From 41104a9406dd284d984f7bee30c7756fcfe2b59e Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu@gmail.com>
Date: Mon, 11 Nov 2019 10:34:29 +0100
Subject: [PATCH] [clangd] Fix a regression of not showing documentation from
 forward declarations.

Summary:
There is a regression from https://reviews.llvm.org/D68467. Unlike class
forward declarations, function ducomentation is written in the declaration in
headers, the function definition doesn't contain any documentation, cases like:

```
foo.h
// this is foo.
void foo();
foo.cc

void foo() {}
```
we should still show documentation from the foo declaration.

Reviewers: ilya-biryukov

Reviewed By: ilya-biryukov

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

Tags: #clang

Differential Revision: https://reviews.llvm.org/D69961
---
 clang-tools-extra/clangd/index/Merge.cpp         | 16 +++++++++++-----
 .../clangd/unittests/IndexTests.cpp              | 11 +++++++++--
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/clang-tools-extra/clangd/index/Merge.cpp b/clang-tools-extra/clangd/index/Merge.cpp
index 76c5955893e4..0c9d0c8d3b12 100644
--- a/clang-tools-extra/clangd/index/Merge.cpp
+++ b/clang-tools-extra/clangd/index/Merge.cpp
@@ -186,11 +186,17 @@ Symbol mergeSymbol(const Symbol &L, const Symbol &R) {
     S.Signature = O.Signature;
   if (S.CompletionSnippetSuffix == "")
     S.CompletionSnippetSuffix = O.CompletionSnippetSuffix;
-  // Don't accept documentation from bare forward declarations, if there is a
-  // definition and it didn't provide one. S is often an undocumented class,
-  // and O is a non-canonical forward decl preceded by an irrelevant comment.
-  if (S.Documentation == "" && !S.Definition)
-    S.Documentation = O.Documentation;
+  if (S.Documentation == "") {
+    // Don't accept documentation from bare forward class declarations, if there
+    // is a definition and it didn't provide one. S is often an undocumented
+    // class, and O is a non-canonical forward decl preceded by an irrelevant
+    // comment.
+    bool IsClass = S.SymInfo.Kind == index::SymbolKind::Class ||
+                   S.SymInfo.Kind == index::SymbolKind::Struct ||
+                   S.SymInfo.Kind == index::SymbolKind::Union;
+    if (!IsClass || !S.Definition)
+      S.Documentation = O.Documentation;
+  }
   if (S.ReturnType == "")
     S.ReturnType = O.ReturnType;
   if (S.Type == "")
diff --git a/clang-tools-extra/clangd/unittests/IndexTests.cpp b/clang-tools-extra/clangd/unittests/IndexTests.cpp
index 9f0265d4190a..e868828d7868 100644
--- a/clang-tools-extra/clangd/unittests/IndexTests.cpp
+++ b/clang-tools-extra/clangd/unittests/IndexTests.cpp
@@ -408,13 +408,20 @@ TEST(MergeIndexTest, Refs) {
 }
 
 TEST(MergeIndexTest, NonDocumentation) {
+  using index::SymbolKind;
   Symbol L, R;
   L.ID = R.ID = SymbolID("x");
   L.Definition.FileURI = "file:/x.h";
   R.Documentation = "Forward declarations because x.h is too big to include";
+  for (auto ClassLikeKind :
+       {SymbolKind::Class, SymbolKind::Struct, SymbolKind::Union}) {
+    L.SymInfo.Kind = ClassLikeKind;
+    EXPECT_EQ(mergeSymbol(L, R).Documentation, "");
+  }
 
-  Symbol M = mergeSymbol(L, R);
-  EXPECT_EQ(M.Documentation, "");
+  L.SymInfo.Kind = SymbolKind::Function;
+  R.Documentation = "Documentation from non-class symbols should be included";
+  EXPECT_EQ(mergeSymbol(L, R).Documentation, R.Documentation);
 }
 
 MATCHER_P2(IncludeHeaderWithRef, IncludeHeader, References, "") {