[clangd] Handle clang-tidy suppression comments for diagnostics inside macro expansions

Summary:
Not handling this was a side-effect of being overly cautious when trying
to avoid reading files for which clangd doesn't have the source mapped.

Fixes https://github.com/clangd/clangd/issues/266

Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet,
usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75286

clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp

@@ -296,57 +296,54 @@ static bool IsNOLINTFound(StringRef NolintDirectiveText, StringRef Line,
   return true;
 }
 
+llvm::Optional<StringRef> getBuffer(const SourceManager &SM, FileID File,
+                                    bool AllowIO) {
+  // This is similar to the implementation of SourceManager::getBufferData(),
+  // but uses ContentCache::getRawBuffer() rather than getBuffer() if
+  // AllowIO=false, to avoid triggering file I/O if the file contents aren't
+  // already mapped.
+  bool CharDataInvalid = false;
+  const SrcMgr::SLocEntry &Entry = SM.getSLocEntry(File, &CharDataInvalid);
+  if (CharDataInvalid || !Entry.isFile())
+    return llvm::None;
+  const SrcMgr::ContentCache *Cache = Entry.getFile().getContentCache();
+  const llvm::MemoryBuffer *Buffer =
+      AllowIO ? Cache->getBuffer(SM.getDiagnostics(), SM.getFileManager(),
+                                 SourceLocation(), &CharDataInvalid)
+              : Cache->getRawBuffer();
+  if (!Buffer || CharDataInvalid)
+    return llvm::None;
+  return Buffer->getBuffer();
+}
+
 static bool LineIsMarkedWithNOLINT(const SourceManager &SM, SourceLocation Loc,
                                    unsigned DiagID,
-                                   const ClangTidyContext &Context) {
-  bool Invalid;
-  const char *CharacterData = SM.getCharacterData(Loc, &Invalid);
-  if (Invalid)
+                                   const ClangTidyContext &Context,
+                                   bool AllowIO) {
+  FileID File;
+  unsigned Offset;
+  std::tie(File, Offset) = SM.getDecomposedSpellingLoc(Loc);
+  llvm::Optional<StringRef> Buffer = getBuffer(SM, File, AllowIO);
+  if (!Buffer)
     return false;
 
   // Check if there's a NOLINT on this line.
-  const char *P = CharacterData;
-  while (*P != '\0' && *P != '\r' && *P != '\n')
-    ++P;
-  StringRef RestOfLine(CharacterData, P - CharacterData + 1);
+  StringRef RestOfLine = Buffer->substr(Offset).split('\n').first;
   if (IsNOLINTFound("NOLINT", RestOfLine, DiagID, Context))
     return true;
 
   // Check if there's a NOLINTNEXTLINE on the previous line.
-  const char *BufBegin =
-      SM.getCharacterData(SM.getLocForStartOfFile(SM.getFileID(Loc)), &Invalid);
-  if (Invalid || P == BufBegin)
-    return false;
-
-  // Scan backwards over the current line.
-  P = CharacterData;
-  while (P != BufBegin && *P != '\n')
-    --P;
-
-  // If we reached the begin of the file there is no line before it.
-  if (P == BufBegin)
-    return false;
-
-  // Skip over the newline.
-  --P;
-  const char *LineEnd = P;
-
-  // Now we're on the previous line. Skip to the beginning of it.
-  while (P != BufBegin && *P != '\n')
-    --P;
-
-  RestOfLine = StringRef(P, LineEnd - P + 1);
-  if (IsNOLINTFound("NOLINTNEXTLINE", RestOfLine, DiagID, Context))
-    return true;
-
-  return false;
+  StringRef PrevLine =
+      Buffer->substr(0, Offset).rsplit('\n').first.rsplit('\n').second;
+  return IsNOLINTFound("NOLINTNEXTLINE", PrevLine, DiagID, Context);
 }
 
 static bool LineIsMarkedWithNOLINTinMacro(const SourceManager &SM,
                                           SourceLocation Loc, unsigned DiagID,
-                                          const ClangTidyContext &Context) {
+                                          const ClangTidyContext &Context,
+                                          bool AllowIO) {
   while (true) {
-    if (LineIsMarkedWithNOLINT(SM, Loc, DiagID, Context))
+    if (LineIsMarkedWithNOLINT(SM, Loc, DiagID, Context, AllowIO))
       return true;
     if (!Loc.isMacroID())
       return false;
@@ -360,14 +357,13 @@ namespace tidy {
 
 bool shouldSuppressDiagnostic(DiagnosticsEngine::Level DiagLevel,
                               const Diagnostic &Info, ClangTidyContext &Context,
-                              bool CheckMacroExpansion) {
+                              bool AllowIO) {
   return Info.getLocation().isValid() &&
          DiagLevel != DiagnosticsEngine::Error &&
          DiagLevel != DiagnosticsEngine::Fatal &&
-         (CheckMacroExpansion ? LineIsMarkedWithNOLINTinMacro
-                              : LineIsMarkedWithNOLINT)(Info.getSourceManager(),
-                                                        Info.getLocation(),
-                                                        Info.getID(), Context);
+         LineIsMarkedWithNOLINTinMacro(Info.getSourceManager(),
+                                       Info.getLocation(), Info.getID(),
+                                       Context, AllowIO);
 }
 
 } // namespace tidy

clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.h

@@ -216,15 +216,12 @@ private:
 /// This does not handle suppression of notes following a suppressed diagnostic;
 /// that is left to the caller is it requires maintaining state in between calls
 /// to this function.
-/// The `CheckMacroExpansion` parameter determines whether the function should
-/// handle the case where the diagnostic is inside a macro expansion. A degree
-/// of control over this is needed because handling this case can require
-/// examining source files other than the one in which the diagnostic is
-/// located, and in some use cases we cannot rely on such other files being
-/// mapped in the SourceMapper.
+/// If `AllowIO` is false, the function does not attempt to read source files
+/// from disk which are not already mapped into memory; such files are treated
+/// as not containing a suppression comment.
 bool shouldSuppressDiagnostic(DiagnosticsEngine::Level DiagLevel,
                               const Diagnostic &Info, ClangTidyContext &Context,
-                              bool CheckMacroExpansion = true);
+                              bool AllowIO = true);
 
 /// A diagnostic consumer that turns each \c Diagnostic into a
 /// \c SourceManager-independent \c ClangTidyError.

clang-tools-extra/clangd/ParsedAST.cpp

@@ -310,14 +310,13 @@ ParsedAST::build(llvm::StringRef Version,
           // Check for suppression comment. Skip the check for diagnostics not
           // in the main file, because we don't want that function to query the
           // source buffer for preamble files. For the same reason, we ask
-          // shouldSuppressDiagnostic not to follow macro expansions, since
-          // those might take us into a preamble file as well.
+          // shouldSuppressDiagnostic to avoid I/O.
           bool IsInsideMainFile =
               Info.hasSourceManager() &&
               isInsideMainFile(Info.getLocation(), Info.getSourceManager());
-          if (IsInsideMainFile && tidy::shouldSuppressDiagnostic(
-                                      DiagLevel, Info, *CTContext,
-                                      /* CheckMacroExpansion = */ false)) {
+          if (IsInsideMainFile &&
+              tidy::shouldSuppressDiagnostic(DiagLevel, Info, *CTContext,
+                                             /*AllowIO=*/false)) {
             return DiagnosticsEngine::Ignored;
           }
         }

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

@@ -272,7 +272,11 @@ TEST(DiagnosticTest, ClangTidySuppressionComment) {
       double d = 8 / i;  // NOLINT
       // NOLINTNEXTLINE
       double e = 8 / i;
-      double f = [[8]] / i;
+      #define BAD 8 / i
+      double f = BAD;  // NOLINT
+      double g = [[8]] / i;
+      #define BAD2 BAD
+      double h = BAD2;  // NOLINT
     }
   )cpp");
   TestTU TU = TestTU::withCode(Main.code());