[clangd] Do not report comments that only have special chars.

Summary:
Like the following:
  // -------
  // =======
  // *******

It does not cover all the cases, but those are definitely not very
useful.

Reviewers: sammccall, ioeric, hokein

Reviewed By: sammccall

Subscribers: MaskRay, jkorous, cfe-commits

Differential Revision: https://reviews.llvm.org/D48171

2 files changed, 77 insertions, 2 deletions

diff --git a/clang-tools-extra/clangd/CodeCompletionStrings.cpp b/clang-tools-extra/clangd/CodeCompletionStrings.cpp
index 8cdaa3380b8..c3066939a5a 100644
--- a/clang-tools-extra/clangd/CodeCompletionStrings.cpp
+++ b/clang-tools-extra/clangd/CodeCompletionStrings.cpp
@@ -151,6 +151,16 @@ bool canRequestComment(const ASTContext &Ctx, const NamedDecl &D,
   const ObjCPropertyDecl *PDecl = M ? M->findPropertyDecl() : nullptr;
   return !PDecl || canRequestForDecl(*PDecl);
 }
+
+bool LooksLikeDocComment(llvm::StringRef CommentText) {
+  // We don't report comments that only contain "special" chars.
+  // This avoids reporting various delimiters, like:
+  //   =================
+  //   -----------------
+  //   *****************
+  return CommentText.find_first_not_of("/*-= \t\r\n") != llvm::StringRef::npos;
+}
+
 } // namespace
 
 std::string getDocComment(const ASTContext &Ctx,
@@ -167,7 +177,10 @@ std::string getDocComment(const ASTContext &Ctx,
   const RawComment *RC = getCompletionComment(Ctx, Decl);
   if (!RC)
     return "";
-  return RC->getFormattedText(Ctx.getSourceManager(), Ctx.getDiagnostics());
+  std::string Doc = RC->getFormattedText(Ctx.getSourceManager(), Ctx.getDiagnostics());
+  if (!LooksLikeDocComment(Doc))
+    return "";
+  return Doc;
 }
 
 std::string
@@ -180,7 +193,10 @@ getParameterDocComment(const ASTContext &Ctx,
   const RawComment *RC = getParameterComment(Ctx, Result, ArgIndex);
   if (!RC)
     return "";
-  return RC->getFormattedText(Ctx.getSourceManager(), Ctx.getDiagnostics());
+  std::string Doc = RC->getFormattedText(Ctx.getSourceManager(), Ctx.getDiagnostics());
+  if (!LooksLikeDocComment(Doc))
+    return "";
+  return Doc;
 }
 
 void getLabelAndInsertText(const CodeCompletionString &CCS, std::string *Label,
diff --git a/clang-tools-extra/unittests/clangd/CodeCompleteTests.cpp b/clang-tools-extra/unittests/clangd/CodeCompleteTests.cpp
index 534b554fcfa..5f22fe9385a 100644
--- a/clang-tools-extra/unittests/clangd/CodeCompleteTests.cpp
+++ b/clang-tools-extra/unittests/clangd/CodeCompleteTests.cpp
@@ -1100,6 +1100,65 @@ TEST(CompletionTest, DocumentationFromChangedFileCrash) {
               Contains(AllOf(Not(IsDocumented()), Named("func"))));
 }
 
+TEST(CompletionTest, NonDocComments) {
+  MockFSProvider FS;
+  auto FooCpp = testPath("foo.cpp");
+  FS.Files[FooCpp] = "";
+
+  MockCompilationDatabase CDB;
+  IgnoreDiagnostics DiagConsumer;
+  ClangdServer Server(CDB, FS, DiagConsumer, ClangdServer::optsForTest());
+
+  Annotations Source(R"cpp(
+    // ------------------
+    int comments_foo();
+
+    // A comment and a decl are separated by newlines.
+    // Therefore, the comment shouldn't show up as doc comment.
+
+    int comments_bar();
+
+    // this comment should be in the results.
+    int comments_baz();
+
+
+    template <class T>
+    struct Struct {
+      int comments_qux();
+      int comments_quux();
+    };
+
+
+    // This comment should not be there.
+
+    template <class T>
+    int Struct<T>::comments_qux() {
+    }
+
+    // This comment **should** be in results.
+    template <class T>
+    int Struct<T>::comments_quux() {
+      int a = comments^;
+    }
+  )cpp");
+  Server.addDocument(FooCpp, Source.code(), WantDiagnostics::Yes);
+  CompletionList Completions = cantFail(runCodeComplete(
+      Server, FooCpp, Source.point(), clangd::CodeCompleteOptions()));
+
+  // We should not get any of those comments in completion.
+  EXPECT_THAT(
+      Completions.items,
+      UnorderedElementsAre(AllOf(Not(IsDocumented()), Named("comments_foo")),
+                           AllOf(IsDocumented(), Named("comments_baz")),
+                           AllOf(IsDocumented(), Named("comments_quux")),
+                           // FIXME(ibiryukov): the following items should have
+                           // empty documentation, since they are separated from
+                           // a comment with an empty line. Unfortunately, I
+                           // couldn't make Sema tests pass if we ignore those.
+                           AllOf(IsDocumented(), Named("comments_bar")),
+                           AllOf(IsDocumented(), Named("comments_qux"))));
+}
+
 TEST(CompletionTest, CompleteOnInvalidLine) {
   auto FooCpp = testPath("foo.cpp");