Index: clang-tools-extra/trunk/clangd/ClangdServer.cpp
===================================================================
--- clang-tools-extra/trunk/clangd/ClangdServer.cpp
+++ clang-tools-extra/trunk/clangd/ClangdServer.cpp
@@ -115,10 +115,15 @@
 }
 
 void ClangdServer::setRootPath(PathRef RootPath) {
-  std::string NewRootPath = llvm::sys::path::convert_to_slash(
-      RootPath, llvm::sys::path::Style::posix);
-  if (llvm::sys::fs::is_directory(NewRootPath))
-    this->RootPath = NewRootPath;
+  auto FS = FSProvider.getFileSystem();
+  auto Status = FS->status(RootPath);
+  if (!Status)
+    log("Failed to get status for RootPath " + RootPath + ": " +
+        Status.getError().message());
+  else if (Status->isDirectory())
+    this->RootPath = RootPath;
+  else
+    log("The provided RootPath " + RootPath + " is not a directory.");
 }
 
 void ClangdServer::addDocument(PathRef File, StringRef Contents,
@@ -446,7 +451,8 @@
 
 void ClangdServer::workspaceSymbols(
     StringRef Query, int Limit, Callback<std::vector<SymbolInformation>> CB) {
-  CB(clangd::getWorkspaceSymbols(Query, Limit, Index));
+  CB(clangd::getWorkspaceSymbols(Query, Limit, Index,
+                                 RootPath ? *RootPath : ""));
 }
 
 std::vector<std::pair<Path, std::size_t>>
Index: clang-tools-extra/trunk/clangd/FindSymbols.h
===================================================================
--- clang-tools-extra/trunk/clangd/FindSymbols.h
+++ clang-tools-extra/trunk/clangd/FindSymbols.h
@@ -27,9 +27,11 @@
 /// "::". For example, "std::" will list all children of the std namespace and
 /// "::" alone will list all children of the global namespace.
 /// \p Limit limits the number of results returned (0 means no limit).
+/// \p HintPath This is used when resolving URIs. If empty, URI resolution can
+/// fail if a hint path is required for the scheme of a specific URI.
 llvm::Expected<std::vector<SymbolInformation>>
 getWorkspaceSymbols(llvm::StringRef Query, int Limit,
-                    const SymbolIndex *const Index);
+                    const SymbolIndex *const Index, llvm::StringRef HintPath);
 
 } // namespace clangd
 } // namespace clang
Index: clang-tools-extra/trunk/clangd/FindSymbols.cpp
===================================================================
--- clang-tools-extra/trunk/clangd/FindSymbols.cpp
+++ clang-tools-extra/trunk/clangd/FindSymbols.cpp
@@ -95,8 +95,8 @@
 } // namespace
 
 llvm::Expected<std::vector<SymbolInformation>>
-getWorkspaceSymbols(StringRef Query, int Limit,
-                    const SymbolIndex *const Index) {
+getWorkspaceSymbols(StringRef Query, int Limit, const SymbolIndex *const Index,
+                    StringRef HintPath) {
   std::vector<SymbolInformation> Result;
   if (Query.empty() || !Index)
     return Result;
@@ -116,7 +116,7 @@
     Req.MaxCandidateCount = Limit;
   TopN<ScoredSymbolInfo, ScoredSymbolGreater> Top(Req.MaxCandidateCount);
   FuzzyMatcher Filter(Req.Query);
-  Index->fuzzyFind(Req, [&Top, &Filter](const Symbol &Sym) {
+  Index->fuzzyFind(Req, [HintPath, &Top, &Filter](const Symbol &Sym) {
     // Prefer the definition over e.g. a function declaration in a header
     auto &CD = Sym.Definition ? Sym.Definition : Sym.CanonicalDeclaration;
     auto Uri = URI::parse(CD.FileURI);
@@ -126,9 +126,7 @@
           CD.FileURI, Sym.Name));
       return;
     }
-    // FIXME: Passing no HintPath here will work for "file" and "test" schemes
-    // because they don't use it but this might not work for other custom ones.
-    auto Path = URI::resolve(*Uri);
+    auto Path = URI::resolve(*Uri, HintPath);
     if (!Path) {
       log(llvm::formatv("Workspace symbol: Could not resolve path for URI "
                         "'{0}' for symbol '{1}'.",
Index: clang-tools-extra/trunk/unittests/clangd/FindSymbolsTests.cpp
===================================================================
--- clang-tools-extra/trunk/unittests/clangd/FindSymbolsTests.cpp
+++ clang-tools-extra/trunk/unittests/clangd/FindSymbolsTests.cpp
@@ -40,13 +40,18 @@
 ClangdServer::Options optsForTests() {
   auto ServerOpts = ClangdServer::optsForTest();
   ServerOpts.BuildDynamicSymbolIndex = true;
+  ServerOpts.URISchemes = {"unittest", "file"};
   return ServerOpts;
 }
 
 class WorkspaceSymbolsTest : public ::testing::Test {
 public:
   WorkspaceSymbolsTest()
-      : Server(CDB, FSProvider, DiagConsumer, optsForTests()) {}
+      : Server(CDB, FSProvider, DiagConsumer, optsForTests()) {
+    // Make sure the test root directory is created.
+    FSProvider.Files[testPath("unused")] = "";
+    Server.setRootPath(testRoot());
+  }
 
 protected:
   MockFSProvider FSProvider;
Index: clang-tools-extra/trunk/unittests/clangd/TestFS.cpp
===================================================================
--- clang-tools-extra/trunk/unittests/clangd/TestFS.cpp
+++ clang-tools-extra/trunk/unittests/clangd/TestFS.cpp
@@ -66,7 +66,9 @@
   return Path.str();
 }
 
-/// unittest: is a scheme that refers to files relative to testRoot()
+/// unittest: is a scheme that refers to files relative to testRoot().
+/// URI body is a path relative to testRoot() e.g. unittest:///x.h for
+/// /clangd-test/x.h.
 class TestScheme : public URIScheme {
 public:
   static const char *Scheme;
@@ -75,6 +77,10 @@
   getAbsolutePath(llvm::StringRef /*Authority*/, llvm::StringRef Body,
                   llvm::StringRef HintPath) const override {
     assert(HintPath.startswith(testRoot()));
+    if (!Body.consume_front("/"))
+      return llvm::make_error<llvm::StringError>(
+          "Body of an unittest: URI must start with '/'",
+          llvm::inconvertibleErrorCode());
     llvm::SmallString<16> Path(Body.begin(), Body.end());
     llvm::sys::path::native(Path);
     return testPath(Path);
Index: clang-tools-extra/trunk/unittests/clangd/URITests.cpp
===================================================================
--- clang-tools-extra/trunk/unittests/clangd/URITests.cpp
+++ clang-tools-extra/trunk/unittests/clangd/URITests.cpp
@@ -144,7 +144,7 @@
               "/(x)/y/ z");
   EXPECT_THAT(resolveOrDie(parseOrDie("file:///c:/x/y/z")), "c:/x/y/z");
 #endif
-  EXPECT_EQ(resolveOrDie(parseOrDie("unittest:a"), testPath("x")),
+  EXPECT_EQ(resolveOrDie(parseOrDie("unittest:///a"), testPath("x")),
             testPath("a"));
 }