[clangd] Don't store completion info if the symbol is not used for code completion.

Summary:
This would save us some memory and disk space:
  - Dex usage (261 MB vs 266 MB)
  - Disk (75 MB vs 76 MB)

It would save more when we index the main file symbol D55185.

Reviewers: ilya-biryukov

Reviewed By: ilya-biryukov

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

Differential Revision: https://reviews.llvm.org/D56314

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@350803 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 38 insertions, 14 deletions

diff --git a/clangd/index/Index.h b/clangd/index/Index.h
index a5552d4f..1ab9ecd6 100644
--- a/clangd/index/Index.h
+++ b/clangd/index/Index.h
@@ -185,19 +185,23 @@ struct Symbol {
   SymbolOrigin Origin = SymbolOrigin::Unknown;
   /// A brief description of the symbol that can be appended in the completion
   /// candidate list. For example, "(X x, Y y) const" is a function signature.
+  /// Only set when the symbol is indexed for completion.
   llvm::StringRef Signature;
   /// What to insert when completing this symbol, after the symbol name.
   /// This is in LSP snippet syntax (e.g. "({$0})" for a no-args function).
   /// (When snippets are disabled, the symbol name alone is used).
+  /// Only set when the symbol is indexed for completion.
   llvm::StringRef CompletionSnippetSuffix;
   /// Documentation including comment for the symbol declaration.
   llvm::StringRef Documentation;
   /// Type when this symbol is used in an expression. (Short display form).
   /// e.g. return type of a function, or type of a variable.
+  /// Only set when the symbol is indexed for completion.
   llvm::StringRef ReturnType;
 
   /// Raw representation of the OpaqueType of the symbol, used for scoring
   /// purposes.
+  /// Only set when the symbol is indexed for completion.
   llvm::StringRef Type;
 
   struct IncludeHeaderWithReferences {
@@ -223,12 +227,15 @@ struct Symbol {
   ///   - If we haven't seen a definition, this covers all declarations.
   ///   - If we have seen a definition, this covers declarations visible from
   ///   any definition.
+  /// Only set when the symbol is indexed for completion.
   llvm::SmallVector<IncludeHeaderWithReferences, 1> IncludeHeaders;
 
   enum SymbolFlag : uint8_t {
     None = 0,
     /// Whether or not this symbol is meant to be used for the code completion.
     /// See also isIndexedForCodeCompletion().
+    /// Note that we don't store completion information (signature, snippet,
+    /// type, inclues) if the symbol is not indexed for code completion.
     IndexedForCodeCompletion = 1 << 0,
     /// Indicates if the symbol is deprecated.
     Deprecated = 1 << 1,
diff --git a/clangd/index/SymbolCollector.cpp b/clangd/index/SymbolCollector.cpp
index cdc6aa5c..23b1776a 100644
--- a/clangd/index/SymbolCollector.cpp
+++ b/clangd/index/SymbolCollector.cpp
@@ -530,6 +530,10 @@ const Symbol *SymbolCollector::addDeclaration(const NamedDecl &ND,
           getTokenLocation(Loc, SM, Opts, ASTCtx->getLangOpts(), FileURI))
     S.CanonicalDeclaration = *DeclLoc;
 
+  S.Origin = Opts.Origin;
+  if (ND.getAvailability() == AR_Deprecated)
+    S.Flags |= Symbol::Deprecated;
+
   // Add completion info.
   // FIXME: we may want to choose a different redecl, or combine from several.
   assert(ASTCtx && PP.get() && "ASTContext and Preprocessor must be set.");
@@ -539,13 +543,28 @@ const Symbol *SymbolCollector::addDeclaration(const NamedDecl &ND,
       *ASTCtx, *PP, CodeCompletionContext::CCC_Symbol, *CompletionAllocator,
       *CompletionTUInfo,
       /*IncludeBriefComments*/ false);
-  std::string Signature;
-  std::string SnippetSuffix;
-  getSignature(*CCS, &Signature, &SnippetSuffix);
   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)) {
+    Symbols.insert(S);
+    return Symbols.find(S.ID);
+  }
+
+  std::string Signature;
+  std::string SnippetSuffix;
+  getSignature(*CCS, &Signature, &SnippetSuffix);
+  S.Signature = Signature;
+  S.CompletionSnippetSuffix = SnippetSuffix;
   std::string ReturnType = getReturnType(*CCS);
+  S.ReturnType = ReturnType;
 
   std::string Include;
   if (Opts.CollectIncludePath && shouldCollectIncludePath(S.SymInfo.Kind)) {
@@ -555,10 +574,6 @@ const Symbol *SymbolCollector::addDeclaration(const NamedDecl &ND,
             QName, SM, SM.getExpansionLoc(ND.getLocation()), Opts))
       Include = std::move(*Header);
   }
-  S.Signature = Signature;
-  S.CompletionSnippetSuffix = SnippetSuffix;
-  S.Documentation = Documentation;
-  S.ReturnType = ReturnType;
   if (!Include.empty())
     S.IncludeHeaders.emplace_back(Include, 1);
 
@@ -569,9 +584,6 @@ const Symbol *SymbolCollector::addDeclaration(const NamedDecl &ND,
       S.Type = TypeStorage->raw();
   }
 
-  S.Origin = Opts.Origin;
-  if (ND.getAvailability() == AR_Deprecated)
-    S.Flags |= Symbol::Deprecated;
   Symbols.insert(S);
   return Symbols.find(S.ID);
 }
diff --git a/unittests/clangd/SymbolCollectorTests.cpp b/unittests/clangd/SymbolCollectorTests.cpp
index a1996fc7..ea84461c 100644
--- a/unittests/clangd/SymbolCollectorTests.cpp
+++ b/unittests/clangd/SymbolCollectorTests.cpp
@@ -654,10 +654,15 @@ TEST_F(SymbolCollectorTest, ClassMembers) {
     void Foo::ssf() {}
   )";
   runSymbolCollector(Header, Main);
-  EXPECT_THAT(Symbols,
-              UnorderedElementsAre(QName("Foo"), QName("Foo::f"),
-                                   QName("Foo::g"), QName("Foo::sf"),
-                                   QName("Foo::ssf"), QName("Foo::x")));
+  EXPECT_THAT(
+      Symbols,
+      UnorderedElementsAre(
+          QName("Foo"),
+          AllOf(QName("Foo::f"), ReturnType(""), ForCodeCompletion(false)),
+          AllOf(QName("Foo::g"), ReturnType(""), ForCodeCompletion(false)),
+          AllOf(QName("Foo::sf"), ReturnType(""), ForCodeCompletion(false)),
+          AllOf(QName("Foo::ssf"), ReturnType(""), ForCodeCompletion(false)),
+          AllOf(QName("Foo::x"), ReturnType(""), ForCodeCompletion(false))));
 }
 
 TEST_F(SymbolCollectorTest, Scopes) {