[clang][Index] Add a knob to index function parameters in declarations

[kadircet]

Summary

Parameters in declarations are useful for clangd, so that we can
provide symbol information for them as well. It also helps clangd to be
consistent whether a function's definition is accessible or not.

[kadircet]

• Also delete comment

[hokein]

The change looks reasonable, I'd wait for a few days before commit in case anyone has concerns.

include/clang/Index/IndexingAction.h

47

nit: Only meaningful when IndexFunctionLocals is true?

include/clang/Index/IndexingAction.h

struct IndexingOptions {
   SystemSymbolFilterKind SystemSymbolFilter
     = SystemSymbolFilterKind::DeclarationsOnly;
   bool IndexFunctionLocals = false;
   bool IndexImplicitInstantiation = false;
   // Whether to index macro definitions in the Preprocesor when preprocessor
   // callback is not available (e.g. after parsing has finished). Note that
   // macro references are not available in Proprocessor.
   bool IndexMacrosInPreprocessor = false;
+  // Has no effect if IndexFunctionLocals are false.
+  bool IndexParametersInDeclarations = false;
 };
 
 /// Creates a frontend action that indexes all symbols (macros and AST decls).
 /// \param WrappedAction another frontend action to wrap over or null.
 std::unique_ptr<FrontendAction>
 createIndexingAction(std::shared_ptr<IndexDataConsumer> DataConsumer,
                      IndexingOptions Opts,
                      std::unique_ptr<FrontendAction> WrappedAction);

lib/Index/IndexDecl.cpp

IndexCtx.indexTypeSourceInfo(D->getTypeSourceInfo(), Parent,
                                  /*isBase=*/false, isIBType);
     IndexCtx.indexNestedNameSpecifierLoc(D->getQualifierLoc(), Parent);
     if (IndexCtx.shouldIndexFunctionLocalSymbols()) {
       // Only index parameters in definitions, parameters in declarations are
       // not useful.
       if (const ParmVarDecl *Parm = dyn_cast<ParmVarDecl>(D)) {
         auto *DC = Parm->getDeclContext();
         if (auto *FD = dyn_cast<FunctionDecl>(DC)) {
-          if (FD->isThisDeclarationADefinition())
+          if (IndexCtx.shouldIndexParametersInDeclarations() ||
+              FD->isThisDeclarationADefinition())
             IndexCtx.handleDecl(Parm);
         } else if (auto *MD = dyn_cast<ObjCMethodDecl>(DC)) {
           if (MD->isThisDeclarationADefinition())
             IndexCtx.handleDecl(Parm);
         } else {
           IndexCtx.handleDecl(Parm);
         }
       } else if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
-        if (FD->isThisDeclarationADefinition()) {
+        if (IndexCtx.shouldIndexParametersInDeclarations() ||
+            FD->isThisDeclarationADefinition()) {
           for (auto PI : FD->parameters()) {
             IndexCtx.handleDecl(PI);
           }
         }
       }
     } else {
       // Index the default parameter value for function definitions.
       if (const auto *FD = dyn_cast<FunctionDecl>(D)) {

lib/Index/IndexingContext.h

public:
   bool shouldSuppressRefs() const {
     return false;
   }
 
   bool shouldIndexFunctionLocalSymbols() const;
 
   bool shouldIndexImplicitInstantiation() const;
 
+  bool shouldIndexParametersInDeclarations() const;
+
   static bool isTemplateImplicitInstantiation(const Decl *D);
 
   bool handleDecl(const Decl *D, SymbolRoleSet Roles = SymbolRoleSet(),
                   ArrayRef<SymbolRelation> Relations = None);
 
   bool handleDecl(const Decl *D, SourceLocation Loc,
                   SymbolRoleSet Roles = SymbolRoleSet(),
                   ArrayRef<SymbolRelation> Relations = None,

lib/Index/IndexingContext.cpp

 bool IndexingContext::shouldIndexFunctionLocalSymbols() const {
   return IndexOpts.IndexFunctionLocals;
 }
 
 bool IndexingContext::shouldIndexImplicitInstantiation() const {
   return IndexOpts.IndexImplicitInstantiation;
 }
 
+bool IndexingContext::shouldIndexParametersInDeclarations() const {
+  return IndexOpts.IndexParametersInDeclarations;
+}
+
 bool IndexingContext::handleDecl(const Decl *D,
                                  SymbolRoleSet Roles,
                                  ArrayRef<SymbolRelation> Relations) {
   return handleDecl(D, D->getLocation(), Roles, Relations);
 }
 
 bool IndexingContext::handleDecl(const Decl *D, SourceLocation Loc,
                                  SymbolRoleSet Roles,

unittests/Index/IndexTests.cpp

TEST(IndexTest, IndexPreprocessorMacros) {
   EXPECT_THAT(Index->Symbols, Contains(QName("INDEX_MAC")));
 
   Opts.IndexMacrosInPreprocessor = false;
   Index->Symbols.clear();
   tooling::runToolOnCode(new IndexAction(Index, Opts), Code);
   EXPECT_THAT(Index->Symbols, UnorderedElementsAre());
 }
 
+TEST(IndexTest, IndexParametersInDecls) {
+  std::string Code = "void foo(int bar);";
+  auto Index = std::make_shared<Indexer>();
+  IndexingOptions Opts;
+  Opts.IndexFunctionLocals = true;
+  Opts.IndexParametersInDeclarations = true;
+  tooling::runToolOnCode(new IndexAction(Index, Opts), Code);
+  EXPECT_THAT(Index->Symbols, Contains(QName("bar")));
+
+  Opts.IndexParametersInDeclarations = false;
+  Index->Symbols.clear();
+  tooling::runToolOnCode(new IndexAction(Index, Opts), Code);
+  EXPECT_THAT(Index->Symbols, Not(Contains(QName("bar"))));
+}
+
 } // namespace
 } // namespace index
 } // namespace clang