[clangd] Add a filename parameter to FileSystemProvider.

clangd/ClangdServer.h

public:
   virtual void
   onDiagnosticsReady(PathRef File,
                      Tagged<std::vector<DiagWithFixIts>> Diagnostics) = 0;
 };
 
 class FileSystemProvider {
 public:
   virtual ~FileSystemProvider() = default;
+  /// Called by ClangdServer to obtain a vfs::FileSystem to be used for parsing.
+  /// Name of the file that will be parsed is passed in \p File.
+  ///
   /// \return A filesystem that will be used for all file accesses in clangd.
   /// A Tag returned by this method will be propagated to all results of clangd
   /// that will use this filesystem.
-  virtual Tagged<IntrusiveRefCntPtr<vfs::FileSystem>> getTaggedFileSystem() = 0;
+  virtual Tagged<IntrusiveRefCntPtr<vfs::FileSystem>>
+  getTaggedFileSystem(PathRef File) = 0;
 };
 
 class RealFileSystemProvider : public FileSystemProvider {
 public:
   /// \return getRealFileSystem() tagged with default tag, i.e. VFSTag()
-  Tagged<IntrusiveRefCntPtr<vfs::FileSystem>> getTaggedFileSystem() override;
+  Tagged<IntrusiveRefCntPtr<vfs::FileSystem>>
+  getTaggedFileSystem(PathRef File) override;
 };
 
 class ClangdServer;
 
 /// Handles running WorkerRequests of ClangdServer on a separate threads.
 /// Currently runs only one worker thread.
 class ClangdScheduler {
 public:

clangd/ClangdServer.cpp

Position clangd::offsetToPosition(StringRef Code, size_t Offset) {
   // FIXME: \r\n
   // FIXME: UTF-8
   int Lines = JustBefore.count('\n');
   int Cols = JustBefore.size() - JustBefore.rfind('\n') - 1;
   return {Lines, Cols};
 }
 
 Tagged<IntrusiveRefCntPtr<vfs::FileSystem>>
-RealFileSystemProvider::getTaggedFileSystem() {
+RealFileSystemProvider::getTaggedFileSystem(PathRef File) {
   return make_tagged(vfs::getRealFileSystem(), VFSTag());
 }
 
 ClangdScheduler::ClangdScheduler(bool RunSynchronously)
     : RunSynchronously(RunSynchronously) {
   if (RunSynchronously) {
     // Don't start the worker thread if we're running synchronously
     return;
void ClangdServer::addDocument(PathRef File, StringRef Contents) {
   Path FileStr = File;
   WorkScheduler.addToFront([this, FileStr, Version]() {
     auto FileContents = DraftMgr.getDraft(FileStr);
     if (FileContents.Version != Version)
       return; // This request is outdated, do nothing
 
     assert(FileContents.Draft &&
            "No contents inside a file that was scheduled for reparse");
-    auto TaggedFS = FSProvider.getTaggedFileSystem();
+    auto TaggedFS = FSProvider.getTaggedFileSystem(FileStr);
     Units.runOnUnit(
         FileStr, *FileContents.Draft, CDB, PCHs, TaggedFS.Value,
         [&](ClangdUnit const &Unit) {
           DiagConsumer.onDiagnosticsReady(
               FileStr, make_tagged(Unit.getLocalDiagnostics(), TaggedFS.Tag));
         });
   });
 }
if (!OverridenContents) {
     assert(FileContents.Draft &&
            "codeComplete is called for non-added document");
 
     DraftStorage = std::move(*FileContents.Draft);
     OverridenContents = DraftStorage;
   }
 
   std::vector<CompletionItem> Result;
-  auto TaggedFS = FSProvider.getTaggedFileSystem();
+  auto TaggedFS = FSProvider.getTaggedFileSystem(File);
   // It would be nice to use runOnUnitWithoutReparse here, but we can't
   // guarantee the correctness of code completion cache here if we don't do the
   // reparse.
   Units.runOnUnit(File, *OverridenContents, CDB, PCHs, TaggedFS.Value,
                   [&](ClangdUnit &Unit) {
                     Result = Unit.codeComplete(*OverridenContents, Pos,
                                                TaggedFS.Value);
                   });

unittests/clangd/ClangdTests.cpp

public:
   std::vector<tooling::CompileCommand>
   getCompileCommands(PathRef File) override {
     return {};
   }
 };
 
 class MockFSProvider : public FileSystemProvider {
 public:
-  Tagged<IntrusiveRefCntPtr<vfs::FileSystem>> getTaggedFileSystem() override {
+  Tagged<IntrusiveRefCntPtr<vfs::FileSystem>>
+  getTaggedFileSystem(PathRef File) override {
     IntrusiveRefCntPtr<vfs::InMemoryFileSystem> MemFS(
         new vfs::InMemoryFileSystem);
+    if (ExpectedFile)
+      EXPECT_EQ(*ExpectedFile, File);
+
     for (auto &FileAndContents : Files)
       MemFS->addFile(FileAndContents.first(), time_t(),
                      llvm::MemoryBuffer::getMemBuffer(FileAndContents.second,
                                                       FileAndContents.first()));
 
     auto OverlayFS = IntrusiveRefCntPtr<vfs::OverlayFileSystem>(
         new vfs::OverlayFileSystem(vfs::getTempOnlyFS()));
     OverlayFS->pushOverlay(std::move(MemFS));
     return make_tagged(OverlayFS, Tag);
   }
 
+  llvm::Optional<SmallString<32>> ExpectedFile;
   llvm::StringMap<std::string> Files;
   VFSTag Tag = VFSTag();
 };
 
 /// Replaces all patterns of the form 0x123abc with spaces
 std::string replacePtrsInDump(std::string const &Dump) {
   llvm::Regex RE("0x[0-9a-fA-F]+");
   llvm::SmallVector<StringRef, 1> Matches;
std::string parseSourceAndDumpAST(
     MockCompilationDatabase CDB;
     ClangdServer Server(CDB, DiagConsumer, FS,
                         /*RunSynchronously=*/false);
     for (const auto &FileWithContents : ExtraFiles)
       FS.Files[getVirtualTestFilePath(FileWithContents.first)] =
           FileWithContents.second;
 
     auto SourceFilename = getVirtualTestFilePath(SourceFileRelPath);
+
+    FS.ExpectedFile = SourceFilename;
     Server.addDocument(SourceFilename, SourceContents);
+
     auto Result = dumpASTWithoutMemoryLocs(Server, SourceFilename);
     EXPECT_EQ(ExpectErrors, DiagConsumer.hadErrorInLastDiags());
     return Result;
   }
 };
 
 TEST_F(ClangdVFSTest, Parse) {
   // FIXME: figure out a stable format for AST dumps, so that we can check the

 int b = a;
 )cpp";
 
   auto FooCpp = getVirtualTestFilePath("foo.cpp");
   auto FooH = getVirtualTestFilePath("foo.h");
 
   FS.Files[FooH] = "int a;";
   FS.Files[FooCpp] = SourceContents;
+  FS.ExpectedFile = FooCpp;
 
   Server.addDocument(FooCpp, SourceContents);
   auto DumpParse1 = dumpASTWithoutMemoryLocs(Server, FooCpp);
   EXPECT_FALSE(DiagConsumer.hadErrorInLastDiags());
 
   Server.addDocument(FooCpp, "");
   auto DumpParseEmpty = dumpASTWithoutMemoryLocs(Server, FooCpp);
   EXPECT_FALSE(DiagConsumer.hadErrorInLastDiags());

 int b = a;
 )cpp";
 
   auto FooCpp = getVirtualTestFilePath("foo.cpp");
   auto FooH = getVirtualTestFilePath("foo.h");
 
   FS.Files[FooH] = "int a;";
   FS.Files[FooCpp] = SourceContents;
+  FS.ExpectedFile = FooCpp;
 
   Server.addDocument(FooCpp, SourceContents);
   auto DumpParse1 = dumpASTWithoutMemoryLocs(Server, FooCpp);
   EXPECT_FALSE(DiagConsumer.hadErrorInLastDiags());
 
   FS.Files[FooH] = "";
   Server.forceReparse(FooCpp);
   auto DumpParseDifferent = dumpASTWithoutMemoryLocs(Server, FooCpp);
TEST_F(ClangdVFSTest, CheckVersions) {
   ErrorCheckingDiagConsumer DiagConsumer;
   MockCompilationDatabase CDB;
   ClangdServer Server(CDB, DiagConsumer, FS,
                       /*RunSynchronously=*/true);
 
   auto FooCpp = getVirtualTestFilePath("foo.cpp");
   const auto SourceContents = "int a;";
   FS.Files[FooCpp] = SourceContents;
-  FS.Tag = "123";
+  FS.ExpectedFile = FooCpp;
 
+  FS.Tag = "123";
   Server.addDocument(FooCpp, SourceContents);
   EXPECT_EQ(DiagConsumer.lastVFSTag(), FS.Tag);
   EXPECT_EQ(Server.codeComplete(FooCpp, Position{0, 0}).Tag, FS.Tag);
 
   FS.Tag = "321";
   Server.addDocument(FooCpp, SourceContents);
   EXPECT_EQ(DiagConsumer.lastVFSTag(), FS.Tag);
   EXPECT_EQ(Server.codeComplete(FooCpp, Position{0, 0}).Tag, FS.Tag);

 )cpp";
   // Complete after '=' sign. We need to be careful to keep the SourceContents'
   // size the same.
   // We complete on the 3rd line (2nd in zero-based numbering), because raw
   // string literal of the SourceContents starts with a newline(it's easy to
   // miss).
   Position CompletePos = {2, 8};
   FS.Files[FooCpp] = SourceContents;
+  FS.ExpectedFile = FooCpp;
 
   Server.addDocument(FooCpp, SourceContents);
 
   {
     auto CodeCompletionResults1 =
         Server.codeComplete(FooCpp, CompletePos, None).Value;
     EXPECT_TRUE(ContainsItem(CodeCompletionResults1, "aba"));
     EXPECT_FALSE(ContainsItem(CodeCompletionResults1, "cbc"));