lib/inc/drogon/utils/coroutine.h

@@ -24,6 +24,7 @@
 #include <exception>
 #include <future>
 #include <mutex>
+#include <list>
 #include <type_traits>
 #include <optional>
 
@@ -83,11 +84,6 @@ struct is_awaitable<
 template <typename T>
 constexpr bool is_awaitable_v = is_awaitable<T>::value;
 
-/**
- * @struct final_awaiter
- * @brief An awaiter for `Task::promise_type::final_suspend()`. Transfer
- * execution back to the coroutine who is co_awaiting this Task.
- */
 struct final_awaiter
 {
     bool await_ready() noexcept
@@ -106,52 +102,6 @@ struct final_awaiter
     }
 };
 
-/**
- * @struct task_awaiter
- * @brief Convert Task to an awaiter when it is co_awaited.
- * Following things will happen:
- * 1. Suspend current coroutine
- * 2. Set current coroutine as continuation of this Task
- * 3. Transfer execution to the co_awaited Task
- */
-template <typename Promise>
-struct task_awaiter
-{
-    using handle_type = std::coroutine_handle<Promise>;
-
-  public:
-    explicit task_awaiter(handle_type coro) : coro_(coro)
-    {
-    }
-
-    bool await_ready() noexcept
-    {
-        return !coro_ || coro_.done();
-    }
-
-    auto await_suspend(std::coroutine_handle<> handle) noexcept
-    {
-        coro_.promise().setContinuation(handle);
-        return coro_;
-    }
-
-    auto await_resume()
-    {
-        if constexpr (std::is_void_v<decltype(coro_.promise().result())>)
-        {
-            coro_.promise().result();  // throw exception if any
-            return;
-        }
-        else
-        {
-            return std::move(coro_.promise().result());
-        }
-    }
-
-  private:
-    handle_type coro_;
-};
-
 template <typename T = void>
 struct [[nodiscard]] Task
 {
@@ -164,7 +114,7 @@ struct [[nodiscard]] Task
 
     Task(const Task &) = delete;
 
-    Task(Task &&other) noexcept
+    Task(Task &&other)
     {
         coro_ = other.coro_;
         other.coro_ = nullptr;
@@ -178,7 +128,7 @@ struct [[nodiscard]] Task
 
     Task &operator=(const Task &) = delete;
 
-    Task &operator=(Task &&other) noexcept
+    Task &operator=(Task &&other)
     {
         if (std::addressof(other) == this)
             return *this;
@@ -248,9 +198,69 @@ struct [[nodiscard]] Task
         std::coroutine_handle<> continuation_;
     };
 
-    auto operator co_await() const noexcept
+    auto operator co_await() const &noexcept
     {
-        return task_awaiter(coro_);
+        struct awaiter
+        {
+          public:
+            explicit awaiter(handle_type coro) : coro_(coro)
+            {
+            }
+
+            bool await_ready() noexcept
+            {
+                return !coro_ || coro_.done();
+            }
+
+            auto await_suspend(std::coroutine_handle<> handle) noexcept
+            {
+                coro_.promise().setContinuation(handle);
+                return coro_;
+            }
+
+            T await_resume()
+            {
+                auto &&v = coro_.promise().result();
+                return std::move(v);
+            }
+
+          private:
+            handle_type coro_;
+        };
+
+        return awaiter(coro_);
+    }
+
+    auto operator co_await() const &&noexcept
+    {
+        struct awaiter
+        {
+          public:
+            explicit awaiter(handle_type coro) : coro_(coro)
+            {
+            }
+
+            bool await_ready() noexcept
+            {
+                return !coro_ || coro_.done();
+            }
+
+            auto await_suspend(std::coroutine_handle<> handle) noexcept
+            {
+                coro_.promise().setContinuation(handle);
+                return coro_;
+            }
+
+            T await_resume()
+            {
+                return std::move(coro_.promise().result());
+            }
+
+          private:
+            handle_type coro_;
+        };
+
+        return awaiter(coro_);
     }
 
     handle_type coro_;
@@ -268,7 +278,7 @@ struct [[nodiscard]] Task<void>
 
     Task(const Task &) = delete;
 
-    Task(Task &&other) noexcept
+    Task(Task &&other)
     {
         coro_ = other.coro_;
         other.coro_ = nullptr;
@@ -282,7 +292,7 @@ struct [[nodiscard]] Task<void>
 
     Task &operator=(const Task &) = delete;
 
-    Task &operator=(Task &&other) noexcept
+    Task &operator=(Task &&other)
     {
         if (std::addressof(other) == this)
             return *this;
@@ -335,9 +345,68 @@ struct [[nodiscard]] Task<void>
         std::coroutine_handle<> continuation_;
     };
 
-    auto operator co_await() const noexcept
+    auto operator co_await() const &noexcept
     {
-        return task_awaiter(coro_);
+        struct awaiter
+        {
+          public:
+            explicit awaiter(handle_type coro) : coro_(coro)
+            {
+            }
+
+            bool await_ready() noexcept
+            {
+                return !coro_ || coro_.done();
+            }
+
+            auto await_suspend(std::coroutine_handle<> handle) noexcept
+            {
+                coro_.promise().setContinuation(handle);
+                return coro_;
+            }
+
+            auto await_resume()
+            {
+                coro_.promise().result();
+            }
+
+          private:
+            handle_type coro_;
+        };
+
+        return awaiter(coro_);
+    }
+
+    auto operator co_await() const &&noexcept
+    {
+        struct awaiter
+        {
+          public:
+            explicit awaiter(handle_type coro) : coro_(coro)
+            {
+            }
+
+            bool await_ready() noexcept
+            {
+                return false;
+            }
+
+            auto await_suspend(std::coroutine_handle<> handle) noexcept
+            {
+                coro_.promise().setContinuation(handle);
+                return coro_;
+            }
+
+            void await_resume()
+            {
+                coro_.promise().result();
+            }
+
+          private:
+            handle_type coro_;
+        };
+
+        return awaiter(coro_);
     }
 
     handle_type coro_;
@@ -360,7 +429,7 @@ struct AsyncTask
 
     AsyncTask(const AsyncTask &) = delete;
 
-    AsyncTask(AsyncTask &&other) noexcept
+    AsyncTask(AsyncTask &&other)
     {
         coro_ = other.coro_;
         other.coro_ = nullptr;
@@ -368,7 +437,7 @@ struct AsyncTask
 
     AsyncTask &operator=(const AsyncTask &) = delete;
 
-    AsyncTask &operator=(AsyncTask &&other) noexcept
+    AsyncTask &operator=(AsyncTask &&other)
     {
         if (std::addressof(other) == this)
             return *this;
@@ -380,6 +449,8 @@ struct AsyncTask
 
     struct promise_type
     {
+        std::coroutine_handle<> continuation_;
+
         AsyncTask get_return_object() noexcept
         {
             return {std::coroutine_handle<promise_type>::from_promise(*this)};
@@ -400,12 +471,51 @@ struct AsyncTask
         {
         }
 
-        std::suspend_never final_suspend() const noexcept
+        void setContinuation(std::coroutine_handle<> handle)
         {
-            return {};
+            continuation_ = handle;
+        }
+
+        auto final_suspend() const noexcept
+        {
+            // Can't simply use suspend_never because we need symmetric transfer
+            struct awaiter final
+            {
+                bool await_ready() const noexcept
+                {
+                    return true;
+                }
+
+                auto await_suspend(
+                    std::coroutine_handle<promise_type> coro) const noexcept
+                {
+                    return coro.promise().continuation_;
+                }
+
+                void await_resume() const noexcept
+                {
+                }
+            };
+
+            return awaiter{};
         }
     };
 
+    bool await_ready() const noexcept
+    {
+        return coro_.done();
+    }
+
+    void await_resume() const noexcept
+    {
+    }
+
+    auto await_suspend(std::coroutine_handle<> coroutine) noexcept
+    {
+        coro_.promise().setContinuation(coroutine);
+        return coro_;
+    }
+
     handle_type coro_;
 };
 

lib/tests/unittests/CoroutineTest.cc

@@ -31,7 +31,7 @@ struct StructAwaiter : public CallbackAwaiter<std::shared_ptr<SomeStruct>>
 
 }  // namespace drogon::internal
 
-// Workaround limitation of macros
+// Workarround limitation of macros
 template <typename T>
 using is_int = std::is_same<T, int>;
 template <typename T>
@@ -69,7 +69,7 @@ DROGON_TEST(CroutineBasics)
     }());
     CHECK(n == 1);
 
-    // Testing that exceptions can propagate through coroutines
+    // Testing that exceptions can propergate through coroutines
     auto throw_in_task = [TEST_CTX]() -> Task<> {
         auto f = []() -> Task<> { throw std::runtime_error("test error"); };
 
@@ -77,7 +77,7 @@ DROGON_TEST(CroutineBasics)
     };
     sync_wait(throw_in_task());
 
-    // Test sync_wait propagates exception
+    // Test sync_wait propergrates exception
     auto throws = []() -> Task<> {
         throw std::runtime_error("bla");
         co_return;
@@ -100,7 +100,7 @@ DROGON_TEST(CroutineBasics)
     };
     sync_wait(await_non_copyable());
 
-    // This only works because async_run tries to run the coroutine as soon as
+    // This only works because async_run tries to run the corouine as soon as
     // possible and the coroutine does not wait
     int testVar = 0;
     async_run([&testVar]() -> Task<void> {

nosql_lib/redis/inc/drogon/nosql/RedisClient.h

@@ -164,40 +164,26 @@ class DROGON_EXPORT RedisClient
                       std::string_view command,
                       Args &&...args)
     {
-        return execCommandSync<std::decay_t<decltype(processFunc)>>(
+        std::shared_ptr<std::promise<T>> pro(new std::promise<T>);
-            std::move(processFunc), command, std::forward<Args>(args)...);
+        std::future<T> f = pro->get_future();
-    }
-
-    /**
-     * @brief Execute a redis command synchronously
-     * Return type can be deduced automatically in this version.
-     */
-    template <typename F, typename... Args>
-    std::invoke_result_t<F, const RedisResult &> execCommandSync(
-        F &&processFunc,
-        std::string_view command,
-        Args &&...args)
-    {
-        using Ret = std::invoke_result_t<F, const RedisResult &>;
-        std::promise<Ret> prom;
         execCommandAsync(
-            [&processFunc, &prom](const RedisResult &result) {
+            [process = std::move(processFunc), pro](const RedisResult &result) {
                 try
                 {
-                    prom.set_value(processFunc(result));
+                    pro->set_value(process(result));
                 }
                 catch (...)
                 {
-                    prom.set_exception(std::current_exception());
+                    pro->set_exception(std::current_exception());
                 }
             },
-            [&prom](const RedisException &err) {
+            [pro](const RedisException &err) {
-                prom.set_exception(std::make_exception_ptr(err));
+                pro->set_exception(std::make_exception_ptr(err));
             },
             command,
             std::forward<Args>(args)...);
 
-        return prom.get_future().get();
+        return f.get();
     }
 
     /**

nosql_lib/redis/tests/redis_test.cc

@@ -168,14 +168,11 @@ DROGON_TEST(RedisTest)
         SUCCESS();
     }
 
-    // 12. Test omit template parameter
     try
     {
-        auto i = redisClient->execCommandSync(
+        redisClient->execCommandSync<int>([](const RedisResult &) { return 1; },
-            [](const RedisResult &r) { return r.asInteger(); },
+                                          "del %s",
-            "del %s",
+                                          "sync_key");
-            "sync_key");
-        MANDATE(i == 1);
     }
     catch (const RedisException &err)
     {

trantor

@@ -1 +1 @@
-Subproject commit 528406f0567e6ac48356eeb2b4b7b9ba06e8593e
+Subproject commit 2b6c9d62e6414fe90b456db829723814a534545e