Added support for forwarding exceptions via Future.

source/mijin/async/coroutine.hpp

@@ -5,10 +5,6 @@
 #define MIJIN_ASYNC_COROUTINE_HPP_INCLUDED 1
 
 
-#if !defined(MIJIN_COROUTINE_ENABLE_DEBUG_INFO)
-#   define MIJIN_COROUTINE_ENABLE_DEBUG_INFO 0 // Capture stack each time a coroutine is started. Warning, expensive! // TODO: maybe implement a lighter version only storing the return address?
-#endif
-
 #include <any>
 #include <chrono>
 #include <coroutine>
@@ -27,6 +23,15 @@
 #include "../util/misc.hpp"
 #include "../util/scope_guard.hpp"
 #include "../util/traits.hpp"
+
+#if !defined(MIJIN_COROUTINE_ENABLE_DEBUG_INFO)
+#   define MIJIN_COROUTINE_ENABLE_DEBUG_INFO 0 // Capture stack each time a coroutine is started. Warning, expensive! // TODO: maybe implement a lighter version only storing the return address?
+#endif
+
+#if !defined(MIJIN_COROUTINE_ENABLE_EXCEPTIONS)
+#   define MIJIN_COROUTINE_ENABLE_EXCEPTIONS 0
+#endif
+
 #if MIJIN_COROUTINE_ENABLE_DEBUG_INFO
 #include "../debug/stacktrace.hpp"
 #endif
@@ -186,10 +191,16 @@ struct TaskReturn<void, TPromise>
 };
 }
 
-template<typename TValue>
+template<typename TValue, template<typename> typename TAllocator = MIJIN_DEFAULT_ALLOCATOR>
+using TaskFuture = Future<TValue, TAllocator, MIJIN_COROUTINE_ENABLE_EXCEPTIONS>;
+
+template<typename TValue, template<typename> typename TAllocator = MIJIN_DEFAULT_ALLOCATOR>
+using TaskFuturePtr = FuturePtr<TValue, TAllocator, MIJIN_COROUTINE_ENABLE_EXCEPTIONS>;
+
+template<typename TValue, template<typename> typename TAllocator>
 struct TaskAwaitableFuture
 {
-    FuturePtr<TValue> future;
+    TaskFuturePtr<TValue, TAllocator> future;
 
     [[nodiscard]] constexpr bool await_ready() const MIJIN_NOEXCEPT { return future->ready(); }
     constexpr void await_suspend(std::coroutine_handle<>) const MIJIN_NOEXCEPT {}
@@ -329,12 +340,12 @@ struct TaskPromise : impl::TaskReturn<typename TTraits::result_t, TaskPromise<TT
 
     // constexpr void unhandled_exception() MIJIN_NOEXCEPT {}
 
-    template<typename TValue>
+    template<typename TValue, template<typename> typename TAllocator>
-    auto await_transform(FuturePtr<TValue> future, std::source_location sourceLoc = std::source_location::current()) MIJIN_NOEXCEPT
+    auto await_transform(TaskFuturePtr<TValue, TAllocator> future, std::source_location sourceLoc = std::source_location::current()) MIJIN_NOEXCEPT
     {
         MIJIN_ASSERT(loop_ != nullptr, "Cannot await future outside of a loop!");
         sharedState_->sourceLoc = std::move(sourceLoc);
-        TaskAwaitableFuture<TValue> awaitable{future};
+        TaskAwaitableFuture<TValue, TAllocator> awaitable{future};
         if (!awaitable.await_ready())
         {
             state_.status = TaskStatus::WAITING;
@@ -635,10 +646,10 @@ public:
     void setUncaughtExceptionHandler(exception_handler_t handler) MIJIN_NOEXCEPT { uncaughtExceptionHandler_ = std::move(handler); }
 
     template<typename TResult>
-    FuturePtr<TResult> addTaskImpl(TaskBase<TResult, TAllocator> task, TaskHandle* outHandle) MIJIN_NOEXCEPT;
+    TaskFuturePtr<TResult, TAllocator> addTaskImpl(TaskBase<TResult, TAllocator> task, TaskHandle* outHandle) MIJIN_NOEXCEPT;
 
     template<typename TResult>
-    FuturePtr<TResult> addTask(TaskBase<TResult, TAllocator> task, TaskHandle* outHandle = nullptr) MIJIN_NOEXCEPT
+    TaskFuturePtr<TResult, TAllocator> addTask(TaskBase<TResult, TAllocator> task, TaskHandle* outHandle = nullptr) MIJIN_NOEXCEPT
     {
         static_assert(TaskAllocatorTraits<TAllocator>::default_is_valid_v, "Allocator is not valid when default constructed, use makeTask() instead.");
         return addTaskImpl(std::move(task), outHandle);
@@ -664,7 +675,7 @@ protected:
 protected:
     static inline TaskLoop*& currentLoopStorage() MIJIN_NOEXCEPT;
     template<typename TResult>
-    static inline void setFutureHelper(StoredTask& storedTask) MIJIN_NOEXCEPT;
+    static inline void setFutureHelper(StoredTask& storedTask) MIJIN_NOEXCEPT_IF(!MIJIN_COROUTINE_ENABLE_EXCEPTIONS);
 };
 
 template<typename TResult = void>
@@ -811,12 +822,12 @@ TaskBase<TResult, TAllocator>::~TaskBase() MIJIN_NOEXCEPT
 
 template<template<typename> typename TAllocator>
 template<typename TResult>
-FuturePtr<TResult> TaskLoop<TAllocator>::addTaskImpl(TaskBase<TResult, TAllocator> task, TaskHandle* outHandle) MIJIN_NOEXCEPT
+TaskFuturePtr<TResult, TAllocator> TaskLoop<TAllocator>::addTaskImpl(TaskBase<TResult, TAllocator> task, TaskHandle* outHandle) MIJIN_NOEXCEPT
 {
     MIJIN_ASSERT(!task.getLoop(), "Attempting to add task that already has a loop!");
     task.setLoop(this);
 
-    FuturePtr<TResult> future = std::allocate_shared<Future<TResult>>(TAllocator<Future<TResult>>(allocator_), allocator_);
+    TaskFuturePtr<TResult, TAllocator> future = std::allocate_shared<TaskFuture<TResult, TAllocator>>(TAllocator<Future<TResult, TAllocator>>(allocator_), allocator_);
     auto setFuture = &setFutureHelper<TResult>;
 
     if (outHandle != nullptr)
@@ -855,7 +866,7 @@ TaskStatus TaskLoop<TAllocator>::tickTask(StoredTask& task)
     while (status == TaskStatus::RUNNING);
     impl::gCurrentTaskState = nullptr;
 
-#if MIJIN_COROUTINE_ENABLE_EXCEPTION_HANDLING
+#if MIJIN_COROUTINE_ENABLE_EXCEPTION_HANDLING && !MIJIN_COROUTINE_ENABLE_EXCEPTIONS
     if (task.task && task.task->exception())
     {
         try
@@ -882,9 +893,24 @@ TaskStatus TaskLoop<TAllocator>::tickTask(StoredTask& task)
     }
 #endif // MIJIN_COROUTINE_ENABLE_EXCEPTION_HANDLING
     if (status == TaskStatus::YIELDED || status == TaskStatus::FINISHED)
+    {
+        try
         {
             task.setFuture(task);
         }
+        catch(TaskCancelled&) {}
+        catch(...)
+        {
+            if (uncaughtExceptionHandler_)
+            {
+                uncaughtExceptionHandler_(std::current_exception());
+            }
+            else
+            {
+                throw;
+            }
+        }
+    }
     return status;
 }
 
@@ -910,10 +936,22 @@ template<template<typename> typename TAllocator>
 
 template<template<typename> typename TAllocator>
 template<typename TResult>
-/* static */ inline void TaskLoop<TAllocator>::setFutureHelper(StoredTask& storedTask) MIJIN_NOEXCEPT
+/* static */ inline void TaskLoop<TAllocator>::setFutureHelper(StoredTask& storedTask) MIJIN_NOEXCEPT_IF(!MIJIN_COROUTINE_ENABLE_EXCEPTIONS)
 {
     TaskBase<TResult, TAllocator>& task = *static_cast<TaskBase<TResult, TAllocator>*>(storedTask.task->raw());
-    auto future = std::any_cast<FuturePtr<TResult>>(storedTask.resultData);
+    const auto& future = std::any_cast<TaskFuturePtr<TResult, TAllocator>&>(storedTask.resultData);
+#if MIJIN_COROUTINE_ENABLE_EXCEPTIONS
+    if (task.state().exception)
+    {
+        if (future.use_count() < 2)
+        {
+            // future has been discarded, but someone must handle the exception
+            std::rethrow_exception(task.state().exception);
+        }
+        future->setException(task.state().exception);
+        return;
+    }
+#endif
 
     if constexpr (!std::is_same_v<TResult, void>)
     {
@@ -1249,14 +1287,14 @@ inline TaskAwaitableSuspend c_suspend() {
     return TaskAwaitableSuspend();
 }
 
-template<template<typename...> typename TCollection, typename TType, typename... TTemplateArgs>
+template<template<typename...> typename TCollection, FutureType TFuture, typename... TTemplateArgs>
-Task<> c_allDone(const TCollection<FuturePtr<TType>, TTemplateArgs...>& futures)
+Task<> c_allDone(const TCollection<TFuture, TTemplateArgs...>& futures)
 {
     bool allDone = true;
     do
     {
         allDone = true;
-        for (const FuturePtr<TType>& future : futures)
+        for (const TFuture& future : futures)
         {
             if (future && !future->ready()) {
                 allDone = false;

source/mijin/async/future.hpp

@@ -4,6 +4,7 @@
 #if !defined(MIJIN_ASYNC_FUTURE_HPP_INCLUDED)
 #define MIJIN_ASYNC_FUTURE_HPP_INCLUDED 1
 
+#include <exception>
 #include <memory>
 #include <optional>
 #include <tuple>
@@ -27,43 +28,113 @@ namespace mijin
 //
 // public types
 //
-template<typename TValue, template<typename> typename TAllocator = MIJIN_DEFAULT_ALLOCATOR>
+template<typename TValue, template<typename> typename TAllocator = MIJIN_DEFAULT_ALLOCATOR, bool exceptions = false>
 class Future;
 
 // TODO: add support for mutexes and waiting for futures
 namespace impl
 {
-template<typename TValue>
+template<typename TValue, bool exceptions>
 struct FutureStorage
 {
     Optional<TValue> value;
 
+    [[nodiscard]]
+    bool hasValue() const MIJIN_NOEXCEPT
+    {
+        return !value.empty();
+    }
+
     void setValue(TValue value_) MIJIN_NOEXCEPT { value = std::move(value_); }
     [[nodiscard]] TValue& getValue() MIJIN_NOEXCEPT { return value.get(); }
 
 };
 
-// template<typename TValue>
+template<>
-// struct FutureStorage<TValue&>
+struct FutureStorage<void, false>
-// {
+{
-//     Optional<TValue*> value;
+    bool isSet = false;
-//
+
-//     void setValue(TValue& value_) MIJIN_NOEXCEPT { value = &value_; }
+    [[nodiscard]]
-//     [[nodiscard]] TValue& getValue() const MIJIN_NOEXCEPT { return *value.get(); }
+    bool hasValue() const MIJIN_NOEXCEPT
-// };
+    {
+        return isSet;
+    }
+    void setValue() MIJIN_NOEXCEPT
+    {
+        isSet = true;
+    }
+    void getValue() MIJIN_NOEXCEPT {}
+};
+
+#if MIJIN_ENABLE_EXCEPTIONS
+template<typename TValue>
+struct FutureStorage<TValue, true>
+{
+    Optional<TValue> value;
+    std::exception_ptr exception;
+
+    [[nodiscard]]
+    bool hasValue() const MIJIN_NOEXCEPT
+    {
+        if (exception) {
+            return true;
+        }
+        return !value.empty();
+    }
+
+    void setException(std::exception_ptr exc) MIJIN_NOEXCEPT
+    {
+        exception = std::move(exc);
+    }
+    void setValue(TValue value_) MIJIN_NOEXCEPT { value = std::move(value_); }
+    [[nodiscard]] TValue& getValue()
+    {
+        if (exception) {
+            std::rethrow_exception(exception);
+        }
+        return value.get();
+    }
+
+};
 
 template<>
-struct FutureStorage<void>
+struct FutureStorage<void, true>
 {
+    bool isSet = false;
+    std::exception_ptr exception;
+
+    [[nodiscard]]
+    bool hasValue() const MIJIN_NOEXCEPT
+    {
+        if (exception) {
+            return true;
+        }
+        return isSet;
+    }
+    void setException(std::exception_ptr exc) MIJIN_NOEXCEPT
+    {
+        exception = std::move(exc);
+    }
+    void setValue() MIJIN_NOEXCEPT
+    {
+        isSet = true;
+    }
+    void getValue()
+    {
+        if (exception) {
+            std::rethrow_exception(exception);
+        }
+    }
 };
+#endif
 } // namespace impl
 
-template<typename TValue, template<typename> typename TAllocator>
+template<typename TValue, template<typename> typename TAllocator, bool exceptions>
 class Future
 {
 private:
-    [[no_unique_address]] impl::FutureStorage<TValue> value_;
+    impl::FutureStorage<TValue, exceptions> value_;
-    bool isSet_ = false;
 public:
     Future() = default;
     Future(const Future&) = delete;
@@ -80,10 +151,12 @@ public:
     constexpr bool operator!() const MIJIN_NOEXCEPT { return !ready(); }
 public: // access
     [[nodiscard]]
-    constexpr decltype(auto) get() MIJIN_NOEXCEPT
+    constexpr decltype(auto) get() MIJIN_NOEXCEPT_IF(!exceptions)
     {
-        MIJIN_ASSERT(isSet_, "Attempting to get from future that is not ready.");
+        MIJIN_ASSERT(ready(), "Attempting to get from future that is not ready.");
-        if constexpr(std::is_same_v<TValue, void>) {
+        if constexpr(std::is_same_v<TValue, void>)
+        {
+            value_.getValue(); // in case of exceptions
             return;
         }
         else {
@@ -91,10 +164,12 @@ public: // access
         }
     }
     [[nodiscard]]
-    constexpr decltype(auto) get() const MIJIN_NOEXCEPT
+    constexpr decltype(auto) get() const MIJIN_NOEXCEPT_IF(!exceptions)
     {
-        MIJIN_ASSERT(isSet_, "Attempting to get from future that is not ready.");
+        MIJIN_ASSERT(ready(), "Attempting to get from future that is not ready.");
-        if constexpr(std::is_same_v<TValue, void>) {
+        if constexpr(std::is_same_v<TValue, void>)
+        {
+            value_.getValue(); // in case of exceptions
             return;
         }
         else {
@@ -104,22 +179,22 @@ public: // access
     [[nodiscard]]
     constexpr bool ready() const MIJIN_NOEXCEPT
     {
-        return isSet_;
+        return value_.hasValue();
     }
 public: // modification
     template<typename TArg> requires (!std::is_same_v<TValue, void>)
     constexpr void set(TArg&& value) MIJIN_NOEXCEPT
     {
-        MIJIN_ASSERT(!isSet_, "Trying to set a future twice!");
+        MIJIN_ASSERT(!ready(), "Trying to set a future twice!");
         value_.setValue(std::move(value));
-        isSet_ = true;
         sigSet.emit();
     }
     constexpr void set() MIJIN_NOEXCEPT requires (std::is_same_v<TValue, void>)
     {
-        MIJIN_ASSERT(!isSet_, "Trying to set a future twice!");
+        MIJIN_ASSERT(!ready(), "Trying to set a future twice!");
-        isSet_ = true;
+        if constexpr (std::is_same_v<TValue, void>)
-        if constexpr (std::is_same_v<TValue, void>) {
+        {
+            value_.setValue();
             sigSet.emit();
         }
         else {
@@ -127,12 +202,38 @@ public: // modification
             MIJIN_ERROR("Attempting to call set(void) on future with value.");
         }
     }
+    constexpr void setException(std::exception_ptr exception) requires (exceptions)
+    {
+        MIJIN_ASSERT(!ready(), "Trying to set a future twice!");
+        if constexpr (exceptions)
+        {
+            value_.setException(std::move(exception));
+        }
+    }
 public: // signals
     BaseSignal<TAllocator> sigSet;
 };
 
+template<typename TValue = void, template<typename> typename TAllocator = MIJIN_DEFAULT_ALLOCATOR, bool exceptions = false>
+using FuturePtr = std::shared_ptr<Future<TValue, TAllocator, exceptions>>;
+
 template<typename TValue = void, template<typename> typename TAllocator = MIJIN_DEFAULT_ALLOCATOR>
-using FuturePtr = std::shared_ptr<Future<TValue, TAllocator>>;
+using ExceptFuture = Future<TValue, TAllocator, true>;
+
+template<typename TValue = void, template<typename> typename TAllocator = MIJIN_DEFAULT_ALLOCATOR>
+using ExceptFuturePtr = std::shared_ptr<Future<TValue, TAllocator, true>>;
+
+template<typename T>
+struct is_future : std::false_type {};
+
+template<typename TValue, template<typename> typename TAllocator, bool exceptions>
+struct is_future<Future<TValue, TAllocator, exceptions>> : std::true_type {};
+
+template<typename T>
+inline constexpr bool is_future_t = is_future<T>::value;
+
+template<typename T>
+concept FutureType = is_future<T>::value;
 
 //
 // public functions