[clangd] Drop documentation in static index if symbols are not indexed for completion.

Summary:
This is a further optimization of r350803, we drop docs in static index for
symbols not being indexed for completion, while keeping the docs in dynamic
index (we rely on dynamic index to get docs for class members).

Reviewers: ilya-biryukov

Reviewed By: ilya-biryukov

Subscribers: ioeric, MaskRay, jkorous, arphaman, kadircet, cfe-commits

Differential Revision: https://reviews.llvm.org/D56539

llvm-svn: 354792

clang-tools-extra/clangd/index/FileIndex.cpp

@@ -45,9 +45,13 @@ indexSymbols(ASTContext &AST, std::shared_ptr<Preprocessor> PP,
   if (IsIndexMainAST) {
     // We only collect refs when indexing main AST.
     CollectorOpts.RefFilter = RefKind::All;
+    // Comments for main file can always be obtained from sema, do not store
+    // them in the index.
+    CollectorOpts.StoreAllDocumentation = false;
   } else {
     IndexOpts.IndexMacrosInPreprocessor = true;
     CollectorOpts.CollectMacro = true;
+    CollectorOpts.StoreAllDocumentation = true;
   }
 
   SymbolCollector Collector(std::move(CollectorOpts));

clang-tools-extra/clangd/index/IndexAction.cpp

@@ -175,6 +175,7 @@ std::unique_ptr<FrontendAction> createStaticIndexingAction(
   Opts.CollectIncludePath = true;
   Opts.CountReferences = true;
   Opts.Origin = SymbolOrigin::Static;
+  Opts.StoreAllDocumentation = false;
   if (RefsCallback != nullptr) {
     Opts.RefFilter = RefKind::All;
     Opts.RefsInHeaders = true;

clang-tools-extra/clangd/index/SymbolCollector.cpp

@@ -566,18 +566,13 @@ const Symbol *SymbolCollector::addDeclaration(const NamedDecl &ND,
   std::string Documentation =
       formatDocumentation(*CCS, getDocComment(Ctx, SymbolCompletion,
                                               /*CommentsFromHeaders=*/true));
-  // For symbols not indexed for completion (class members), we also store their
-  // docs in the index, because Sema doesn't load the docs from the preamble, we
-  // rely on the index to get the docs.
-  // FIXME: this can be optimized by only storing the docs in dynamic index --
-  // dynamic index should index these symbols when Sema completes a member
-  // completion.
-  S.Documentation = Documentation;
   if (!(S.Flags & Symbol::IndexedForCodeCompletion)) {
+    if (Opts.StoreAllDocumentation)
+      S.Documentation = Documentation;
     Symbols.insert(S);
     return Symbols.find(S.ID);
   }
-
+  S.Documentation = Documentation;
   std::string Signature;
   std::string SnippetSuffix;
   getSignature(*CCS, &Signature, &SnippetSuffix);

clang-tools-extra/clangd/index/SymbolCollector.h

@@ -75,6 +75,10 @@ public:
     /// Collect symbols local to main-files, such as static functions
     /// and symbols inside an anonymous namespace.
     bool CollectMainFileSymbols = true;
+    /// If set to true, SymbolCollector will collect doc for all symbols.
+    /// Note that documents of symbols being indexed for completion will always
+    /// be collected regardless of this option.
+    bool StoreAllDocumentation = false;
     /// If this is set, only collect symbols/references from a file if
     /// `FileFilter(SM, FID)` is true. If not set, all files are indexed.
     std::function<bool(const SourceManager &, FileID)> FileFilter = nullptr;

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

@@ -212,6 +212,12 @@ public:
         return WrapperFrontendAction::CreateASTConsumer(CI, InFile);
       }
 
+      bool BeginInvocation(CompilerInstance &CI) override {
+        // Make the compiler parse all comments.
+        CI.getLangOpts().CommentOpts.ParseAllComments = true;
+        return WrapperFrontendAction::BeginInvocation(CI);
+      }
+
     private:
       index::IndexingOptions IndexOpts;
       CommentHandler *PragmaHandler;
@@ -710,6 +716,31 @@ TEST_F(SymbolCollectorTest, SymbolsInMainFile) {
                                    QName("main_f")));
 }
 
+TEST_F(SymbolCollectorTest, Documentation) {
+  const std::string Header = R"(
+    // Doc Foo
+    class Foo {
+      // Doc f
+      int f();
+    };
+  )";
+  CollectorOpts.StoreAllDocumentation = false;
+  runSymbolCollector(Header, /* Main */ "");
+  EXPECT_THAT(Symbols,
+              UnorderedElementsAre(
+                  AllOf(QName("Foo"), Doc("Doc Foo"), ForCodeCompletion(true)),
+                  AllOf(QName("Foo::f"), Doc(""), ReturnType(""),
+                        ForCodeCompletion(false))));
+
+  CollectorOpts.StoreAllDocumentation = true;
+  runSymbolCollector(Header, /* Main */ "");
+  EXPECT_THAT(Symbols,
+              UnorderedElementsAre(
+                  AllOf(QName("Foo"), Doc("Doc Foo"), ForCodeCompletion(true)),
+                  AllOf(QName("Foo::f"), Doc("Doc f"), ReturnType(""),
+                        ForCodeCompletion(false))));
+}
+
 TEST_F(SymbolCollectorTest, ClassMembers) {
   const std::string Header = R"(
     class Foo {