4 files changed, 51 insertions, 8 deletions

diff --git a/clang-tools-extra/clangd/XRefs.cpp b/clang-tools-extra/clangd/XRefs.cpp
index e7ded2ee1e8..6f43353dce6 100644
--- a/clang-tools-extra/clangd/XRefs.cpp
+++ b/clang-tools-extra/clangd/XRefs.cpp
@@ -11,6 +11,7 @@
 #include "URI.h"
 #include "clang/Index/IndexDataConsumer.h"
 #include "clang/Index/IndexingAction.h"
+#include "llvm/Support/Path.h"
 namespace clang {
 namespace clangd {
 using namespace llvm;
@@ -138,10 +139,17 @@ getDeclarationLocation(ParsedAST &AST, const SourceRange &ValSourceRange) {
   Range R = {Begin, End};
   Location L;
 
-  StringRef FilePath = F->tryGetRealPathName();
+  SmallString<64> FilePath = F->tryGetRealPathName();
   if (FilePath.empty())
     FilePath = F->getName();
-  L.uri.file = FilePath;
+  if (!llvm::sys::path::is_absolute(FilePath)) {
+    if (!SourceMgr.getFileManager().makeAbsolutePath(FilePath)) {
+      log("Could not turn relative path to absolute: " + FilePath);
+      return llvm::None;
+    }
+  }
+
+  L.uri.file = FilePath.str();
   L.range = R;
   return L;
 }
diff --git a/clang-tools-extra/unittests/clangd/TestFS.cpp b/clang-tools-extra/unittests/clangd/TestFS.cpp
index 55506e6c4e0..38cef894074 100644
--- a/clang-tools-extra/unittests/clangd/TestFS.cpp
+++ b/clang-tools-extra/unittests/clangd/TestFS.cpp
@@ -33,8 +33,10 @@ MockFSProvider::getTaggedFileSystem(PathRef File) {
   return make_tagged(FS, Tag);
 }
 
-MockCompilationDatabase::MockCompilationDatabase()
-    : ExtraClangFlags({"-ffreestanding"}) {} // Avoid implicit stdc-predef.h.
+MockCompilationDatabase::MockCompilationDatabase(bool UseRelPaths)
+    : ExtraClangFlags({"-ffreestanding"}), UseRelPaths(UseRelPaths) {
+  // -ffreestanding avoids implicit stdc-predef.h.
+}
 
 llvm::Optional<tooling::CompileCommand>
 MockCompilationDatabase::getCompileCommand(PathRef File) const {
@@ -42,10 +44,10 @@ MockCompilationDatabase::getCompileCommand(PathRef File) const {
     return llvm::None;
 
   auto CommandLine = ExtraClangFlags;
+  auto FileName = llvm::sys::path::filename(File);
   CommandLine.insert(CommandLine.begin(), "clang");
-  CommandLine.insert(CommandLine.end(), File.str());
-  return {tooling::CompileCommand(llvm::sys::path::parent_path(File),
-                                  llvm::sys::path::filename(File),
+  CommandLine.insert(CommandLine.end(), UseRelPaths ? FileName : File);
+  return {tooling::CompileCommand(llvm::sys::path::parent_path(File), FileName,
                                   std::move(CommandLine), "")};
 }
 
diff --git a/clang-tools-extra/unittests/clangd/TestFS.h b/clang-tools-extra/unittests/clangd/TestFS.h
index 6ff1c662201..5edde1fff9e 100644
--- a/clang-tools-extra/unittests/clangd/TestFS.h
+++ b/clang-tools-extra/unittests/clangd/TestFS.h
@@ -37,12 +37,15 @@ public:
 // A Compilation database that returns a fixed set of compile flags.
 class MockCompilationDatabase : public GlobalCompilationDatabase {
 public:
-  MockCompilationDatabase();
+  /// When \p UseRelPaths is true, uses relative paths in compile commands.
+  /// When \p UseRelPaths is false, uses absoulte paths.
+  MockCompilationDatabase(bool UseRelPaths = false);
 
   llvm::Optional<tooling::CompileCommand>
   getCompileCommand(PathRef File) const override;
 
   std::vector<std::string> ExtraClangFlags;
+  const bool UseRelPaths;
 };
 
 // Returns an absolute (fake) test directory for this OS.
diff --git a/clang-tools-extra/unittests/clangd/XRefsTests.cpp b/clang-tools-extra/unittests/clangd/XRefsTests.cpp
index 59e30725ba0..50d24c50113 100644
--- a/clang-tools-extra/unittests/clangd/XRefsTests.cpp
+++ b/clang-tools-extra/unittests/clangd/XRefsTests.cpp
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 #include "Annotations.h"
 #include "ClangdUnit.h"
+#include "Compiler.h"
 #include "Matchers.h"
 #include "TestFS.h"
 #include "XRefs.h"
@@ -37,6 +38,11 @@ using testing::Field;
 using testing::Matcher;
 using testing::UnorderedElementsAreArray;
 
+class IgnoreDiagnostics : public DiagnosticsConsumer {
+  void onDiagnosticsReady(
+      PathRef File, Tagged<std::vector<DiagWithFixIts>> Diagnostics) override {}
+};
+
 // FIXME: this is duplicated with FileIndexTests. Share it.
 ParsedAST build(StringRef Code) {
   auto TestFile = getVirtualTestFilePath("Foo.cpp");
@@ -227,6 +233,30 @@ TEST(GoToDefinition, All) {
   }
 }
 
+TEST(GoToDefinition, RelPathsInCompileCommand) {
+  Annotations SourceAnnotations(R"cpp(
+[[int foo]];
+int baz = f^oo;
+)cpp");
+
+  IgnoreDiagnostics DiagConsumer;
+  MockCompilationDatabase CDB(/*UseRelPaths=*/true);
+  MockFSProvider FS;
+  ClangdServer Server(CDB, DiagConsumer, FS, /*AsyncThreadsCount=*/0,
+                      /*StorePreambleInMemory=*/true);
+
+  auto FooCpp = getVirtualTestFilePath("foo.cpp");
+  FS.Files[FooCpp] = "";
+
+  Server.addDocument(FooCpp, SourceAnnotations.code());
+  auto Locations = Server.findDefinitions(FooCpp, SourceAnnotations.point());
+  EXPECT_TRUE(bool(Locations)) << "findDefinitions returned an error";
+
+  EXPECT_THAT(Locations->Value,
+              ElementsAre(Location{URIForFile{FooCpp.str()},
+                                   SourceAnnotations.range()}));
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang