[clangd] Emit ranges for clangd diagnostics, and fix off-by-one positions

Summary:
 - when the diagnostic has an explicit range, we prefer that
 - if the diagnostic has a fixit, its RemoveRange is our next choice
 - otherwise we try to expand the diagnostic location into a whole token.
   (inspired by VSCode, which does this client-side when given an empty range)
 - if all else fails, we return the zero-width range as now.
   (clients react in different ways to this, highlighting a token or a char)
 - this includes the off-by-one fix from D40860, and borrows heavily from it

Reviewers: rwols, hokein

Subscribers: klimek, ilya-biryukov, cfe-commits

Differential Revision: https://reviews.llvm.org/D41118

1 files changed, 77 insertions, 16 deletions

diff --git a/clang-tools-extra/clangd/ClangdUnit.cpp b/clang-tools-extra/clangd/ClangdUnit.cpp
index 313c72edfce..c699c2f0a40 100644
--- a/clang-tools-extra/clangd/ClangdUnit.cpp
+++ b/clang-tools-extra/clangd/ClangdUnit.cpp
@@ -120,39 +120,100 @@ static int getSeverity(DiagnosticsEngine::Level L) {
   llvm_unreachable("Unknown diagnostic level!");
 }
 
-llvm::Optional<DiagWithFixIts> toClangdDiag(const StoredDiagnostic &D) {
-  auto Location = D.getLocation();
-  if (!Location.isValid() || !Location.getManager().isInMainFile(Location))
-    return llvm::None;
+// Checks whether a location is within a half-open range.
+// Note that clang also uses closed source ranges, which this can't handle!
+bool locationInRange(SourceLocation L, CharSourceRange R,
+                     const SourceManager &M) {
+  assert(R.isCharRange());
+  if (!R.isValid() || M.getFileID(R.getBegin()) != M.getFileID(R.getEnd()) ||
+      M.getFileID(R.getBegin()) != M.getFileID(L))
+    return false;
+  return L != R.getEnd() && M.isPointWithin(L, R.getBegin(), R.getEnd());
+}
 
-  Position P;
-  P.line = Location.getSpellingLineNumber() - 1;
-  P.character = Location.getSpellingColumnNumber();
-  Range R = {P, P};
-  clangd::Diagnostic Diag = {R, getSeverity(D.getLevel()), D.getMessage()};
+// Converts a half-open clang source range to an LSP range.
+// Note that clang also uses closed source ranges, which this can't handle!
+Range toRange(CharSourceRange R, const SourceManager &M) {
+  // Clang is 1-based, LSP uses 0-based indexes.
+  return {{static_cast<int>(M.getSpellingLineNumber(R.getBegin())) - 1,
+           static_cast<int>(M.getSpellingColumnNumber(R.getBegin())) - 1},
+          {static_cast<int>(M.getSpellingLineNumber(R.getEnd())) - 1,
+           static_cast<int>(M.getSpellingColumnNumber(R.getEnd())) - 1}};
+}
 
-  llvm::SmallVector<tooling::Replacement, 1> FixItsForDiagnostic;
-  for (const FixItHint &Fix : D.getFixIts()) {
-    FixItsForDiagnostic.push_back(clang::tooling::Replacement(
-        Location.getManager(), Fix.RemoveRange, Fix.CodeToInsert));
+// Clang diags have a location (shown as ^) and 0 or more ranges (~~~~).
+// LSP needs a single range.
+Range diagnosticRange(const clang::Diagnostic &D, const LangOptions &L) {
+  auto &M = D.getSourceManager();
+  auto Loc = M.getFileLoc(D.getLocation());
+  // Accept the first range that contains the location.
+  for (const auto &CR : D.getRanges()) {
+    auto R = Lexer::makeFileCharRange(CR, M, L);
+    if (locationInRange(Loc, R, M))
+      return toRange(R, M);
+  }
+  // The range may be given as a fixit hint instead.
+  for (const auto &F : D.getFixItHints()) {
+    auto R = Lexer::makeFileCharRange(F.RemoveRange, M, L);
+    if (locationInRange(Loc, R, M))
+      return toRange(R, M);
   }
-  return DiagWithFixIts{Diag, std::move(FixItsForDiagnostic)};
+  // If no suitable range is found, just use the token at the location.
+  auto R = Lexer::makeFileCharRange(CharSourceRange::getTokenRange(Loc), M, L);
+  if (!R.isValid()) // Fall back to location only, let the editor deal with it.
+    R = CharSourceRange::getCharRange(Loc);
+  return toRange(R, M);
+}
+
+TextEdit toTextEdit(const FixItHint &FixIt, const SourceManager &M,
+                    const LangOptions &L) {
+  TextEdit Result;
+  Result.range = toRange(Lexer::makeFileCharRange(FixIt.RemoveRange, M, L), M);
+  Result.newText = FixIt.CodeToInsert;
+  return Result;
+}
+
+llvm::Optional<DiagWithFixIts> toClangdDiag(const clang::Diagnostic &D,
+                                            DiagnosticsEngine::Level Level,
+                                            const LangOptions &LangOpts) {
+  if (!D.hasSourceManager() || !D.getLocation().isValid() ||
+      !D.getSourceManager().isInMainFile(D.getLocation()))
+    return llvm::None;
+
+  DiagWithFixIts Result;
+  Result.Diag.range = diagnosticRange(D, LangOpts);
+  Result.Diag.severity = getSeverity(Level);
+  SmallString<64> Message;
+  D.FormatDiagnostic(Message);
+  Result.Diag.message = Message.str();
+  for (const FixItHint &Fix : D.getFixItHints())
+    Result.FixIts.push_back(toTextEdit(Fix, D.getSourceManager(), LangOpts));
+  return std::move(Result);
 }
 
 class StoreDiagsConsumer : public DiagnosticConsumer {
 public:
   StoreDiagsConsumer(std::vector<DiagWithFixIts> &Output) : Output(Output) {}
 
+  // Track language options in case we need to expand token ranges.
+  void BeginSourceFile(const LangOptions &Opts, const Preprocessor *) override {
+    LangOpts = Opts;
+  }
+
+  void EndSourceFile() override { LangOpts = llvm::None; }
+
   void HandleDiagnostic(DiagnosticsEngine::Level DiagLevel,
                         const clang::Diagnostic &Info) override {
     DiagnosticConsumer::HandleDiagnostic(DiagLevel, Info);
 
-    if (auto convertedDiag = toClangdDiag(StoredDiagnostic(DiagLevel, Info)))
-      Output.push_back(std::move(*convertedDiag));
+    if (LangOpts)
+      if (auto D = toClangdDiag(Info, DiagLevel, *LangOpts))
+        Output.push_back(std::move(*D));
   }
 
 private:
   std::vector<DiagWithFixIts> &Output;
+  llvm::Optional<LangOptions> LangOpts;
 };
 
 template <class T> bool futureIsReady(std::shared_future<T> const &Future) {