[clangd] Support returning a limited number of completion results.

[sammccall]

Summary

All results are scored, we only process CodeCompletionStrings for the winners.
We now return CompletionList rather than CompletionItem[] (both are valid).
sortText is now based on CodeCompletionResult::orderedName (mostly the same).

This is the first clangd-only completion option, so plumbing changed.
It requires a small clangd patch (exposing CodeCompletionResult::orderedName).

(This can't usefully be enabled yet: we don't support server-side filtering)

[sammccall]

Oops, sorting was backwards (test caught it, but I forgot to run it)

[ilya-biryukov]

LGTM

clangd/ClangdLSPServer.cpp

if (!Edits.empty()) {
           {"arguments", {WE}},
       });
     }
   }
   C.reply(std::move(Commands));
 }
 
 void ClangdLSPServer::onCompletion(Ctx C, TextDocumentPositionParams &Params) {
-  auto Items = Server
-                   .codeComplete(Params.textDocument.uri.file,
-                                 Position{Params.position.line,
-                                          Params.position.character})
-                   .get() // FIXME(ibiryukov): This could be made async if we
-                          // had an API that would allow to attach callbacks to
-                          // futures returned by ClangdServer.
-                   .Value;
-  C.reply(json::ary(Items));
+  auto List = Server
+                  .codeComplete(
+                      Params.textDocument.uri.file,
+                      Position{Params.position.line, Params.position.character})
+  C.reply(List);
 }
 
 void ClangdLSPServer::onSignatureHelp(Ctx C,
                                       TextDocumentPositionParams &Params) {
   auto SignatureHelp = Server.signatureHelp(
       Params.textDocument.uri.file,
       Position{Params.position.line, Params.position.character});
   if (!SignatureHelp)

clangd/ClangdServer.h

public:
   /// completion, i.e. no diagnostics update will be scheduled and a draft for
   /// \p File will not be updated. If \p OverridenContents is None, contents of
   /// the current draft for \p File will be used. If \p UsedFS is non-null, it
   /// will be overwritten by vfs::FileSystem used for completion.
   ///
   /// This method should only be called for currently tracked files. However, it
   /// is safe to call removeDocument for \p File after this method returns, even
   /// while returned future is not yet ready.
-  std::future<Tagged<std::vector<CompletionItem>>>
+  std::future<Tagged<CompletionList>>
   codeComplete(PathRef File, Position Pos,
                llvm::Optional<StringRef> OverridenContents = llvm::None,
                IntrusiveRefCntPtr<vfs::FileSystem> *UsedFS = nullptr);
 
   /// A version of `codeComplete` that runs \p Callback on the processing thread
   /// when codeComplete results become available.
-  void codeComplete(
-      UniqueFunction<void(Tagged<std::vector<CompletionItem>>)> Callback,
+  void codeComplete(UniqueFunction<void(Tagged<CompletionList>)> Callback,
                     PathRef File, Position Pos,
                     llvm::Optional<StringRef> OverridenContents = llvm::None,
                     IntrusiveRefCntPtr<vfs::FileSystem> *UsedFS = nullptr);
 
   /// Provide signature help for \p File at \p Pos. If \p OverridenContents is
   /// not None, they will used only for signature help, i.e. no diagnostics
   /// update will be scheduled and a draft for \p File will not be updated. If
   /// \p OverridenContents is None, contents of the current draft for \p File
   /// will be used. If \p UsedFS is non-null, it will be overwritten by
   /// vfs::FileSystem used for signature help. This method should only be called
   /// for currently tracked files.

clangd/ClangdServer.cpp

std::future<void> ClangdServer::forceReparse(PathRef File) {
   // Note that std::future from this cleanup action is ignored.
   scheduleCancelRebuild(std::move(Recreated.RemovedFile));
   // Schedule a reparse.
   return scheduleReparseAndDiags(File, std::move(FileContents),
                                  std::move(Recreated.FileInCollection),
                                  std::move(TaggedFS));
 }
 
-std::future<Tagged<std::vector<CompletionItem>>>
+std::future<Tagged<CompletionList>>
 ClangdServer::codeComplete(PathRef File, Position Pos,
                            llvm::Optional<StringRef> OverridenContents,
                            IntrusiveRefCntPtr<vfs::FileSystem> *UsedFS) {
-  using ResultType = Tagged<std::vector<CompletionItem>>;
+  using ResultType = Tagged<CompletionList>;
 
   std::promise<ResultType> ResultPromise;
 
   auto Callback = [](std::promise<ResultType> ResultPromise,
                      ResultType Result) -> void {
     ResultPromise.set_value(std::move(Result));
   };
 
   std::future<ResultType> ResultFuture = ResultPromise.get_future();
   codeComplete(BindWithForward(Callback, std::move(ResultPromise)), File, Pos,
                OverridenContents, UsedFS);
   return ResultFuture;
 }
 
 void ClangdServer::codeComplete(
-    UniqueFunction<void(Tagged<std::vector<CompletionItem>>)> Callback,
-    PathRef File, Position Pos, llvm::Optional<StringRef> OverridenContents,
+    UniqueFunction<void(Tagged<CompletionList>)> Callback, PathRef File,
+    Position Pos, llvm::Optional<StringRef> OverridenContents,
     IntrusiveRefCntPtr<vfs::FileSystem> *UsedFS) {
-  using CallbackType =
-      UniqueFunction<void(Tagged<std::vector<CompletionItem>>)>;
+  using CallbackType = UniqueFunction<void(Tagged<CompletionList>)>;
 
   std::string Contents;
   if (OverridenContents) {
     Contents = *OverridenContents;
   } else {
     auto FileContents = DraftMgr.getDraft(File);
     assert(FileContents.Draft &&
            "codeComplete is called for non-added document");
auto Task =
       [=](CallbackType Callback) mutable {
         if (!Preamble) {
           // Maybe we built some preamble before processing this request.
           Preamble = Resources->getPossiblyStalePreamble();
         }
         // FIXME(ibiryukov): even if Preamble is non-null, we may want to check
         // both the old and the new version in case only one of them matches.
 
-        std::vector<CompletionItem> Result = clangd::codeComplete(
+        CompletionList Result = clangd::codeComplete(
             File, Resources->getCompileCommand(),
             Preamble ? &Preamble->Preamble : nullptr, Contents, Pos,
             TaggedFS.Value, PCHs, CodeCompleteOpts, Logger);
 
         Callback(make_tagged(std::move(Result), std::move(TaggedFS.Tag)));
       };
 
   WorkScheduler.addToFront(std::move(Task), std::move(Callback));

clangd/ClangdUnit.h

struct CodeCompleteOptions {
   /// IncludeCodePatterns to the value of EnableSnippetsAndCodePatterns.
   explicit CodeCompleteOptions(bool EnableSnippetsAndCodePatterns);
 
   CodeCompleteOptions(bool EnableSnippets, bool IncludeCodePatterns,
                       bool IncludeMacros, bool IncludeGlobals,
                       bool IncludeBriefComments);
 
   /// Returns options that can be passed to clang's completion engine.
-  clang::CodeCompleteOptions getClangCompleteOpts();
+  clang::CodeCompleteOptions getClangCompleteOpts() const;
 
   /// When true, completion items will contain expandable code snippets in
   /// completion (e.g.  `return ${1:expression}` or `foo(${1:int a}, ${2:int
   /// b})).
   bool EnableSnippets = false;
 
   /// Add code patterns to completion results.
   /// If EnableSnippets is false, this options is ignored and code patterns will
   /// always be omitted.
   bool IncludeCodePatterns = false;
 
   /// Add macros to code completion results.
   bool IncludeMacros = true;
 
   /// Add globals to code completion results.
   bool IncludeGlobals = true;
 
   /// Add brief comments to completion items, if available.
   /// FIXME(ibiryukov): it looks like turning this option on significantly slows
   /// down completion, investigate if it can be made faster.
   bool IncludeBriefComments = true;
+
+  /// Limit the number of results returned (0 means no limit).
+  /// If more results are available, we set CompletionList.isIncomplete.
+  size_t Limit = 0;
 };
 
 /// Get code completions at a specified \p Pos in \p FileName.
-std::vector<CompletionItem>
+CompletionList
 codeComplete(PathRef FileName, const tooling::CompileCommand &Command,
              PrecompiledPreamble const *Preamble, StringRef Contents,
              Position Pos, IntrusiveRefCntPtr<vfs::FileSystem> VFS,
              std::shared_ptr<PCHContainerOperations> PCHs,
              clangd::CodeCompleteOptions Opts, clangd::Logger &Logger);
 
 /// Get signature help at a specified \p Pos in \p FileName.
 SignatureHelp signatureHelp(PathRef FileName,

clangd/ClangdUnit.cpp

if (!Result.empty()) {
       // character to make the annotations stand out.
       Result.push_back('\n');
     }
     Result += CCS.getBriefComment();
   }
   return Result;
 }
 
+/// A scored code completion result.
+/// It may be promoted to a CompletionItem if it's among the top-ranked results.
+struct CompletionCandidate {
+  CompletionCandidate(CodeCompletionResult &Result)
+      : Result(&Result), Score(score(Result)) {}
+
+  CodeCompletionResult *Result;
+  // Higher score is worse. FIXME: use a more natural scale!
+  int Score;
+
+  // Comparison reflects rank: better candidates are smaller.
+  bool operator<(const CompletionCandidate &C) const {
+    if (Score != C.Score)
+      return Score < C.Score;
+    return *Result < *C.Result;
+  }
+
+  std::string sortText() const {
+    // Fill in the sortText of the CompletionItem.
+    assert(Score <= 999999 && "Expecting score to have at most 6-digits");
+    std::string S, NameStorage;
+    StringRef Name = Result->orderedName(NameStorage);
+    llvm::raw_string_ostream(S)
+        << llvm::format("%06d%.*s", Score, Name.size(), Name.data());
+    return S;
+  }
+
+private:
+  static int score(const CodeCompletionResult &Result) {
+    int Score = Result.Priority;
+    // Fill in the sortText of the CompletionItem.
+    assert(Score <= 99999 && "Expecting code completion result "
+                             "priority to have at most 5-digits");
+
+    const int Penalty = 100000;
+    switch (static_cast<CXAvailabilityKind>(Result.Availability)) {
+    case CXAvailability_Available:
+      // No penalty.
+      break;
+    case CXAvailability_Deprecated:
+      Score += Penalty;
+      break;
+    case CXAvailability_NotAccessible:
+      Score += 2 * Penalty;
+      break;
+    case CXAvailability_NotAvailable:
+      Score += 3 * Penalty;
+      break;
+    }
+    return Score;
+  }
+};
+
 class CompletionItemsCollector : public CodeCompleteConsumer {
 public:
-  CompletionItemsCollector(const clang::CodeCompleteOptions &CodeCompleteOpts,
-                           std::vector<CompletionItem> &Items)
-      : CodeCompleteConsumer(CodeCompleteOpts, /*OutputIsBinary=*/false),
-        Items(Items),
+  CompletionItemsCollector(const clangd::CodeCompleteOptions &CodeCompleteOpts,
+                           CompletionList &Items)
+      : CodeCompleteConsumer(CodeCompleteOpts.getClangCompleteOpts(),
+                             /*OutputIsBinary=*/false),
+        ClangdOpts(CodeCompleteOpts), Items(Items),
         Allocator(std::make_shared<clang::GlobalCodeCompletionAllocator>()),
         CCTUInfo(Allocator) {}
 
   void ProcessCodeCompleteResults(Sema &S, CodeCompletionContext Context,
                                   CodeCompletionResult *Results,
                                   unsigned NumResults) override final {
-    Items.reserve(NumResults);
+    std::priority_queue<CompletionCandidate> Candidates;
     for (unsigned I = 0; I < NumResults; ++I) {
-      auto &Result = Results[I];
-      const auto *CCS = Result.CreateCodeCompletionString(
+      Candidates.emplace(Results[I]);
+      if (ClangdOpts.Limit && Candidates.size() > ClangdOpts.Limit) {
+        Candidates.pop();
+        Items.isIncomplete = true;
+      }
+    }
+    while (!Candidates.empty()) {
+      auto &Candidate = Candidates.top();
+      const auto *CCS = Candidate.Result->CreateCodeCompletionString(
           S, Context, *Allocator, CCTUInfo,
           CodeCompleteOpts.IncludeBriefComments);
       assert(CCS && "Expected the CodeCompletionString to be non-null");
-      Items.push_back(ProcessCodeCompleteResult(Result, *CCS));
+      Items.items.push_back(ProcessCodeCompleteResult(Candidate, *CCS));
+      Candidates.pop();
     }
-    std::sort(Items.begin(), Items.end());
+    std::reverse(Items.items.begin(), Items.items.end());
   }
 
   GlobalCodeCompletionAllocator &getAllocator() override { return *Allocator; }
 
   CodeCompletionTUInfo &getCodeCompletionTUInfo() override { return CCTUInfo; }
 
 private:
   CompletionItem
-  ProcessCodeCompleteResult(const CodeCompletionResult &Result,
+  ProcessCodeCompleteResult(const CompletionCandidate &Candidate,
                             const CodeCompletionString &CCS) const {
 
     // Adjust this to InsertTextFormat::Snippet iff we encounter a
     // CK_Placeholder chunk in SnippetCompletionItemsCollector.
     CompletionItem Item;
     Item.insertTextFormat = InsertTextFormat::PlainText;
 
     Item.documentation = getDocumentation(CCS);
+    Item.sortText = Candidate.sortText();
 
     // Fill in the label, detail, insertText and filterText fields of the
     // CompletionItem.
     ProcessChunks(CCS, Item);
 
     // Fill in the kind field of the CompletionItem.
-    Item.kind = getKind(Result.Kind, Result.CursorKind);
-
-    FillSortText(CCS, Item);
+    Item.kind = getKind(Candidate.Result->Kind, Candidate.Result->CursorKind);
 
     return Item;
   }
 
   virtual void ProcessChunks(const CodeCompletionString &CCS,
                              CompletionItem &Item) const = 0;
 
-  static int GetSortPriority(const CodeCompletionString &CCS) {
-    int Score = CCS.getPriority();
-    // Fill in the sortText of the CompletionItem.
-    assert(Score <= 99999 && "Expecting code completion result "
-                             "priority to have at most 5-digits");
-
-    const int Penalty = 100000;
-    switch (static_cast<CXAvailabilityKind>(CCS.getAvailability())) {
-    case CXAvailability_Available:
-      // No penalty.
-      break;
-    case CXAvailability_Deprecated:
-      Score += Penalty;
-      break;
-    case CXAvailability_NotAccessible:
-      Score += 2 * Penalty;
-      break;
-    case CXAvailability_NotAvailable:
-      Score += 3 * Penalty;
-      break;
-    }
-
-    return Score;
-  }
-
-  static void FillSortText(const CodeCompletionString &CCS,
-                           CompletionItem &Item) {
-    int Priority = GetSortPriority(CCS);
-    // Fill in the sortText of the CompletionItem.
-    assert(Priority <= 999999 &&
-           "Expecting sort priority to have at most 6-digits");
-    llvm::raw_string_ostream(Item.sortText)
-        << llvm::format("%06d%s", Priority, Item.filterText.c_str());
-  }
-
-  std::vector<CompletionItem> &Items;
+  clangd::CodeCompleteOptions ClangdOpts;
+  CompletionList &Items;
   std::shared_ptr<clang::GlobalCodeCompletionAllocator> Allocator;
   CodeCompletionTUInfo CCTUInfo;
 
 }; // CompletionItemsCollector
 
 bool isInformativeQualifierChunk(CodeCompletionString::Chunk const &Chunk) {
   return Chunk.Kind == CodeCompletionString::CK_Informative &&
          StringRef(Chunk.Text).endswith("::");
 }
 
 class PlainTextCompletionItemsCollector final
     : public CompletionItemsCollector {
 
 public:
   PlainTextCompletionItemsCollector(
-      const clang::CodeCompleteOptions &CodeCompleteOpts,
-      std::vector<CompletionItem> &Items)
+      const clangd::CodeCompleteOptions &CodeCompleteOpts,
+      CompletionList &Items)
       : CompletionItemsCollector(CodeCompleteOpts, Items) {}
 
 private:
   void ProcessChunks(const CodeCompletionString &CCS,
                      CompletionItem &Item) const override {
     for (const auto &Chunk : CCS) {
       // Informative qualifier chunks only clutter completion results, skip
       // them.
void ProcessChunks(const CodeCompletionString &CCS,
     }
   }
 }; // PlainTextCompletionItemsCollector
 
 class SnippetCompletionItemsCollector final : public CompletionItemsCollector {
 
 public:
   SnippetCompletionItemsCollector(
-      const clang::CodeCompleteOptions &CodeCompleteOpts,
-      std::vector<CompletionItem> &Items)
+      const clangd::CodeCompleteOptions &CodeCompleteOpts,
+      CompletionList &Items)
       : CompletionItemsCollector(CodeCompleteOpts, Items) {}
 
 private:
   void ProcessChunks(const CodeCompletionString &CCS,
                      CompletionItem &Item) const override {
     unsigned ArgCount = 0;
     for (const auto &Chunk : CCS) {
       // Informative qualifier chunks only clutter completion results, skip
clangd::CodeCompleteOptions::CodeCompleteOptions(bool EnableSnippets,
                                                  bool IncludeCodePatterns,
                                                  bool IncludeMacros,
                                                  bool IncludeGlobals,
                                                  bool IncludeBriefComments)
     : EnableSnippets(EnableSnippets), IncludeCodePatterns(IncludeCodePatterns),
       IncludeMacros(IncludeMacros), IncludeGlobals(IncludeGlobals),
       IncludeBriefComments(IncludeBriefComments) {}
 
-clang::CodeCompleteOptions clangd::CodeCompleteOptions::getClangCompleteOpts() {
+clang::CodeCompleteOptions
+clangd::CodeCompleteOptions::getClangCompleteOpts() const {
   clang::CodeCompleteOptions Result;
   Result.IncludeCodePatterns = EnableSnippets && IncludeCodePatterns;
   Result.IncludeMacros = IncludeMacros;
   Result.IncludeGlobals = IncludeGlobals;
   Result.IncludeBriefComments = IncludeBriefComments;
 
   return Result;
 }
 
-std::vector<CompletionItem>
+CompletionList
 clangd::codeComplete(PathRef FileName, const tooling::CompileCommand &Command,
                      PrecompiledPreamble const *Preamble, StringRef Contents,
                      Position Pos, IntrusiveRefCntPtr<vfs::FileSystem> VFS,
                      std::shared_ptr<PCHContainerOperations> PCHs,
                      clangd::CodeCompleteOptions Opts, clangd::Logger &Logger) {
-  std::vector<CompletionItem> Results;
+  CompletionList Results;
   std::unique_ptr<CodeCompleteConsumer> Consumer;
-  clang::CodeCompleteOptions ClangCompleteOpts = Opts.getClangCompleteOpts();
   if (Opts.EnableSnippets) {
-    Consumer = llvm::make_unique<SnippetCompletionItemsCollector>(
-        ClangCompleteOpts, Results);
+    Consumer =
+        llvm::make_unique<SnippetCompletionItemsCollector>(Opts, Results);
   } else {
-    Consumer = llvm::make_unique<PlainTextCompletionItemsCollector>(
-        ClangCompleteOpts, Results);
+    Consumer =
+        llvm::make_unique<PlainTextCompletionItemsCollector>(Opts, Results);
   }
-  invokeCodeComplete(std::move(Consumer), ClangCompleteOpts, FileName, Command,
-                     Preamble, Contents, Pos, std::move(VFS), std::move(PCHs),
-                     Logger);
+  invokeCodeComplete(std::move(Consumer), Opts.getClangCompleteOpts(), FileName,
+                     Command, Preamble, Contents, Pos, std::move(VFS),
+                     std::move(PCHs), Logger);
   return Results;
 }
 
 SignatureHelp
 clangd::signatureHelp(PathRef FileName, const tooling::CompileCommand &Command,
                       PrecompiledPreamble const *Preamble, StringRef Contents,
                       Position Pos, IntrusiveRefCntPtr<vfs::FileSystem> VFS,
                       std::shared_ptr<PCHContainerOperations> PCHs,

clangd/Protocol.h

struct CompletionItem {
   //
   // data?: any - A data entry field that is preserved on a completion item
   //              between a completion and a completion resolve request.
   static json::Expr unparse(const CompletionItem &P);
 };
 
 bool operator<(const CompletionItem &, const CompletionItem &);
 
+/// Represents a collection of completion items to be presented in the editor.
+struct CompletionList {
+  /// The list is not complete. Further typing should result in recomputing the
+  /// list.
+  bool isIncomplete = false;
+
+  /// The completion items.
+  std::vector<CompletionItem> items;
+
+  static json::Expr unparse(const CompletionList &);
+};
+
 /// A single parameter of a particular signature.
 struct ParameterInformation {
 
   /// The label of this parameter. Mandatory.
   std::string label;
 
   /// The documentation of this parameter. Optional.
   std::string documentation;

clangd/Protocol.cpp

json::Expr CompletionItem::unparse(const CompletionItem &CI) {
   return std::move(Result);
 }
 
 bool clangd::operator<(const CompletionItem &L, const CompletionItem &R) {
   return (L.sortText.empty() ? L.label : L.sortText) <
          (R.sortText.empty() ? R.label : R.sortText);
 }
 
+json::Expr CompletionList::unparse(const CompletionList &L) {
+  return json::obj{
+      {"isIncomplete", L.isIncomplete},
+      {"items", json::ary(L.items)},
+  };
+}
+
 json::Expr ParameterInformation::unparse(const ParameterInformation &PI) {
   assert(!PI.label.empty() && "parameter information label is required");
   json::obj Result{{"label", PI.label}};
   if (!PI.documentation.empty())
     Result["documentation"] = PI.documentation;
   return std::move(Result);
 }
 

test/clangd/authority-less-uri.test

 
 Content-Length: 146
 
 {"jsonrpc":"2.0","id":1,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:/main.cpp"},"position":{"line":3,"character":5}}}
 # Test authority-less URI
 #
 #      CHECK:  "id": 1,
 # CHECK-NEXT:  "jsonrpc": "2.0",
-# CHECK-NEXT:  "result": [
-#      CHECK:      "filterText": "fake",
-# CHECK-NEXT:      "insertText": "fake",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 7,
-# CHECK-NEXT:      "label": "fake::",
-# CHECK-NEXT:      "sortText": "000075fake"
-#      CHECK:  ]
+# CHECK-NEXT:  "result": {
+# CHECK-NEXT:    "isIncomplete": false,
+# CHECK-NEXT:    "items": [
+#      CHECK:        "filterText": "fake",
+# CHECK-NEXT:        "insertText": "fake",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 7,
+# CHECK-NEXT:        "label": "fake::",
+# CHECK-NEXT:        "sortText": "000075fake"
+#      CHECK:    ]
+# CHECK-NEXT:  }
 Content-Length: 172
 
 {"jsonrpc":"2.0","id":2,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:///main.cpp"},"uri":"file:///main.cpp","position":{"line":3,"character":5}}}
 # Test params parsing in the presence of a 1.x-compatible client (inlined "uri")
 #
 #      CHECK:  "id": 2,
 # CHECK-NEXT:  "jsonrpc": "2.0",
-# CHECK-NEXT:  "result": [
-#      CHECK:      "filterText": "fake",
-# CHECK-NEXT:      "insertText": "fake",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 7,
-# CHECK-NEXT:      "label": "fake::",
-# CHECK-NEXT:      "sortText": "000075fake"
-#      CHECK:  ]
+# CHECK-NEXT:  "result": {
+# CHECK-NEXT:    "isIncomplete": false,
+# CHECK-NEXT:    "items": [
+#      CHECK:        "filterText": "fake",
+# CHECK-NEXT:        "insertText": "fake",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 7,
+# CHECK-NEXT:        "label": "fake::",
+# CHECK-NEXT:        "sortText": "000075fake"
+#      CHECK:    ]
+# CHECK-NEXT:  }
 Content-Length: 44
 
 {"jsonrpc":"2.0","id":3,"method":"shutdown"}
 Content-Length: 33
 
 {"jsonrpc":"2.0":"method":"exit"}

test/clangd/completion-items-kinds.test

 # RUN: clangd -enable-snippets -run-synchronously < %s | FileCheck %s
 # It is absolutely vital that this file has CRLF line endings.
 #
 Content-Length: 125
 
 {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{},"trace":"off"}}
 Content-Length: 220
 
 {"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"file:///main.cpp","languageId":"cpp","version":1,"text":"#define MACRO X\nint variable;\nstruct Struct {};\n int function();\nint X = "}}}
 Content-Length: 148
 
 {"jsonrpc":"2.0","id":1,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:///main.cpp"},"position":{"line":4,"character":7}}}
 Content-Length: 58
-# CHECK: {"id":1,"jsonrpc":"2.0","result":[
+# CHECK: {"id":1,"jsonrpc":"2.0","result":{"isIncomplete":false,"items":
 #
 # Keyword
 # CHECK-DAG: {"filterText":"int","insertText":"int","insertTextFormat":1,"kind":14,"label":"int","sortText":"000050int"}
 #
 # Code pattern
 # CHECK-DAG: {"filterText":"static_cast","insertText":"static_cast<${1:type}>(${2:expression})","insertTextFormat":2,"kind":15,"label":"static_cast<type>(expression)","sortText":"000040static_cast"}
 #
 # Struct
 # CHECK-DAG: {"filterText":"Struct","insertText":"Struct","insertTextFormat":1,"kind":7,"label":"Struct","sortText":"000050Struct"}
 #
 # Macro
 # CHECK-DAG: {"filterText":"MACRO","insertText":"MACRO","insertTextFormat":1,"kind":1,"label":"MACRO","sortText":"000070MACRO"}
 #
 # Variable
 # CHECK-DAG: {"detail":"int","filterText":"variable","insertText":"variable","insertTextFormat":1,"kind":6,"label":"variable","sortText":"000012variable"}
 #
 # Function
 # CHECK-DAG: {"detail":"int","filterText":"function","insertText":"function()","insertTextFormat":1,"kind":3,"label":"function()","sortText":"000012function"}
 #
-# CHECK-SAME: ]}
+# CHECK-SAME: ]}}
 
 {"jsonrpc":"2.0","id":3,"method":"shutdown","params":null}

test/clangd/completion-priorities.test

 
 {"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"file:///main.cpp","languageId":"cpp","version":1,"text":"class Foo {\npublic:\n  void pub();\n\nprotected:\n  void prot();\n\nprivate:\n  void priv();\n};\n\nvoid Foo::pub() {\n  this->\n}\n\nvoid test() {\n  Foo f;\n  f.\n}"}}}
 
 Content-Length: 151
 
 {"jsonrpc":"2.0","id":2,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:///main.cpp"},"position":{"line":12,"character":8}}}
 #      CHECK:  "id": 2,
 # CHECK-NEXT:  "jsonrpc": "2.0",
-# CHECK-NEXT:  "result": [
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "detail": "void",
-# CHECK-NEXT:      "filterText": "priv",
-# CHECK-NEXT:      "insertText": "priv",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 2,
-# CHECK-NEXT:      "label": "priv()",
-# CHECK-NEXT:      "sortText": "000034priv"
-# CHECK-NEXT:    },
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "detail": "void",
-# CHECK-NEXT:      "filterText": "prot",
-# CHECK-NEXT:      "insertText": "prot",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 2,
-# CHECK-NEXT:      "label": "prot()",
-# CHECK-NEXT:      "sortText": "000034prot"
-# CHECK-NEXT:    },
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "detail": "void",
-# CHECK-NEXT:      "filterText": "pub",
-# CHECK-NEXT:      "insertText": "pub",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 2,
-# CHECK-NEXT:      "label": "pub()",
-# CHECK-NEXT:      "sortText": "000034pub"
-# CHECK-NEXT:    },
+# CHECK-NEXT:  "result": {
+# CHECK-NEXT:    "isIncomplete": false,
+# CHECK-NEXT:    "items": [
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "detail": "void",
+# CHECK-NEXT:        "filterText": "priv",
+# CHECK-NEXT:        "insertText": "priv",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 2,
+# CHECK-NEXT:        "label": "priv()",
+# CHECK-NEXT:        "sortText": "000034priv"
+# CHECK-NEXT:      },
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "detail": "void",
+# CHECK-NEXT:        "filterText": "prot",
+# CHECK-NEXT:        "insertText": "prot",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 2,
+# CHECK-NEXT:        "label": "prot()",
+# CHECK-NEXT:        "sortText": "000034prot"
+# CHECK-NEXT:      },
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "detail": "void",
+# CHECK-NEXT:        "filterText": "pub",
+# CHECK-NEXT:        "insertText": "pub",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 2,
+# CHECK-NEXT:        "label": "pub()",
+# CHECK-NEXT:        "sortText": "000034pub"
+# CHECK-NEXT:      },
 Content-Length: 151
 
 {"jsonrpc":"2.0","id":3,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:///main.cpp"},"position":{"line":17,"character":4}}}
 #      CHECK:  "id": 3,
 # CHECK-NEXT:  "jsonrpc": "2.0",
-# CHECK-NEXT:  "result": [
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "detail": "void",
-# CHECK-NEXT:      "filterText": "pub",
-# CHECK-NEXT:      "insertText": "pub",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 2,
-# CHECK-NEXT:      "label": "pub()",
-# CHECK-NEXT:      "sortText": "000034pub"
-# CHECK-NEXT:    },
+# CHECK-NEXT:  "result": {
+# CHECK-NEXT:    "isIncomplete": false,
+# CHECK-NEXT:    "items": [
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "detail": "void",
+# CHECK-NEXT:        "filterText": "pub",
+# CHECK-NEXT:        "insertText": "pub",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 2,
+# CHECK-NEXT:        "label": "pub()",
+# CHECK-NEXT:        "sortText": "000034pub"
+# CHECK-NEXT:      },
 # priv() and prot() are at the end of the list
-# CHECK-NEXT:    {
-#      CHECK:      "detail": "void",
-#      CHECK:      "filterText": "priv",
-# CHECK-NEXT:      "insertText": "priv",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 2,
-# CHECK-NEXT:      "label": "priv()",
-# CHECK-NEXT:      "sortText": "200034priv"
-# CHECK-NEXT:    },
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "detail": "void",
-# CHECK-NEXT:      "filterText": "prot",
-# CHECK-NEXT:      "insertText": "prot",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 2,
-# CHECK-NEXT:      "label": "prot()",
-# CHECK-NEXT:      "sortText": "200034prot"
-# CHECK-NEXT:    }
-# CHECK-NEXT:  ]
+# CHECK-NEXT:      {
+#      CHECK:        "detail": "void",
+#      CHECK:        "filterText": "priv",
+# CHECK-NEXT:        "insertText": "priv",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 2,
+# CHECK-NEXT:        "label": "priv()",
+# CHECK-NEXT:        "sortText": "200034priv"
+# CHECK-NEXT:      },
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "detail": "void",
+# CHECK-NEXT:        "filterText": "prot",
+# CHECK-NEXT:        "insertText": "prot",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 2,
+# CHECK-NEXT:        "label": "prot()",
+# CHECK-NEXT:        "sortText": "200034prot"
+# CHECK-NEXT:      }
+# CHECK-NEXT:    ]
+# CHECK-NEXT:  }
 Content-Length: 58
 
 {"jsonrpc":"2.0","id":4,"method":"shutdown","params":null}
 Content-Length: 33
 
 {"jsonrpc":"2.0":"method":"exit"}

test/clangd/completion-qualifiers.test

 # RUN: clangd -pretty -run-synchronously < %s | FileCheck -strict-whitespace %s
 Content-Length: 125
 
 {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{},"trace":"off"}}
 Content-Length: 297
 
 {"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"file:///main.cpp","languageId":"cpp","version":1,"text":"class Foo {\n  public:\n    int foo() const;\n    int bar() const;\n};\n\nclass Bar : public Foo {\n  int foo() const;\n};\n\nvoid test() {\n  Bar().\n}"}}}
 Content-Length: 151
 
 {"jsonrpc":"2.0","id":2,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:///main.cpp"},"position":{"line":11,"character":8}}}
 #      CHECK:  "id": 2,
 # CHECK-NEXT:  "jsonrpc": "2.0",
-# CHECK-NEXT:  "result": [
+# CHECK-NEXT:  "result": {
+# CHECK-NEXT:    "isIncomplete": false,
+# CHECK-NEXT:    "items": [
 # Eligible const functions are at the top of the list.
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "detail": "int",
-# CHECK-NEXT:      "filterText": "bar",
-# CHECK-NEXT:      "insertText": "bar",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 2,
-# CHECK-NEXT:      "label": "bar() const",
-# CHECK-NEXT:      "sortText": "000037bar"
-# CHECK-NEXT:    },
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "detail": "int",
-# CHECK-NEXT:      "filterText": "foo",
-# CHECK-NEXT:      "insertText": "foo",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 2,
-# CHECK-NEXT:      "label": "Foo::foo() const",
-# CHECK-NEXT:      "sortText": "000037foo"
-# CHECK-NEXT:    },
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "detail": "int",
+# CHECK-NEXT:        "filterText": "bar",
+# CHECK-NEXT:        "insertText": "bar",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 2,
+# CHECK-NEXT:        "label": "bar() const",
+# CHECK-NEXT:        "sortText": "000037bar"
+# CHECK-NEXT:      },
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "detail": "int",
+# CHECK-NEXT:        "filterText": "foo",
+# CHECK-NEXT:        "insertText": "foo",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 2,
+# CHECK-NEXT:        "label": "Foo::foo() const",
+# CHECK-NEXT:        "sortText": "000037foo"
+# CHECK-NEXT:      },
 # Ineligible non-const function is at the bottom of the list.
-# CHECK-NEXT:    {
-#      CHECK:      "detail": "int",
-#      CHECK:      "filterText": "foo",
-# CHECK-NEXT:      "insertText": "foo",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 2,
-# CHECK-NEXT:      "label": "foo() const",
-# CHECK-NEXT:      "sortText": "200035foo"
-# CHECK-NEXT:    }
-# CHECK-NEXT:  ]
+# CHECK-NEXT:      {
+#      CHECK:        "detail": "int",
+#      CHECK:        "filterText": "foo",
+# CHECK-NEXT:        "insertText": "foo",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 2,
+# CHECK-NEXT:        "label": "foo() const",
+# CHECK-NEXT:        "sortText": "200035foo"
+# CHECK-NEXT:      }
+# CHECK-NEXT:    ]
+# CHECK-NEXT:  }
 Content-Length: 44
 
 {"jsonrpc":"2.0","id":4,"method":"shutdown"}
 Content-Length: 33
 
 {"jsonrpc":"2.0":"method":"exit"}

test/clangd/completion-snippet.test

 # RUN: clangd -pretty -run-synchronously -enable-snippets < %s | FileCheck -strict-whitespace %s
 # It is absolutely vital that this file has CRLF line endings.
 #
 Content-Length: 125
 
 {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{},"trace":"off"}}
 
 Content-Length: 246
 
 {"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"file:///main.cpp","languageId":"cpp","version":1,"text":"struct fake { int a, bb, ccc; int f(int i, const float f) const; };\nint main() {\n  fake f;\n  f.\n}\n"}}}
 
 Content-Length: 148
 
 {"jsonrpc":"2.0","id":1,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:///main.cpp"},"position":{"line":3,"character":5}}}
 #      CHECK:  "id": 1,
 # CHECK-NEXT:  "jsonrpc": "2.0",
-# CHECK-NEXT:  "result": [
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "detail": "int",
-# CHECK-NEXT:      "filterText": "a",
-# CHECK-NEXT:      "insertText": "a",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 5,
-# CHECK-NEXT:      "label": "a",
-# CHECK-NEXT:      "sortText": "000035a"
-# CHECK-NEXT:    },
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "detail": "int",
-# CHECK-NEXT:      "filterText": "bb",
-# CHECK-NEXT:      "insertText": "bb",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 5,
-# CHECK-NEXT:      "label": "bb",
-# CHECK-NEXT:      "sortText": "000035bb"
-# CHECK-NEXT:    },
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "detail": "int",
-# CHECK-NEXT:      "filterText": "ccc",
-# CHECK-NEXT:      "insertText": "ccc",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 5,
-# CHECK-NEXT:      "label": "ccc",
-# CHECK-NEXT:      "sortText": "000035ccc"
-# CHECK-NEXT:    },
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "detail": "int",
-# CHECK-NEXT:      "filterText": "f",
-# CHECK-NEXT:      "insertText": "f(${1:int i}, ${2:const float f})",
-# CHECK-NEXT:      "insertTextFormat": 2,
-# CHECK-NEXT:      "kind": 2,
-# CHECK-NEXT:      "label": "f(int i, const float f) const",
-# CHECK-NEXT:      "sortText": "000035f"
-# CHECK-NEXT:    },
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "filterText": "fake",
-# CHECK-NEXT:      "insertText": "fake::",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 7,
-# CHECK-NEXT:      "label": "fake::",
-# CHECK-NEXT:      "sortText": "000075fake"
-# CHECK-NEXT:    },
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "detail": "fake &",
-# CHECK-NEXT:      "filterText": "operator=",
-# CHECK-NEXT:      "insertText": "operator=(${1:const fake &})",
-# CHECK-NEXT:      "insertTextFormat": 2,
-# CHECK-NEXT:      "kind": 2,
-# CHECK-NEXT:      "label": "operator=(const fake &)",
-# CHECK-NEXT:      "sortText": "000079operator="
-# CHECK-NEXT:    },
+# CHECK-NEXT:  "result": {
+# CHECK-NEXT:    "isIncomplete": false,
+# CHECK-NEXT:    "items": [
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "detail": "int",
+# CHECK-NEXT:        "filterText": "a",
+# CHECK-NEXT:        "insertText": "a",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 5,
+# CHECK-NEXT:        "label": "a",
+# CHECK-NEXT:        "sortText": "000035a"
+# CHECK-NEXT:      },
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "detail": "int",
+# CHECK-NEXT:        "filterText": "bb",
+# CHECK-NEXT:        "insertText": "bb",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 5,
+# CHECK-NEXT:        "label": "bb",
+# CHECK-NEXT:        "sortText": "000035bb"
+# CHECK-NEXT:      },
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "detail": "int",
+# CHECK-NEXT:        "filterText": "ccc",
+# CHECK-NEXT:        "insertText": "ccc",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 5,
+# CHECK-NEXT:        "label": "ccc",
+# CHECK-NEXT:        "sortText": "000035ccc"
+# CHECK-NEXT:      },
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "detail": "int",
+# CHECK-NEXT:        "filterText": "f",
+# CHECK-NEXT:        "insertText": "f(${1:int i}, ${2:const float f})",
+# CHECK-NEXT:        "insertTextFormat": 2,
+# CHECK-NEXT:        "kind": 2,
+# CHECK-NEXT:        "label": "f(int i, const float f) const",
+# CHECK-NEXT:        "sortText": "000035f"
+# CHECK-NEXT:      },
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "filterText": "fake",
+# CHECK-NEXT:        "insertText": "fake::",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 7,
+# CHECK-NEXT:        "label": "fake::",
+# CHECK-NEXT:        "sortText": "000075fake"
+# CHECK-NEXT:      },
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "detail": "fake &",
+# CHECK-NEXT:        "filterText": "operator=",
+# CHECK-NEXT:        "insertText": "operator=(${1:const fake &})",
+# CHECK-NEXT:        "insertTextFormat": 2,
+# CHECK-NEXT:        "kind": 2,
+# CHECK-NEXT:        "label": "operator=(const fake &)",
+# CHECK-NEXT:        "sortText": "000079operator="
+# CHECK-NEXT:      },
 # FIXME: Why do some buildbots show an extra operator==(fake&&) here?
-#      CHECK:    {
-#      CHECK:      "detail": "void",
-# CHECK-NEXT:      "filterText": "~fake",
-# CHECK-NEXT:      "insertText": "~fake()",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 4,
-# CHECK-NEXT:      "label": "~fake()",
-# CHECK-NEXT:      "sortText": "000079~fake"
-# CHECK-NEXT:    }
-# CHECK-NEXT:  ]
+#      CHECK:      {
+#      CHECK:        "detail": "void",
+# CHECK-NEXT:        "filterText": "~fake",
+# CHECK-NEXT:        "insertText": "~fake()",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 4,
+# CHECK-NEXT:        "label": "~fake()",
+# CHECK-NEXT:        "sortText": "000079~fake"
+# CHECK-NEXT:      }
+# CHECK-NEXT:    ]
+# CHECK-NEXT:  }
 # Update the source file and check for completions again.
 Content-Length: 226
 
 {"jsonrpc":"2.0","method":"textDocument/didChange","params":{"textDocument":{"uri":"file:///main.cpp","version":2},"contentChanges":[{"text":"struct fancy { int (*func())(int, int); };\nint main() {\n  fancy f;\n  f.\n}\n"}]}}
 
 Content-Length: 148
 
 {"jsonrpc":"2.0","id":3,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:///main.cpp"},"position":{"line":3,"character":5}}}
 #      CHECK:  "id": 3,
 # CHECK-NEXT:  "jsonrpc": "2.0",
-# CHECK-NEXT:  "result": [
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "detail": "int (*)(int, int)",
-# CHECK-NEXT:      "filterText": "func",
-# CHECK-NEXT:      "insertText": "func()",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 2,
-# CHECK-NEXT:      "label": "func()",
-# CHECK-NEXT:      "sortText": "000034func"
-# CHECK-NEXT:    },
+# CHECK-NEXT:  "result": {
+# CHECK-NEXT:    "isIncomplete": false,
+# CHECK-NEXT:    "items": [
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "detail": "int (*)(int, int)",
+# CHECK-NEXT:        "filterText": "func",
+# CHECK-NEXT:        "insertText": "func()",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 2,
+# CHECK-NEXT:        "label": "func()",
+# CHECK-NEXT:        "sortText": "000034func"
+# CHECK-NEXT:      },
 Content-Length: 44
 
 {"jsonrpc":"2.0","id":4,"method":"shutdown"}
 Content-Length: 33
 
 {"jsonrpc":"2.0":"method":"exit"}

test/clangd/completion.test

 # RUN: clangd -pretty -run-synchronously < %s | FileCheck -strict-whitespace %s
 # It is absolutely vital that this file has CRLF line endings.
 #
 Content-Length: 125
 
 {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{},"trace":"off"}}
 
 Content-Length: 246
 
 {"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"file:///main.cpp","languageId":"cpp","version":1,"text":"struct fake { int a, bb, ccc; int f(int i, const float f) const; };\nint main() {\n  fake f;\n  f.\n}\n"}}}
 
 Content-Length: 148
 
 {"jsonrpc":"2.0","id":1,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:///main.cpp"},"position":{"line":3,"character":5}}}
 #      CHECK:  "id": 1
 # CHECK-NEXT:  "jsonrpc": "2.0",
-# CHECK-NEXT:  "result": [
+# CHECK-NEXT:  "result": {
+# CHECK-NEXT:    "isIncomplete": false,
+# CHECK-NEXT:    "items": [
 # CHECK-NEXT:    {
 # CHECK-NEXT:      "detail": "int",
 # CHECK-NEXT:      "filterText": "a",
 # CHECK-NEXT:      "insertText": "a",
 # CHECK-NEXT:      "insertTextFormat": 1,
 # CHECK-NEXT:      "kind": 5,
 # CHECK-NEXT:      "label": "a",
 # CHECK-NEXT:      "sortText": "000035a"

 # CHECK-NEXT:      "sortText": "000079~fake"
 # CHECK-NEXT:    }
 # CHECK-NEXT:  ]
 Content-Length: 148
 
 {"jsonrpc":"2.0","id":2,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:///main.cpp"},"position":{"line":3,"character":5}}}
 #      CHECK:  "id": 2
 # CHECK-NEXT:  "jsonrpc": "2.0",
-# CHECK-NEXT:  "result": [
+# CHECK-NEXT:  "result": {
+# CHECK-NEXT:    "isIncomplete": false,
+# CHECK-NEXT:    "items": [
 # CHECK-NEXT:    {
 # CHECK-NEXT:      "detail": "int",
 # CHECK-NEXT:      "filterText": "a",
 # CHECK-NEXT:      "insertText": "a",
 # CHECK-NEXT:      "insertTextFormat": 1,
 # CHECK-NEXT:      "kind": 5,
 # CHECK-NEXT:      "label": "a",
 # CHECK-NEXT:      "sortText": "000035a"

 
 {"jsonrpc":"2.0","method":"textDocument/didChange","params":{"textDocument":{"uri":"file:///main.cpp","version":2},"contentChanges":[{"text":"struct fancy { int (*func())(int, int); };\nint main() {\n  fancy f;\n  f.\n}\n"}]}}
 
 Content-Length: 148
 
 {"jsonrpc":"2.0","id":3,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:///main.cpp"},"position":{"line":3,"character":5}}}
 #      CHECK:    "id": 3,
 # CHECK-NEXT:  "jsonrpc": "2.0",
-# CHECK-NEXT:  "result": [
+# CHECK-NEXT:  "result": {
+# CHECK-NEXT:    "isIncomplete": false,
+# CHECK-NEXT:    "items": [
 # CHECK-NEXT:    {
 # CHECK-NEXT:      "detail": "int (*)(int, int)",
 # CHECK-NEXT:      "filterText": "func",
 # CHECK-NEXT:      "insertText": "func",
 # CHECK-NEXT:      "insertTextFormat": 1,
 # CHECK-NEXT:      "kind": 2,
 # CHECK-NEXT:      "label": "func()",
 # CHECK-NEXT:      "sortText": "000034func"

test/clangd/protocol.test

 Content-Type: application/vscode-jsonrpc; charset-utf-8
 Content-Length: 146
 
 {"jsonrpc":"2.0","id":1,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:/main.cpp"},"position":{"line":3,"character":5}}}
 # Test message with Content-Type before Content-Length
 #
 #      CHECK:  "id": 1,
 # CHECK-NEXT:  "jsonrpc": "2.0",
-# CHECK-NEXT:  "result": [
-#      CHECK:      "filterText": "fake",
-# CHECK-NEXT:      "insertText": "fake",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 7,
-# CHECK-NEXT:      "label": "fake::",
-# CHECK-NEXT:      "sortText": "000075fake"
-#      CHECK:  ]
+# CHECK-NEXT:  "result": {
+# CHECK-NEXT:    "isIncomplete": false,
+# CHECK-NEXT:    "items": [
+#      CHECK:        "filterText": "fake",
+# CHECK-NEXT:        "insertText": "fake",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 7,
+# CHECK-NEXT:        "label": "fake::",
+# CHECK-NEXT:        "sortText": "000075fake"
+#      CHECK:    ]
+# CHECK-NEXT:  }
 
 X-Test: Testing
 Content-Type: application/vscode-jsonrpc; charset-utf-8
 Content-Length: 146
 Content-Type: application/vscode-jsonrpc; charset-utf-8
 X-Testing: Test
 
 {"jsonrpc":"2.0","id":2,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:/main.cpp"},"position":{"line":3,"character":5}}}
 
 Content-Type: application/vscode-jsonrpc; charset-utf-8
 Content-Length: 10
 Content-Length: 146
 
 {"jsonrpc":"2.0","id":3,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:/main.cpp"},"position":{"line":3,"character":5}}}
 # Test message with duplicate Content-Length headers
 #
 #      CHECK:  "id": 3,
 # CHECK-NEXT:  "jsonrpc": "2.0",
-# CHECK-NEXT:  "result": [
-#      CHECK:      "filterText": "fake",
-# CHECK-NEXT:      "insertText": "fake",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 7,
-# CHECK-NEXT:      "label": "fake::",
-# CHECK-NEXT:      "sortText": "000075fake"
-#      CHECK:  ]
+# CHECK-NEXT:  "result": {
+# CHECK-NEXT:    "isIncomplete": false,
+# CHECK-NEXT:    "items": [
+#      CHECK:        "filterText": "fake",
+# CHECK-NEXT:        "insertText": "fake",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 7,
+# CHECK-NEXT:        "label": "fake::",
+# CHECK-NEXT:        "sortText": "000075fake"
+#      CHECK:    ]
+# CHECK-NEXT:  }
 # STDERR: Warning: Duplicate Content-Length header received. The previous value for this message (10) was ignored.
 
 Content-Type: application/vscode-jsonrpc; charset-utf-8
 Content-Length: 10
 
 {"jsonrpc":"2.0","id":4,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:/main.cpp"},"position":{"line":3,"character":5}}}
 # Test message with malformed Content-Length
 #
 # STDERR: JSON dispatch failed!
 # Ensure we recover by sending another (valid) message
 
 Content-Length: 146
 
 {"jsonrpc":"2.0","id":5,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:/main.cpp"},"position":{"line":3,"character":5}}}
 # Test message with Content-Type before Content-Length
 #
 #      CHECK:  "id": 5,
 # CHECK-NEXT:  "jsonrpc": "2.0",
-# CHECK-NEXT:  "result": [
-#      CHECK:      "filterText": "fake",
-# CHECK-NEXT:      "insertText": "fake",
-# CHECK-NEXT:      "insertTextFormat": 1,
-# CHECK-NEXT:      "kind": 7,
-# CHECK-NEXT:      "label": "fake::",
-# CHECK-NEXT:      "sortText": "000075fake"
-#      CHECK:  ]
+# CHECK-NEXT:  "result": {
+# CHECK-NEXT:    "isIncomplete": false,
+# CHECK-NEXT:    "items": [
+#      CHECK:        "filterText": "fake",
+# CHECK-NEXT:        "insertText": "fake",
+# CHECK-NEXT:        "insertTextFormat": 1,
+# CHECK-NEXT:        "kind": 7,
+# CHECK-NEXT:        "label": "fake::",
+# CHECK-NEXT:        "sortText": "000075fake"
+#      CHECK:    ]
+# CHECK-NEXT:  }
 Content-Length: 1024
 
 {"jsonrpc":"2.0","id":5,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:/main.cpp"},"position":{"line":3,"character":5}}}
 # Test message which reads beyond the end of the stream.
 #
 # Ensure this is the last test in the file!
 # STDERR: Input was aborted. Read only {{[0-9]+}} bytes of expected {{[0-9]+}}.
 

unittests/clangd/ClangdTests.cpp

)cpp";
   EXPECT_FALSE(DiagConsumer.hadErrorInLastDiags());
   Server.addDocument(FooCpp, SourceContents2);
   EXPECT_FALSE(DiagConsumer.hadErrorInLastDiags());
 }
 
 class ClangdCompletionTest : public ClangdVFSTest {
 protected:
   template <class Predicate>
-  bool ContainsItemPred(std::vector<CompletionItem> const &Items,
-                        Predicate Pred) {
-    for (const auto &Item : Items) {
+  bool ContainsItemPred(CompletionList const &Items, Predicate Pred) {
+    for (const auto &Item : Items.items) {
       if (Pred(Item))
         return true;
     }
     return false;
   }
 
-  bool ContainsItem(std::vector<CompletionItem> const &Items, StringRef Name) {
+  bool ContainsItem(CompletionList const &Items, StringRef Name) {
     return ContainsItemPred(Items, [Name](clangd::CompletionItem Item) {
       return Item.insertText == Name;
     });
     return false;
   }
 };
 
 TEST_F(ClangdCompletionTest, CheckContentsOverride) {
)cpp";
   {
     auto CodeCompletionResults2 =
         Server.codeComplete(FooCpp, CompletePos, None).get().Value;
     EXPECT_TRUE(ContainsItem(CodeCompletionResults2, "aba"));
     EXPECT_FALSE(ContainsItem(CodeCompletionResults2, "cbc"));
   }
 }
 
+TEST_F(ClangdCompletionTest, Limit) {
+  MockFSProvider FS;
+  MockCompilationDatabase CDB(/*AddFreestandingFlag=*/true);
+  CDB.ExtraClangFlags.push_back("-xc++");
+  ErrorCheckingDiagConsumer DiagConsumer;
+  clangd::CodeCompleteOptions Opts;
+  Opts.Limit = 2;
+  ClangdServer Server(CDB, DiagConsumer, FS, getDefaultAsyncThreadsCount(),
+                      Opts, EmptyLogger::getInstance());
+
+  auto FooCpp = getVirtualTestFilePath("foo.cpp");
+  FS.Files[FooCpp] = "";
+  FS.ExpectedFile = FooCpp;
+  StringWithPos Completion = parseTextMarker(R"cpp(
+struct ClassWithMembers {
+  int AAA();
+  int BBB();
+  int CCC();
+}
+int main() { ClassWithMembers().{complete} }
+      )cpp",
+                                             "complete");
+  Server.addDocument(FooCpp, Completion.Text);
+
+  /// For after-dot completion we must always get consistent results.
+  auto Results = Server
+                     .codeComplete(FooCpp, Completion.MarkerPos,
+                                   StringRef(Completion.Text))
+                     .get()
+                     .Value;
+
+  EXPECT_TRUE(Results.isIncomplete);
+  EXPECT_EQ(Opts.Limit, Results.items.size());
+  EXPECT_TRUE(ContainsItem(Results, "AAA"));
+  EXPECT_TRUE(ContainsItem(Results, "BBB"));
+  EXPECT_FALSE(ContainsItem(Results, "CCC"));
+}
+
 TEST_F(ClangdCompletionTest, CompletionOptions) {
   MockFSProvider FS;
   ErrorCheckingDiagConsumer DiagConsumer;
   MockCompilationDatabase CDB(/*AddFreestandingFlag=*/true);
   CDB.ExtraClangFlags.push_back("-xc++");
 
   auto FooCpp = getVirtualTestFilePath("foo.cpp");
   FS.Files[FooCpp] = "";