First iteration of code completion off the main thread. Still one race condition but hopefully it shouldn't happen too often.

src/atomic_object.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <algorithm>
+#include <condition_variable>
+#include <memory>
+#include <mutex>
+
+
+// A object which can be stored and taken from atomically.
+template <class T>
+struct AtomicObject {
+  void Set(std::unique_ptr<T> t) {
+    std::lock_guard<std::mutex> lock(mutex_);
+    value_ = std::move(t);
+    cv_.notify_one();
+  }
+
+  std::unique_ptr<T> Take() {
+    std::unique_lock<std::mutex> lock(mutex_);
+    while (!value_) {
+      // release lock as long as the wait and reaquire it afterwards.
+      cv_.wait(lock);
+    }
+    
+    return std::move(value_);
+  }
+
+ private:
+  std::unique_ptr<T> value_;
+  mutable std::mutex mutex_;
+  std::condition_variable cv_;
+};

src/code_completion.cc

@@ -4,6 +4,7 @@
 #include "timer.h"
 
 #include <algorithm>
+#include <thread>
 
 namespace {
 unsigned Flags() {
@@ -191,64 +192,28 @@ std::string BuildDetailString(CXCompletionString completion_string) {
 
   return detail;
 }
-}
 
-CompletionSession::CompletionSession(const CompilationEntry& file, WorkingFiles* working_files) : file(file) {
-  std::vector<CXUnsavedFile> unsaved = working_files->AsUnsavedFiles();
+void CompletionMain(CompletionManager* completion_manager) {
+  while (true) {
+    std::unique_ptr<CompletionManager::CompletionRequest> request = completion_manager->completion_request.Take();
 
-  std::vector<std::string> args = file.args;
-  args.push_back("-x");
-  args.push_back("c++");
-  args.push_back("-fparse-all-comments");
 
-  std::string sent_args = "";
-  for (auto& arg : args)
-    sent_args += arg + ", ";
-  std::cerr << "Creating completion session with arguments " << sent_args << std::endl;
-
-  // TODO: I think we crash when there are syntax errors.
-  active_index = MakeUnique<clang::Index>(0 /*excludeDeclarationsFromPCH*/, 0 /*displayDiagnostics*/);
-  active = MakeUnique<clang::TranslationUnit>(*active_index, file.filename, args, unsaved, Flags());
-  std::cerr << "Done creating active; did_fail=" << active->did_fail << std::endl;
-  //if (active->did_fail) {
-  //  std::cerr << "Failed to create translation unit; trying again..." << std::endl;
-  //  active = MakeUnique<clang::TranslationUnit>(*active_index, file.filename, args, unsaved, Flags());
-  //}
-
-  // Despite requesting clang create a precompiled header on the first parse in
-  // Flags() via CXTranslationUnit_CreatePreambleOnFirstParse, it doesn't seem
-  // to do so. Immediately reparsing will create one which reduces
-  // clang_codeCompleteAt timing from 200ms to 20ms on simple files.
-  // TODO: figure out why this is crashing so much
-  if (!active->did_fail) {
-    std::cerr << "Start reparse" << std::endl;
-    active->ReparseTranslationUnit(unsaved);
-
-    std::cerr << "Done reparse" << std::endl;
-  }
-}
-
-CompletionSession::~CompletionSession() {}
-
-void CompletionSession::Refresh(std::vector<CXUnsavedFile>& unsaved) {
-  // TODO: Do this off the code completion thread so we don't block completions.
-  active->ReparseTranslationUnit(unsaved);
-}
-
-CompletionManager::CompletionManager(Project* project, WorkingFiles* working_files) : project(project), working_files(working_files) {}
-
-NonElidedVector<lsCompletionItem> CompletionManager::CodeComplete(const lsTextDocumentPositionParams& completion_location) {
     NonElidedVector<lsCompletionItem> ls_result;
 
-  CompletionSession* session = GetOrOpenSession(completion_location.textDocument.uri.GetPath());
+    CompletionSession* session = completion_manager->GetOrOpenSession(request->location.textDocument.uri.GetPath());
 
-  unsigned line = completion_location.position.line + 1;
-  unsigned column = completion_location.position.character + 1;
+    unsigned line = request->location.position.line + 1;
+    unsigned column = request->location.position.character + 1;
 
     std::cerr << std::endl;
-  //std::cerr << "Completing at " << line << ":" << column << std::endl;
+    std::cerr << "Completing at " << line << ":" << column << std::endl;
 
-  std::vector<CXUnsavedFile> unsaved = working_files->AsUnsavedFiles();
+    // TODO/FIXME
+    // TODO/FIXME
+    // TODO/FIXME NOT THREAD SAFE
+    // TODO/FIXME
+    // TODO/FIXME
+    std::vector<CXUnsavedFile> unsaved = completion_manager->working_files->AsUnsavedFiles();
 
 
     Timer timer;
@@ -262,7 +227,8 @@ NonElidedVector<lsCompletionItem> CompletionManager::CodeComplete(const lsTextDo
       CXCodeComplete_IncludeMacros | CXCodeComplete_IncludeBriefComments);
     if (!cx_results) {
       std::cerr << "Code completion failed" << std::endl;
-    return ls_result;
+      request->on_complete(ls_result);
+      continue;
     }
     timer.ResetAndPrint("clangCodeCompleteAt");
     std::cerr << "Got " << cx_results->NumResults << " results" << std::endl;
@@ -323,12 +289,13 @@ NonElidedVector<lsCompletionItem> CompletionManager::CodeComplete(const lsTextDo
 
       ls_result.push_back(ls_completion_item);
     }
-  timer.ResetAndPrint("Building completion results");
+    timer.ResetAndPrint("Building " + std::to_string(ls_result.size()) + " completion results");
 
     clang_disposeCodeCompleteResults(cx_results);
     timer.ResetAndPrint("clang_disposeCodeCompleteResults ");
 
-  return ls_result;
+    request->on_complete(ls_result);
+    continue;
 
     // we should probably main two translation units, one for
     // serving current requests, and one that is reparsing (follow qtcreator)
@@ -353,6 +320,64 @@ NonElidedVector<lsCompletionItem> CompletionManager::CodeComplete(const lsTextDo
     // probably don't need
     //  - textDocument/willSave
   }
+}
+
+}  // namespace
+
+CompletionSession::CompletionSession(const CompilationEntry& file, WorkingFiles* working_files) : file(file) {
+  std::vector<CXUnsavedFile> unsaved = working_files->AsUnsavedFiles();
+
+  std::vector<std::string> args = file.args;
+  args.push_back("-x");
+  args.push_back("c++");
+  args.push_back("-fparse-all-comments");
+
+  std::string sent_args = "";
+  for (auto& arg : args)
+    sent_args += arg + ", ";
+  std::cerr << "Creating completion session with arguments " << sent_args << std::endl;
+
+  // TODO: I think we crash when there are syntax errors.
+  active_index = MakeUnique<clang::Index>(0 /*excludeDeclarationsFromPCH*/, 0 /*displayDiagnostics*/);
+  active = MakeUnique<clang::TranslationUnit>(*active_index, file.filename, args, unsaved, Flags());
+  std::cerr << "Done creating active; did_fail=" << active->did_fail << std::endl;
+  //if (active->did_fail) {
+  //  std::cerr << "Failed to create translation unit; trying again..." << std::endl;
+  //  active = MakeUnique<clang::TranslationUnit>(*active_index, file.filename, args, unsaved, Flags());
+  //}
+
+  // Despite requesting clang create a precompiled header on the first parse in
+  // Flags() via CXTranslationUnit_CreatePreambleOnFirstParse, it doesn't seem
+  // to do so. Immediately reparsing will create one which reduces
+  // clang_codeCompleteAt timing from 200ms to 20ms on simple files.
+  // TODO: figure out why this is crashing so much
+  if (!active->did_fail) {
+    std::cerr << "Start reparse" << std::endl;
+    active->ReparseTranslationUnit(unsaved);
+
+    std::cerr << "Done reparse" << std::endl;
+  }
+}
+
+CompletionSession::~CompletionSession() {}
+
+void CompletionSession::Refresh(std::vector<CXUnsavedFile>& unsaved) {
+  // TODO: Do this off the code completion thread so we don't block completions.
+  active->ReparseTranslationUnit(unsaved);
+}
+
+CompletionManager::CompletionManager(Project* project, WorkingFiles* working_files) : project(project), working_files(working_files) {
+  new std::thread([&]() {
+    CompletionMain(this);
+  });
+}
+
+void CompletionManager::CodeComplete(const lsTextDocumentPositionParams& completion_location, const OnComplete& on_complete) {
+  auto request = MakeUnique<CompletionRequest>();
+  request->location = completion_location;
+  request->on_complete = on_complete;
+  completion_request.Set(std::move(request));
+}
 
 CompletionSession* CompletionManager::GetOrOpenSession(const std::string& filename) {
   // Try to find existing session.

src/code_completion.h

@@ -1,3 +1,4 @@
+#include "atomic_object.h"
 #include "language_server_api.h"
 #include "libclangmm/CompletionString.h"
 #include "libclangmm/Index.h"
@@ -7,6 +8,8 @@
 
 #include <clang-c/Index.h>
 
+#include <functional>
+
 struct CompletionSession {
   CompilationEntry file;
 
@@ -33,12 +36,18 @@ struct CompletionManager {
   Project* project;
   WorkingFiles* working_files;
 
+  using OnComplete = std::function<void(NonElidedVector<lsCompletionItem> results)>;
+  struct CompletionRequest {
+    lsTextDocumentPositionParams location;
+    OnComplete on_complete;
+  };
+  AtomicObject<CompletionRequest> completion_request;
+
   CompletionManager(Project* project, WorkingFiles* working_files);
 
-  // This all should run on complete_responder thread. This will internally run a child thread to
-  // reparse.
-  NonElidedVector<lsCompletionItem> CodeComplete(const lsTextDocumentPositionParams& completion_location);
+  // Start a code completion at the given location. |on_complete| will run when
+  // completion results are available. |on_complete| may run on any thread.
+  void CodeComplete(const lsTextDocumentPositionParams& completion_location, const OnComplete& on_complete);
 
- private:
   CompletionSession* GetOrOpenSession(const std::string& filename);
 };

src/command_line.cc

@@ -20,6 +20,7 @@
 #include <rapidjson/ostreamwrapper.h>
 
 #include <fstream>
+#include <functional>
 #include <iostream>
 #include <string>
 #include <unordered_map>
@@ -999,13 +1000,6 @@ void IndexMain(
 
 
 
-
-
-
-
-
-
-
 
 
 
@@ -1170,16 +1164,27 @@ void QueryDbMainLoop(
     }
 
     case IpcId::TextDocumentCompletion: {
-      // TODO: better performance
       auto msg = static_cast<Ipc_TextDocumentComplete*>(message.get());
+      lsTextDocumentPositionParams params = msg->params;
+
+      CompletionManager::OnComplete callback = std::bind([](BaseIpcMessage* message, const NonElidedVector<lsCompletionItem>& results) {
+        auto msg = static_cast<Ipc_TextDocumentComplete*>(message);
+        auto ipc = IpcManager::instance();
+
         Out_TextDocumentComplete response;
         response.id = msg->id;
         response.result.isIncomplete = false;
-      response.result.items = completion_manager->CodeComplete(msg->params);
+        response.result.items = results;
 
         Timer timer;
         ipc->SendOutMessageToClient(response);
         timer.ResetAndPrint("Writing completion results");
+
+        delete message;
+      }, message.release(), std::placeholders::_1);
+
+      completion_manager->CodeComplete(params, std::move(callback));
+
       break;
     }