3 files changed, 75 insertions, 16 deletions

diff --git a/clang-tools-extra/unittests/clangd/TestFS.cpp b/clang-tools-extra/unittests/clangd/TestFS.cpp
index b3081d6430b..d3112b92278 100644
--- a/clang-tools-extra/unittests/clangd/TestFS.cpp
+++ b/clang-tools-extra/unittests/clangd/TestFS.cpp
@@ -32,8 +32,10 @@ buildTestFS(llvm::StringMap<std::string> const &Files,
   return MemFS;
 }
 
-MockCompilationDatabase::MockCompilationDatabase(bool UseRelPaths)
-    : ExtraClangFlags({"-ffreestanding"}), UseRelPaths(UseRelPaths) {
+MockCompilationDatabase::MockCompilationDatabase(StringRef Directory,
+                                                 StringRef RelPathPrefix)
+    : ExtraClangFlags({"-ffreestanding"}), Directory(Directory),
+      RelPathPrefix(RelPathPrefix) {
   // -ffreestanding avoids implicit stdc-predef.h.
 }
 
@@ -42,12 +44,24 @@ MockCompilationDatabase::getCompileCommand(PathRef File) const {
   if (ExtraClangFlags.empty())
     return None;
 
-  auto CommandLine = ExtraClangFlags;
   auto FileName = sys::path::filename(File);
+
+  // Build the compile command.
+  auto CommandLine = ExtraClangFlags;
   CommandLine.insert(CommandLine.begin(), "clang");
-  CommandLine.insert(CommandLine.end(), UseRelPaths ? FileName : File);
-  return {tooling::CompileCommand(sys::path::parent_path(File), FileName,
-                                  std::move(CommandLine), "")};
+  if (RelPathPrefix.empty()) {
+    // Use the absolute path in the compile command.
+    CommandLine.push_back(File);
+  } else {
+    // Build a relative path using RelPathPrefix.
+    SmallString<32> RelativeFilePath(RelPathPrefix);
+    llvm::sys::path::append(RelativeFilePath, FileName);
+    CommandLine.push_back(RelativeFilePath.str());
+  }
+
+  return {tooling::CompileCommand(
+      Directory != StringRef() ? Directory : sys::path::parent_path(File),
+      FileName, std::move(CommandLine), "")};
 }
 
 const char *testRoot() {
diff --git a/clang-tools-extra/unittests/clangd/TestFS.h b/clang-tools-extra/unittests/clangd/TestFS.h
index 9c2a15e63d3..a0efb755d00 100644
--- a/clang-tools-extra/unittests/clangd/TestFS.h
+++ b/clang-tools-extra/unittests/clangd/TestFS.h
@@ -40,15 +40,22 @@ public:
 // A Compilation database that returns a fixed set of compile flags.
 class MockCompilationDatabase : public GlobalCompilationDatabase {
 public:
-  /// When \p UseRelPaths is true, uses relative paths in compile commands.
-  /// When \p UseRelPaths is false, uses absoulte paths.
-  MockCompilationDatabase(bool UseRelPaths = false);
+  /// If \p Directory is not empty, use that as the Directory field of the
+  /// CompileCommand.
+  ///
+  /// If \p RelPathPrefix is not empty, use that as a prefix in front of the
+  /// source file name, instead of using an absolute path.
+  MockCompilationDatabase(StringRef Directory = StringRef(),
+                          StringRef RelPathPrefix = StringRef());
 
   llvm::Optional<tooling::CompileCommand>
   getCompileCommand(PathRef File) const override;
 
   std::vector<std::string> ExtraClangFlags;
-  const bool UseRelPaths;
+
+private:
+  StringRef Directory;
+  StringRef RelPathPrefix;
 };
 
 // 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 3383dd54341..b08af32df21 100644
--- a/clang-tools-extra/unittests/clangd/XRefsTests.cpp
+++ b/clang-tools-extra/unittests/clangd/XRefsTests.cpp
@@ -312,27 +312,65 @@ TEST(GoToDefinition, All) {
 }
 
 TEST(GoToDefinition, RelPathsInCompileCommand) {
+  // The source is in "/clangd-test/src".
+  // We build in "/clangd-test/build".
+
   Annotations SourceAnnotations(R"cpp(
+#include "header_in_preamble.h"
 int [[foo]];
-int baz = f^oo;
+#include "header_not_in_preamble.h"
+int baz = f$p1^oo + bar_pre$p2^amble + bar_not_pre$p3^amble;
+)cpp");
+
+  Annotations HeaderInPreambleAnnotations(R"cpp(
+int [[bar_preamble]];
+)cpp");
+
+  Annotations HeaderNotInPreambleAnnotations(R"cpp(
+int [[bar_not_preamble]];
 )cpp");
 
+  // Make the compilation paths appear as ../src/foo.cpp in the compile
+  // commands.
+  SmallString<32> RelPathPrefix("..");
+  llvm::sys::path::append(RelPathPrefix, "src");
+  std::string BuildDir = testPath("build");
+  MockCompilationDatabase CDB(BuildDir, RelPathPrefix);
+
   IgnoreDiagnostics DiagConsumer;
-  MockCompilationDatabase CDB(/*UseRelPaths=*/true);
   MockFSProvider FS;
   ClangdServer Server(CDB, FS, DiagConsumer, ClangdServer::optsForTest());
 
-  auto FooCpp = testPath("foo.cpp");
+  // Fill the filesystem.
+  auto FooCpp = testPath("src/foo.cpp");
   FS.Files[FooCpp] = "";
+  auto HeaderInPreambleH = testPath("src/header_in_preamble.h");
+  FS.Files[HeaderInPreambleH] = HeaderInPreambleAnnotations.code();
+  auto HeaderNotInPreambleH = testPath("src/header_not_in_preamble.h");
+  FS.Files[HeaderNotInPreambleH] = HeaderNotInPreambleAnnotations.code();
 
-  Server.addDocument(FooCpp, SourceAnnotations.code());
   runAddDocument(Server, FooCpp, SourceAnnotations.code());
+
+  // Go to a definition in main source file.
   auto Locations =
-      runFindDefinitions(Server, FooCpp, SourceAnnotations.point());
+      runFindDefinitions(Server, FooCpp, SourceAnnotations.point("p1"));
   EXPECT_TRUE(bool(Locations)) << "findDefinitions returned an error";
-
   EXPECT_THAT(*Locations, ElementsAre(Location{URIForFile{FooCpp},
                                                SourceAnnotations.range()}));
+
+  // Go to a definition in header_in_preamble.h.
+  Locations = runFindDefinitions(Server, FooCpp, SourceAnnotations.point("p2"));
+  EXPECT_TRUE(bool(Locations)) << "findDefinitions returned an error";
+  EXPECT_THAT(*Locations,
+              ElementsAre(Location{URIForFile{HeaderInPreambleH},
+                                   HeaderInPreambleAnnotations.range()}));
+
+  // Go to a definition in header_not_in_preamble.h.
+  Locations = runFindDefinitions(Server, FooCpp, SourceAnnotations.point("p3"));
+  EXPECT_TRUE(bool(Locations)) << "findDefinitions returned an error";
+  EXPECT_THAT(*Locations,
+              ElementsAre(Location{URIForFile{HeaderNotInPreambleH},
+                                   HeaderNotInPreambleAnnotations.range()}));
 }
 
 TEST(Hover, All) {