[VirtualFileSystem] Support virtual working directory in the RedirectingFS

Before this patch, changing the working directory of the RedirectingFS
would just forward to its external file system. This prevented us from
having a working directory that only existed in the VFS mapping.

This patch adds support for a virtual working directory in the
RedirectingFileSystem. It now keeps track of its own WD in addition to
updating the WD of the external file system. This ensures that we can
still fall through for relative paths.

This change was originally motivated by the reproducer infrastructure in
LLDB where we want to deal transparently with relative paths.

Differential revision: https://reviews.llvm.org/D65677

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@374917 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/VirtualFileSystem.h

@@ -647,9 +647,19 @@ private:
   friend class VFSFromYamlDirIterImpl;
   friend class RedirectingFileSystemParser;
 
+  bool shouldUseExternalFS() const {
+    return ExternalFSValidWD && IsFallthrough;
+  }
+
   /// The root(s) of the virtual file system.
   std::vector<std::unique_ptr<Entry>> Roots;
 
+  /// The current working directory of the file system.
+  std::string WorkingDirectory;
+
+  /// Whether the current working directory is valid for the external FS.
+  bool ExternalFSValidWD = false;
+
   /// The file system to use for external references.
   IntrusiveRefCntPtr<FileSystem> ExternalFS;
 
@@ -689,8 +699,7 @@ private:
       true;
 #endif
 
-  RedirectingFileSystem(IntrusiveRefCntPtr<FileSystem> ExternalFS)
-      : ExternalFS(std::move(ExternalFS)) {}
+  RedirectingFileSystem(IntrusiveRefCntPtr<FileSystem> ExternalFS);
 
   /// Looks up the path <tt>[Start, End)</tt> in \p From, possibly
   /// recursing into the contents of \p From if it is a directory.

lib/Support/VirtualFileSystem.cpp

@@ -989,6 +989,16 @@ std::error_code InMemoryFileSystem::isLocal(const Twine &Path, bool &Result) {
 // RedirectingFileSystem implementation
 //===-----------------------------------------------------------------------===/
 
+RedirectingFileSystem::RedirectingFileSystem(IntrusiveRefCntPtr<FileSystem> FS)
+    : ExternalFS(std::move(FS)) {
+  if (ExternalFS)
+    if (auto ExternalWorkingDirectory =
+            ExternalFS->getCurrentWorkingDirectory()) {
+      WorkingDirectory = *ExternalWorkingDirectory;
+      ExternalFSValidWD = true;
+    }
+}
+
 // FIXME: reuse implementation common with OverlayFSDirIterImpl as these
 // iterators are conceptually similar.
 class llvm::vfs::VFSFromYamlDirIterImpl
@@ -1035,12 +1045,27 @@ public:
 
 llvm::ErrorOr<std::string>
 RedirectingFileSystem::getCurrentWorkingDirectory() const {
-  return ExternalFS->getCurrentWorkingDirectory();
+  return WorkingDirectory;
 }
 
 std::error_code
 RedirectingFileSystem::setCurrentWorkingDirectory(const Twine &Path) {
-  return ExternalFS->setCurrentWorkingDirectory(Path);
+  // Don't change the working directory if the path doesn't exist.
+  if (!exists(Path))
+    return errc::no_such_file_or_directory;
+
+  // Always change the external FS but ignore its result.
+  if (ExternalFS) {
+    auto EC = ExternalFS->setCurrentWorkingDirectory(Path);
+    ExternalFSValidWD = !static_cast<bool>(EC);
+  }
+
+  SmallString<128> AbsolutePath;
+  Path.toVector(AbsolutePath);
+  if (std::error_code EC = makeAbsolute(AbsolutePath))
+    return EC;
+  WorkingDirectory = AbsolutePath.str();
+  return {};
 }
 
 std::error_code RedirectingFileSystem::isLocal(const Twine &Path,
@@ -1053,7 +1078,7 @@ directory_iterator RedirectingFileSystem::dir_begin(const Twine &Dir,
   ErrorOr<RedirectingFileSystem::Entry *> E = lookupPath(Dir);
   if (!E) {
     EC = E.getError();
-    if (IsFallthrough && EC == errc::no_such_file_or_directory)
+    if (shouldUseExternalFS() && EC == errc::no_such_file_or_directory)
       return ExternalFS->dir_begin(Dir, EC);
     return {};
   }
@@ -1071,7 +1096,7 @@ directory_iterator RedirectingFileSystem::dir_begin(const Twine &Dir,
   auto *D = cast<RedirectingFileSystem::RedirectingDirectoryEntry>(*E);
   return directory_iterator(std::make_shared<VFSFromYamlDirIterImpl>(
       Dir, D->contents_begin(), D->contents_end(),
-      /*IterateExternalFS=*/IsFallthrough, *ExternalFS, EC));
+      /*IterateExternalFS=*/shouldUseExternalFS(), *ExternalFS, EC));
 }
 
 void RedirectingFileSystem::setExternalContentsPrefixDir(StringRef PrefixDir) {
@@ -1572,7 +1597,7 @@ RedirectingFileSystem::create(std::unique_ptr<MemoryBuffer> Buffer,
   RedirectingFileSystemParser P(Stream);
 
   std::unique_ptr<RedirectingFileSystem> FS(
-      new RedirectingFileSystem(std::move(ExternalFS)));
+      new RedirectingFileSystem(ExternalFS));
 
   if (!YAMLFilePath.empty()) {
     // Use the YAML path from -ivfsoverlay to compute the dir to be prefixed
@@ -1701,7 +1726,7 @@ ErrorOr<Status> RedirectingFileSystem::status(const Twine &Path,
 ErrorOr<Status> RedirectingFileSystem::status(const Twine &Path) {
   ErrorOr<RedirectingFileSystem::Entry *> Result = lookupPath(Path);
   if (!Result) {
-    if (IsFallthrough &&
+    if (shouldUseExternalFS() &&
         Result.getError() == llvm::errc::no_such_file_or_directory) {
       return ExternalFS->status(Path);
     }
@@ -1739,7 +1764,7 @@ ErrorOr<std::unique_ptr<File>>
 RedirectingFileSystem::openFileForRead(const Twine &Path) {
   ErrorOr<RedirectingFileSystem::Entry *> E = lookupPath(Path);
   if (!E) {
-    if (IsFallthrough &&
+    if (shouldUseExternalFS() &
         E.getError() == llvm::errc::no_such_file_or_directory) {
       return ExternalFS->openFileForRead(Path);
     }
@@ -1770,7 +1795,7 @@ RedirectingFileSystem::getRealPath(const Twine &Path,
                                    SmallVectorImpl<char> &Output) const {
   ErrorOr<RedirectingFileSystem::Entry *> Result = lookupPath(Path);
   if (!Result) {
-    if (IsFallthrough &&
+    if (shouldUseExternalFS() &&
         Result.getError() == llvm::errc::no_such_file_or_directory) {
       return ExternalFS->getRealPath(Path, Output);
     }
@@ -1783,8 +1808,8 @@ RedirectingFileSystem::getRealPath(const Twine &Path,
   }
   // Even if there is a directory entry, fall back to ExternalFS if allowed,
   // because directories don't have a single external contents path.
-  return IsFallthrough ? ExternalFS->getRealPath(Path, Output)
-                       : llvm::errc::invalid_argument;
+  return shouldUseExternalFS() ? ExternalFS->getRealPath(Path, Output)
+                               : llvm::errc::invalid_argument;
 }
 
 IntrusiveRefCntPtr<FileSystem>

unittests/Support/VirtualFileSystemTest.cpp

@@ -41,7 +41,9 @@ struct DummyFile : public vfs::File {
 class DummyFileSystem : public vfs::FileSystem {
   int FSID;   // used to produce UniqueIDs
   int FileID; // used to produce UniqueIDs
+  std::string WorkingDirectory;
   std::map<std::string, vfs::Status> FilesAndDirs;
+  typedef std::map<std::string, vfs::Status>::const_iterator const_iterator;
 
   static int getNextFSID() {
     static int Count = 0;
@@ -52,8 +54,7 @@ public:
   DummyFileSystem() : FSID(getNextFSID()), FileID(0) {}
 
   ErrorOr<vfs::Status> status(const Twine &Path) override {
-    std::map<std::string, vfs::Status>::iterator I =
-        FilesAndDirs.find(Path.str());
+    auto I = findEntry(Path);
     if (I == FilesAndDirs.end())
       return make_error_code(llvm::errc::no_such_file_or_directory);
     return I->second;
@@ -66,15 +67,16 @@ public:
     return S.getError();
   }
   llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override {
-    return std::string();
+    return WorkingDirectory;
   }
   std::error_code setCurrentWorkingDirectory(const Twine &Path) override {
+    WorkingDirectory = Path.str();
     return std::error_code();
   }
   // Map any symlink to "/symlink".
   std::error_code getRealPath(const Twine &Path,
                               SmallVectorImpl<char> &Output) const override {
-    auto I = FilesAndDirs.find(Path.str());
+    auto I = findEntry(Path);
     if (I == FilesAndDirs.end())
       return make_error_code(llvm::errc::no_such_file_or_directory);
     if (I->second.isSymlink()) {
@@ -136,6 +138,14 @@ public:
     FilesAndDirs[Path] = Status;
   }
 
+  const_iterator findEntry(const Twine &Path) const {
+    SmallString<128> P;
+    Path.toVector(P);
+    std::error_code EC = makeAbsolute(P);
+    assert(!EC);
+    return FilesAndDirs.find(P.str());
+  }
+
   void addRegularFile(StringRef Path, sys::fs::perms Perms = sys::fs::all_all) {
     vfs::Status S(Path, UniqueID(FSID, FileID++),
                   std::chrono::system_clock::now(), 0, 0, 1024,
@@ -158,6 +168,12 @@ public:
   }
 };
 
+class ErrorDummyFileSystem : public DummyFileSystem {
+  std::error_code setCurrentWorkingDirectory(const Twine &Path) override {
+    return llvm::errc::no_such_file_or_directory;
+  }
+};
+
 /// Replace back-slashes by front-slashes.
 std::string getPosixPath(std::string S) {
   SmallString<128> Result;
@@ -1994,3 +2010,154 @@ TEST_F(VFSFromYAMLTest, GetRealPath) {
   EXPECT_EQ(FS->getRealPath("/non_existing", RealPath),
             errc::no_such_file_or_directory);
 }
+
+TEST_F(VFSFromYAMLTest, WorkingDirectory) {
+  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
+  Lower->addDirectory("//root/");
+  Lower->addDirectory("//root/foo");
+  Lower->addRegularFile("//root/foo/a");
+  Lower->addRegularFile("//root/foo/b");
+  IntrusiveRefCntPtr<vfs::FileSystem> FS = getFromYAMLString(
+      "{ 'use-external-names': false,\n"
+      "  'roots': [\n"
+      "{\n"
+      "  'type': 'directory',\n"
+      "  'name': '//root/',\n"
+      "  'contents': [ {\n"
+      "                  'type': 'file',\n"
+      "                  'name': 'bar/a',\n"
+      "                  'external-contents': '//root/foo/a'\n"
+      "                }\n"
+      "              ]\n"
+      "}\n"
+      "]\n"
+      "}",
+      Lower);
+  ASSERT_TRUE(FS.get() != nullptr);
+  std::error_code EC = FS->setCurrentWorkingDirectory("//root/bar/");
+  ASSERT_FALSE(EC);
+
+  llvm::ErrorOr<std::string> WorkingDir = FS->getCurrentWorkingDirectory();
+  ASSERT_TRUE(WorkingDir);
+  EXPECT_EQ(*WorkingDir, "//root/bar/");
+
+  llvm::ErrorOr<vfs::Status> Status = FS->status("./a");
+  ASSERT_FALSE(Status.getError());
+  EXPECT_TRUE(Status->isStatusKnown());
+  EXPECT_FALSE(Status->isDirectory());
+  EXPECT_TRUE(Status->isRegularFile());
+  EXPECT_FALSE(Status->isSymlink());
+  EXPECT_FALSE(Status->isOther());
+  EXPECT_TRUE(Status->exists());
+
+  EC = FS->setCurrentWorkingDirectory("bogus");
+  ASSERT_TRUE(EC);
+  WorkingDir = FS->getCurrentWorkingDirectory();
+  ASSERT_TRUE(WorkingDir);
+  EXPECT_EQ(*WorkingDir, "//root/bar/");
+
+  EC = FS->setCurrentWorkingDirectory("//root/");
+  ASSERT_FALSE(EC);
+  WorkingDir = FS->getCurrentWorkingDirectory();
+  ASSERT_TRUE(WorkingDir);
+  EXPECT_EQ(*WorkingDir, "//root/");
+
+  EC = FS->setCurrentWorkingDirectory("bar/");
+  ASSERT_FALSE(EC);
+  WorkingDir = FS->getCurrentWorkingDirectory();
+  ASSERT_TRUE(WorkingDir);
+  EXPECT_EQ(*WorkingDir, "//root/bar/");
+}
+
+TEST_F(VFSFromYAMLTest, WorkingDirectoryFallthrough) {
+  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
+  Lower->addDirectory("//root/");
+  Lower->addDirectory("//root/foo");
+  Lower->addRegularFile("//root/foo/a");
+  Lower->addRegularFile("//root/foo/b");
+  Lower->addRegularFile("//root/c");
+  IntrusiveRefCntPtr<vfs::FileSystem> FS = getFromYAMLString(
+      "{ 'use-external-names': false,\n"
+      "  'roots': [\n"
+      "{\n"
+      "  'type': 'directory',\n"
+      "  'name': '//root/',\n"
+      "  'contents': [ {\n"
+      "                  'type': 'file',\n"
+      "                  'name': 'bar/a',\n"
+      "                  'external-contents': '//root/foo/a'\n"
+      "                }\n"
+      "              ]\n"
+      "}\n"
+      "]\n"
+      "}",
+      Lower);
+  ASSERT_TRUE(FS.get() != nullptr);
+  std::error_code EC = FS->setCurrentWorkingDirectory("//root/");
+  ASSERT_FALSE(EC);
+  ASSERT_TRUE(FS.get() != nullptr);
+
+  llvm::ErrorOr<vfs::Status> Status = FS->status("bar/a");
+  ASSERT_FALSE(Status.getError());
+  EXPECT_TRUE(Status->exists());
+
+  Status = FS->status("foo/a");
+  ASSERT_FALSE(Status.getError());
+  EXPECT_TRUE(Status->exists());
+
+  EC = FS->setCurrentWorkingDirectory("//root/bar/");
+  ASSERT_FALSE(EC);
+
+  Status = FS->status("./a");
+  ASSERT_FALSE(Status.getError());
+  EXPECT_TRUE(Status->exists());
+
+  Status = FS->status("./b");
+  ASSERT_TRUE(Status.getError());
+
+  Status = FS->status("./c");
+  ASSERT_TRUE(Status.getError());
+
+  EC = FS->setCurrentWorkingDirectory("//root/");
+  ASSERT_FALSE(EC);
+
+  Status = FS->status("c");
+  ASSERT_FALSE(Status.getError());
+  EXPECT_TRUE(Status->exists());
+}
+
+TEST_F(VFSFromYAMLTest, WorkingDirectoryFallthroughInvalid) {
+  IntrusiveRefCntPtr<ErrorDummyFileSystem> Lower(new ErrorDummyFileSystem());
+  Lower->addDirectory("//root/");
+  Lower->addDirectory("//root/foo");
+  Lower->addRegularFile("//root/foo/a");
+  Lower->addRegularFile("//root/foo/b");
+  Lower->addRegularFile("//root/c");
+  IntrusiveRefCntPtr<vfs::FileSystem> FS = getFromYAMLString(
+      "{ 'use-external-names': false,\n"
+      "  'roots': [\n"
+      "{\n"
+      "  'type': 'directory',\n"
+      "  'name': '//root/',\n"
+      "  'contents': [ {\n"
+      "                  'type': 'file',\n"
+      "                  'name': 'bar/a',\n"
+      "                  'external-contents': '//root/foo/a'\n"
+      "                }\n"
+      "              ]\n"
+      "}\n"
+      "]\n"
+      "}",
+      Lower);
+  ASSERT_TRUE(FS.get() != nullptr);
+  std::error_code EC = FS->setCurrentWorkingDirectory("//root/");
+  ASSERT_FALSE(EC);
+  ASSERT_TRUE(FS.get() != nullptr);
+
+  llvm::ErrorOr<vfs::Status> Status = FS->status("bar/a");
+  ASSERT_FALSE(Status.getError());
+  EXPECT_TRUE(Status->exists());
+
+  Status = FS->status("foo/a");
+  ASSERT_TRUE(Status.getError());
+}