.cpp b/clang/lib/Tooling/ExpandResponseFilesCompilationDatabase.cpp
new file mode 100644
index 00000000000..bb519277dfa
--- /dev/null
+++ b/clang/lib/Tooling/ExpandResponseFilesCompilationDatabase.cpp
@@ -0,0 +1,92 @@
+//===- ExpandResponseFileCompilationDataBase.cpp --------------------------===//
+//
+// 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/CompilationDatabase.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/ConvertUTF.h"
+#include "llvm/Support/ErrorOr.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/StringSaver.h"
+
+namespace clang {
+namespace tooling {
+namespace {
+
+class ExpandResponseFilesDatabase : public CompilationDatabase {
+public:
+  ExpandResponseFilesDatabase(
+      std::unique_ptr<CompilationDatabase> Base,
+      llvm::cl::TokenizerCallback Tokenizer,
+      llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS)
+      : Base(std::move(Base)), Tokenizer(Tokenizer), FS(std::move(FS)) {
+    assert(this->Base != nullptr);
+    assert(this->Tokenizer != nullptr);
+    assert(this->FS != nullptr);
+  }
+
+  std::vector<std::string> getAllFiles() const override {
+    return Base->getAllFiles();
+  }
+
+  std::vector<CompileCommand>
+  getCompileCommands(StringRef FilePath) const override {
+    return expand(Base->getCompileCommands(FilePath));
+  }
+
+  std::vector<CompileCommand> getAllCompileCommands() const override {
+    return expand(Base->getAllCompileCommands());
+  }
+
+private:
+  std::vector<CompileCommand> expand(std::vector<CompileCommand> Cmds) const {
+    for (auto &Cmd : Cmds) {
+      // FIXME: we should rather propagate the current directory into
+      // ExpandResponseFiles as well in addition to FS.
+      if (std::error_code EC = FS->setCurrentWorkingDirectory(Cmd.Directory)) {
+        llvm::consumeError(llvm::errorCodeToError(EC));
+        continue;
+      }
+      bool SeenRSPFile = false;
+      llvm::SmallVector<const char *, 20> Argv;
+      Argv.reserve(Cmd.CommandLine.size());
+      for (auto &Arg : Cmd.CommandLine) {
+        Argv.push_back(Arg.c_str());
+        SeenRSPFile |= Arg.front() == '@';
+      }
+      if (!SeenRSPFile)
+        continue;
+      llvm::BumpPtrAllocator Alloc;
+      llvm::StringSaver Saver(Alloc);
+      llvm::cl::ExpandResponseFiles(Saver, Tokenizer, Argv, false, false, *FS);
+      Cmd.CommandLine.assign(Argv.begin(), Argv.end());
+    }
+    return Cmds;
+  }
+
+private:
+  std::unique_ptr<CompilationDatabase> Base;
+  llvm::cl::TokenizerCallback Tokenizer;
+  llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS;
+};
+
+} // namespace
+
+std::unique_ptr<CompilationDatabase>
+expandResponseFiles(std::unique_ptr<CompilationDatabase> Base,
+                    llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS) {
+  auto Tokenizer = llvm::Triple(llvm::sys::getProcessTriple()).isOSWindows()
+                       ? llvm::cl::TokenizeWindowsCommandLine
+                       : llvm::cl::TokenizeGNUCommandLine;
+  return std::make_unique<ExpandResponseFilesDatabase>(
+      std::move(Base), Tokenizer, std::move(FS));
+}
+
+} // namespace tooling
+} // namespace clang
diff --git a/clang/lib/Tooling/JSONCompilationDatabase.cpp b/clang/lib/Tooling/JSONCompilationDatabase.cpp
index f19a0f7550b..8dd46083902 100644
--- a/clang/lib/Tooling/JSONCompilationDatabase.cpp
+++ b/clang/lib/Tooling/JSONCompilationDatabase.cpp
@@ -168,7 +168,9 @@ class JSONCompilationDatabasePlugin : public CompilationDatabasePlugin {
     auto Base = JSONCompilationDatabase::loadFromFile(
         JSONDatabasePath, ErrorMessage, JSONCommandLineSyntax::AutoDetect);
     return Base ? inferTargetAndDriverMode(
-                      inferMissingCompileCommands(std::move(Base)))
+                      inferMissingCompileCommands(expandResponseFiles(
+                          std::move(Base),
+                          llvm::vfs::createPhysicalFileSystem().release())))
                 : nullptr;
   }
 };