support lazy callback (#647)

include/ylt/coro_io/coro_io.hpp

@@ -42,6 +42,10 @@
 
 namespace coro_io {
 
+template <typename T>
+constexpr inline bool is_lazy_v =
+    util::is_specialization_v<std::remove_cvref_t<T>, async_simple::coro::Lazy>;
+
 template <typename Arg, typename Derived>
 class callback_awaitor_base {
  private:
@@ -395,9 +399,64 @@ async_simple::coro::Lazy<std::pair<
   });
 }
 
+template <typename T>
+inline decltype(auto) select_impl(T &pair) {
+  using Func = std::tuple_element_t<1, std::remove_cvref_t<T>>;
+  using ValueType =
+      typename std::tuple_element_t<0, std::remove_cvref_t<T>>::ValueType;
+  using return_type = std::invoke_result_t<Func, async_simple::Try<ValueType>>;
+
+  auto &callback = std::get<1>(pair);
+  if constexpr (coro_io::is_lazy_v<return_type>) {
+    auto executor = std::get<0>(pair).getExecutor();
+    return std::make_pair(
+        std::move(std::get<0>(pair)),
+        [executor, callback = std::move(callback)](auto &&val) {
+          if (executor) {
+            callback(std::move(val)).via(executor).start([](auto &&) {
+            });
+          }
+          else {
+            callback(std::move(val)).start([](auto &&) {
+            });
+          }
+        });
+  }
+  else {
+    return pair;
+  }
+}
+
 template <typename... T>
-auto select(T &&...args) {
-  return async_simple::coro::collectAny(std::forward<T>(args)...);
+inline auto select(T &&...args) {
+  return async_simple::coro::collectAny(select_impl(args)...);
+}
+
+template <typename T, typename Callback>
+inline auto select(std::vector<T> vec, Callback callback) {
+  if constexpr (coro_io::is_lazy_v<Callback>) {
+    std::vector<async_simple::Executor *> executors;
+    for (auto &lazy : vec) {
+      executors.push_back(lazy.getExecutor());
+    }
+
+    return async_simple::coro::collectAny(
+        std::move(vec),
+        [executors, callback = std::move(callback)](size_t index, auto &&val) {
+          auto executor = executors[index];
+          if (executor) {
+            callback(index, std::move(val)).via(executor).start([](auto &&) {
+            });
+          }
+          else {
+            callback(index, std::move(val)).start([](auto &&) {
+            });
+          }
+        });
+  }
+  else {
+    return async_simple::coro::collectAny(std::move(vec), std::move(callback));
+  }
 }
 
 template <typename Socket, typename AsioBuffer>

include/ylt/thirdparty/async_simple/coro/Collect.h

@@ -152,7 +152,7 @@ struct CollectAnyAwaiter {
                     auto count = e->downCount();
                     if (count == size + 1) {
                         r->_idx = i;
-                        (*callback)(i, std::move(result));
+                        (void)(*callback)(i, std::move(result));
                         c.resume();
                     }
                 });
@@ -222,7 +222,7 @@ struct CollectAnyVariadicPairAwaiter {
                                 callback](auto&& res) mutable {
                         auto count = event->downCount();
                         if (count == std::tuple_size<InputType>() + 1) {
-                            callback(std::move(res));
+                            (void)callback(std::move(res));
                             *result = I;
                             continuation.resume();
                         }

src/coro_io/tests/test_coro_channel.cpp

@@ -111,7 +111,43 @@ async_simple::coro::Lazy<void> test_select_channel() {
   }
 }
 
+void callback_lazy() {
+  using namespace async_simple::coro;
+  auto test0 = []() mutable -> Lazy<int> {
+    co_return 41;
+  };
+
+  auto test1 = []() mutable -> Lazy<int> {
+    co_return 42;
+  };
+
+  auto collectAnyLazy = [](auto&&... args) mutable -> Lazy<size_t> {
+    co_return co_await collectAny(std::move(args)...);
+  };
+
+  syncAwait(
+      collectAnyLazy(std::pair{test1(), [&](auto&& val) mutable -> Lazy<void> {
+                                 CHECK(val.value() == 42);
+                                 int r = co_await test0();
+                                 int result = r + val.value();
+                                 CHECK(result == 83);
+                               }}));
+
+  std::vector<Lazy<int>> input;
+  input.push_back(test1());
+
+  auto index = syncAwait(collectAnyLazy(
+      std::move(input), [&test0](size_t index, auto val) mutable -> Lazy<void> {
+        CHECK(val.value() == 42);
+        int r = co_await test0();
+        int result = r + val.value();
+        CHECK(result == 83);
+      }));
+  CHECK(index == 0);
+}
+
 TEST_CASE("test channel send recieve, test select channel and coroutine") {
   async_simple::coro::syncAwait(test_coro_channel());
   async_simple::coro::syncAwait(test_select_channel());
+  callback_lazy();
 }