[YAMLVFSWriter] Fix directory handling

[jkorous]

Summary

For empty directories (except the first one) we've been adding a file with the same name as the directory to the result VFS mapping.

[JDevlieghere]

Small nit but otherwise this LGTM. Thanks for fixing this!

llvm/unittests/Support/VirtualFileSystemTest.cpp

2244

I don't have a really strong opinion about this, but I think it'd be nice to be consistent with the other tests and use a, b and c.

llvm/lib/Support/VirtualFileSystem.cpp

for (const auto &Entry : Entries.slice(1)) {
       }
       StringRef RPath = Entry.RPath;
       if (UseOverlayRelative) {
         unsigned OverlayDirLen = OverlayDir.size();
         assert(RPath.substr(0, OverlayDirLen) == OverlayDir &&
                "Overlay dir must be contained in RPath");
         RPath = RPath.slice(OverlayDirLen, RPath.size());
       }
+      if (!Entry.IsDirectory)
         writeEntry(path::filename(Entry.VPath), RPath);
     }
 
     while (!DirStack.empty()) {
       OS << "\n";
       endDirectory();
     }
     OS << "\n";
   }

llvm/unittests/Support/VirtualFileSystemTest.cpp

TEST_F(VFSFromYAMLTest, YAMLVFSWriterTest) {
   EXPECT_TRUE(FS->exists(_ab.Path));
   EXPECT_TRUE(FS->exists(_c.Path));
   EXPECT_TRUE(FS->exists(_cd.Path));
   EXPECT_TRUE(FS->exists(_e.Path));
   EXPECT_TRUE(FS->exists(_ef.Path));
   EXPECT_TRUE(FS->exists(_g.Path));
   EXPECT_TRUE(FS->exists(_h.Path));
 }
+
+TEST_F(VFSFromYAMLTest, YAMLVFSWriterTestHandleDirs) {
+  ScopedDir TestDirectory("virtual-file-system-test", /*Unique*/ true);
+  ScopedDir _a(TestDirectory + "/a");
+  ScopedDir _b(TestDirectory + "/b");
+  ScopedDir _c(TestDirectory + "/c");
+
+  vfs::YAMLVFSWriter VFSWriter;
+  VFSWriter.addDirectoryMapping(_a.Path, "//root/a");
+  VFSWriter.addDirectoryMapping(_b.Path, "//root/b");
+  VFSWriter.addDirectoryMapping(_c.Path, "//root/c");
+
+  std::string Buffer;
+  raw_string_ostream OS(Buffer);
+  VFSWriter.write(OS);
+  OS.flush();
+
+  // We didn't add a single file - only directories.
+  EXPECT_TRUE(Buffer.find("'type': 'file'") == std::string::npos);
+
+  IntrusiveRefCntPtr<ErrorDummyFileSystem> Lower(new ErrorDummyFileSystem());
+  Lower->addDirectory("//root/a");
+  Lower->addDirectory("//root/b");
+  Lower->addDirectory("//root/c");
+  // canaries
+  Lower->addRegularFile("//root/a/a");
+  Lower->addRegularFile("//root/b/b");
+  Lower->addRegularFile("//root/c/c");
+
+  IntrusiveRefCntPtr<vfs::FileSystem> FS = getFromYAMLRawString(Buffer, Lower);
+  ASSERT_TRUE(FS.get() != nullptr);
+
+  EXPECT_FALSE(FS->exists(_a.Path + "/a"));
+  EXPECT_FALSE(FS->exists(_b.Path + "/b"));
+  EXPECT_FALSE(FS->exists(_c.Path + "/c"));
+}