[VirtualFileSystem] Support creating directories then adding files inside

[benhamilton]

Summary

In https://reviews.llvm.org/D39572 , I added support for specifying
Type when invoking InMemoryFileSystem::addFile().

However, I didn't account for the fact that when Type is
directory_file, we need to construct an InMemoryDirectory, not an
InMemoryFile, or else clients cannot create files inside that
directory.

This diff fixes the bug and adds a test.

Test Plan: New test added. Ran test with:

% make -j12 check-clang-tools

[benhamilton]

• Update docs for addFile and addFileNoOwn

[bkramer]

lg

lib/Basic/VirtualFileSystem.cpp

535

Style: variables start with a capital letter.

[benhamilton]

• Fix style.

include/clang/Basic/VirtualFileSystem.h

class InMemoryFileSystem : public FileSystem {
   std::unique_ptr<detail::InMemoryDirectory> Root;
   std::string WorkingDirectory;
   bool UseNormalizedPaths = true;
 
 public:
   explicit InMemoryFileSystem(bool UseNormalizedPaths = true);
   ~InMemoryFileSystem() override;
 
-  /// Add a buffer to the VFS with a path. The VFS owns the buffer.
-  /// If present, User, Group, Type and Perms apply to the newly-created file.
-  /// \return true if the file was successfully added, false if the file already
-  /// exists in the file system with different contents.
+  /// Add a file containing a buffer or a directory to the VFS with a
+  /// path. The VFS owns the buffer.  If present, User, Group, Type
+  /// and Perms apply to the newly-created file or directory.
+  /// \return true if the file or directory was successfully added,
+  /// false if the file or directory already exists in the file system with
+  /// different contents.
   bool addFile(const Twine &Path, time_t ModificationTime,
                std::unique_ptr<llvm::MemoryBuffer> Buffer,
                Optional<uint32_t> User = None, Optional<uint32_t> Group = None,
                Optional<llvm::sys::fs::file_type> Type = None,
                Optional<llvm::sys::fs::perms> Perms = None);
   /// Add a buffer to the VFS with a path. The VFS does not own the buffer.
-  /// If present, User, Group, Type and Perms apply to the newly-created file.
-  /// \return true if the file was successfully added, false if the file already
-  /// exists in the file system with different contents.
+  /// If present, User, Group, Type and Perms apply to the newly-created file
+  /// or directory.
+  /// \return true if the file or directory was successfully added,
+  /// false if the file or directory already exists in the file system with
+  /// different contents.
   bool addFileNoOwn(const Twine &Path, time_t ModificationTime,
                     llvm::MemoryBuffer *Buffer,
                     Optional<uint32_t> User = None,
                     Optional<uint32_t> Group = None,
                     Optional<llvm::sys::fs::file_type> Type = None,
                     Optional<llvm::sys::fs::perms> Perms = None);
 
   std::string toString() const;

lib/Basic/VirtualFileSystem.cpp

bool InMemoryFileSystem::addFile(const Twine &P, time_t ModificationTime,
   // the owner, even if Perms says otherwise for the final path.
   const auto NewDirectoryPerms = ResolvedPerms | sys::fs::owner_all;
   while (true) {
     StringRef Name = *I;
     detail::InMemoryNode *Node = Dir->getChild(Name);
     ++I;
     if (!Node) {
       if (I == E) {
-        // End of the path, create a new file.
+        // End of the path, create a new file or directory.
         Status Stat(P.str(), getNextVirtualUniqueID(),
                     llvm::sys::toTimePoint(ModificationTime), ResolvedUser,
                     ResolvedGroup, Buffer->getBufferSize(), ResolvedType,
                     ResolvedPerms);
-        Dir->addChild(Name, llvm::make_unique<detail::InMemoryFile>(
-                                std::move(Stat), std::move(Buffer)));
+        std::unique_ptr<detail::InMemoryNode> child;
+        if (ResolvedType == sys::fs::file_type::directory_file) {
+          child.reset(new detail::InMemoryDirectory(std::move(Stat)));
+        } else {
+          child.reset(new detail::InMemoryFile(std::move(Stat),
+                                               std::move(Buffer)));
+        }
+        Dir->addChild(Name, std::move(child));
         return true;
       }
 
       // Create a new directory. Use the path up to here.
       Status Stat(
           StringRef(Path.str().begin(), Name.end() - Path.str().begin()),
           getNextVirtualUniqueID(), llvm::sys::toTimePoint(ModificationTime),
           ResolvedUser, ResolvedGroup, Buffer->getBufferSize(),

unittests/Basic/VirtualFileSystemTest.cpp

ASSERT_EQ(sys::fs::perms::owner_read | sys::fs::perms::owner_write |
             sys::fs::perms::owner_exe, Stat->getPermissions());
   Stat = FS.status("/a/b/c");
   ASSERT_FALSE(Stat.getError()) << Stat.getError() << "\n" << FS.toString();
   ASSERT_TRUE(Stat->isRegularFile());
   ASSERT_EQ(sys::fs::perms::owner_read | sys::fs::perms::owner_write,
             Stat->getPermissions());
 }
 
+TEST_F(InMemoryFileSystemTest, AddDirectoryThenAddChild) {
+  FS.addFile("/a", 0, MemoryBuffer::getMemBuffer(""), /*User=*/None,
+             /*Group=*/None, sys::fs::file_type::directory_file);
+  FS.addFile("/a/b", 0, MemoryBuffer::getMemBuffer("abc"), /*User=*/None,
+             /*Group=*/None, sys::fs::file_type::regular_file);
+  auto Stat = FS.status("/a");
+  ASSERT_FALSE(Stat.getError()) << Stat.getError() << "\n" << FS.toString();
+  ASSERT_TRUE(Stat->isDirectory());
+  Stat = FS.status("/a/b");
+  ASSERT_FALSE(Stat.getError()) << Stat.getError() << "\n" << FS.toString();
+  ASSERT_TRUE(Stat->isRegularFile());
+}
+
 // NOTE: in the tests below, we use '//root/' as our root directory, since it is
 // a legal *absolute* path on Windows as well as *nix.
 class VFSFromYAMLTest : public ::testing::Test {
 public:
   int NumDiagnostics;
 
   void SetUp() override { NumDiagnostics = 0; }