[clangd] Use the index-based API to do the header-source switch.

[hokein]

Summary

If the file heuristic fails, we try to use the index&AST to do the
header/source inference.

[kadircet]

thanks, mostly LG

clang-tools-extra/clangd/ClangdServer.cpp

453

could you add some comments explaining, why we first use file-only version(speed) and why try with an ast&index afterwards(making use of declarations)

clang-tools-extra/clangd/ClangdServer.h

194–195

i don't think it is a helper function anymore

clang-tools-extra/clangd/unittests/HeaderSourceSwitchTests.cpp

250

could we rather provide testPath("src/include") to make sure this also works on windows?

[hokein]

address comments.

[kadircet]

some nits, thanks!

clang-tools-extra/clangd/ClangdServer.cpp

456

AST, it works -> AST, but it only works

456

indent one more column

458

s/works for/supports

[hokein]

address comments.

clang-tools-extra/clangd/ClangdLSPServer.cpp

Server->locateSymbolAt(
         }
         Reply(std::move(Decls));
       });
 }
 
 void ClangdLSPServer::onSwitchSourceHeader(
     const TextDocumentIdentifier &Params,
     Callback<llvm::Optional<URIForFile>> Reply) {
-  if (auto Result = Server->switchSourceHeader(Params.uri.file()))
-    Reply(URIForFile::canonicalize(*Result, Params.uri.file()));
-  else
-    Reply(llvm::None);
+  Server->switchSourceHeader(
+      Params.uri.file(),
+      [Reply = std::move(Reply),
+       Params](llvm::Expected<llvm::Optional<clangd::Path>> Path) mutable {
+        if (!Path)
+          return Reply(Path.takeError());
+        if (*Path)
+          Reply(URIForFile::canonicalize(**Path, Params.uri.file()));
+        return Reply(llvm::None);
+      });
 }
 
 void ClangdLSPServer::onDocumentHighlight(
     const TextDocumentPositionParams &Params,
     Callback<std::vector<DocumentHighlight>> Reply) {
   Server->findDocumentHighlights(Params.textDocument.uri.file(),
                                  Params.position, std::move(Reply));
 }

clang-tools-extra/clangd/ClangdServer.h

public:
 
   /// Provide signature help for \p File at \p Pos.  This method should only be
   /// called for tracked files.
   void signatureHelp(PathRef File, Position Pos, Callback<SignatureHelp> CB);
 
   /// Find declaration/definition locations of symbol at a specified position.
   void locateSymbolAt(PathRef File, Position Pos,
                       Callback<std::vector<LocatedSymbol>> CB);
 
-  /// Helper function that returns a path to the corresponding source file when
-  /// given a header file and vice versa.
-  llvm::Optional<Path> switchSourceHeader(PathRef Path);
+  /// Switch to a corresponding source file when given a header file, and vice
+  /// versa.
+  void switchSourceHeader(PathRef Path,
+                          Callback<llvm::Optional<clangd::Path>> CB);
 
   /// Get document highlights for a given position.
   void findDocumentHighlights(PathRef File, Position Pos,
                               Callback<std::vector<DocumentHighlight>> CB);
 
   /// Get code hover for a given position.
   void findHover(PathRef File, Position Pos,
                  Callback<llvm::Optional<HoverInfo>> CB);

clang-tools-extra/clangd/ClangdServer.cpp

auto Action = [Pos, CB = std::move(CB),
     if (!InpAST)
       return CB(InpAST.takeError());
     CB(clangd::locateSymbolAt(InpAST->AST, Pos, Index));
   };
 
   WorkScheduler.runWithAST("Definitions", File, std::move(Action));
 }
 
-llvm::Optional<Path> ClangdServer::switchSourceHeader(PathRef Path) {
-  return getCorrespondingHeaderOrSource(Path, FSProvider.getFileSystem());
+void ClangdServer::switchSourceHeader(
+    PathRef Path, Callback<llvm::Optional<clangd::Path>> CB) {
+  // We want to return the result as fast as possible, stragety is:
+  //  1) use the file-only heuristic, it requires some IO but it is much
+  //     faster than building AST, but it only works when .h/.cc files are in
+  //     the same directory.
+  //  2) if 1) fails, we use the AST&Index approach, it is slower but supports
+  //     different code layout.
+  if (auto CorrespondingFile =
+          getCorrespondingHeaderOrSource(Path, FSProvider.getFileSystem()))
+    return CB(std::move(CorrespondingFile));
+  auto Action = [Path, CB = std::move(CB),
+                 this](llvm::Expected<InputsAndAST> InpAST) mutable {
+    if (!InpAST)
+      return CB(InpAST.takeError());
+    CB(getCorrespondingHeaderOrSource(Path, InpAST->AST, Index));
+  };
+  WorkScheduler.runWithAST("SwitchHeaderSource", Path, std::move(Action));
 }
 
 llvm::Expected<tooling::Replacements>
 ClangdServer::formatCode(llvm::StringRef Code, PathRef File,
                          llvm::ArrayRef<tooling::Range> Ranges) {
   // Call clang-format.
   format::FormatStyle Style =
       getFormatStyleForFile(File, Code, FSProvider.getFileSystem().get());

clang-tools-extra/clangd/unittests/HeaderSourceSwitchTests.cpp

 //===--- HeaderSourceSwitchTests.cpp - ---------------------------*- C++-*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "HeaderSourceSwitch.h"
 
+#include "SyncAPI.h"
 #include "TestFS.h"
 #include "TestTU.h"
 #include "index/MemIndex.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 
 namespace clang {
 namespace clangd {
for (const auto &Case : TestCases) {
     TU.Filename = "Test.cpp";
     auto AST = TU.build();
     EXPECT_EQ(Case.ExpectedResult,
               getCorrespondingHeaderOrSource(testPath(TU.Filename), AST,
                                              Index.get()));
   }
 }
 
+TEST(HeaderSourceSwitchTest, ClangdServerIntegration) {
+  class IgnoreDiagnostics : public DiagnosticsConsumer {
+    void onDiagnosticsReady(PathRef File,
+                            std::vector<Diag> Diagnostics) override {}
+  } DiagConsumer;
+  MockCompilationDatabase CDB;
+  CDB.ExtraClangFlags = {"-I" +
+                         testPath("src/include")}; // add search directory.
+  MockFSProvider FS;
+  // File heuristic fails here, we rely on the index to find the .h file.
+  std::string CppPath = testPath("src/lib/test.cpp");
+  std::string HeaderPath = testPath("src/include/test.h");
+  FS.Files[HeaderPath] = "void foo();";
+  const std::string FileContent = R"cpp(
+    #include "test.h"
+    void foo() {};
+  )cpp";
+  FS.Files[CppPath] = FileContent;
+  auto Options = ClangdServer::optsForTest();
+  Options.BuildDynamicSymbolIndex = true;
+  ClangdServer Server(CDB, FS, DiagConsumer, Options);
+  runAddDocument(Server, CppPath, FileContent);
+  EXPECT_EQ(HeaderPath,
+            *llvm::cantFail(runSwitchHeaderSource(Server, CppPath)));
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang

clang-tools-extra/clangd/unittests/SyncAPI.h

 
 SymbolSlab runFuzzyFind(const SymbolIndex &Index, StringRef Query);
 SymbolSlab runFuzzyFind(const SymbolIndex &Index, const FuzzyFindRequest &Req);
 RefSlab getRefs(const SymbolIndex &Index, SymbolID ID);
 
 llvm::Expected<std::vector<Range>>
 runSemanticRanges(ClangdServer &Server, PathRef File, Position Pos);
 
+llvm::Expected<llvm::Optional<clangd::Path>>
+runSwitchHeaderSource(ClangdServer &Server, PathRef File);
+
 } // namespace clangd
 } // namespace clang
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_UNITTESTS_CLANGD_SYNCAPI_H

clang-tools-extra/clangd/unittests/SyncAPI.cpp

 
 llvm::Expected<std::vector<Range>>
 runSemanticRanges(ClangdServer &Server, PathRef File, Position Pos) {
   llvm::Optional<llvm::Expected<std::vector<Range>>> Result;
   Server.semanticRanges(File, Pos, capture(Result));
   return std::move(*Result);
 }
 
+llvm::Expected<llvm::Optional<clangd::Path>>
+runSwitchHeaderSource(ClangdServer &Server, PathRef File) {
+  llvm::Optional<llvm::Expected<llvm::Optional<clangd::Path>>> Result;
+  Server.switchSourceHeader(File, capture(Result));
+  return std::move(*Result);
+}
+
 } // namespace clangd
 } // namespace clang