Add Task<T>::result() for accessing completed task values without co_await

README.md

@@ -629,6 +629,7 @@ See [rclcpp_async/test/benchmark/README.md](rclcpp_async/test/benchmark/README.m
 |---|---|---|
 | `operator bool()` | `bool` | `true` if the task holds a valid coroutine (not moved-from) |
 | `done()` | `bool` | `true` if the coroutine has completed (`false` for null tasks) |
+| `result()` | `T&` | Get the result of a completed `Task<T>` (rethrows if exception) |
 | `cancel()` | `void` | Request cancellation via `CancelledException` |
 
 ```cpp
@@ -638,7 +639,7 @@ if (task) {       // true -- valid coroutine
   // ...
 }
 if (task.done()) {
-  // coroutine has finished
+  auto & value = task.result();  // access the result without co_await
 }
 ```
 

rclcpp_async/include/rclcpp_async/task.hpp

@@ -116,6 +116,14 @@ struct Task
     return std::move(*handle.promise().value);
   }
 
+  T & result()
+  {
+    if (handle.promise().exception) {
+      std::rethrow_exception(handle.promise().exception);
+    }
+    return *handle.promise().value;
+  }
+
   void cancel() { handle.promise().stop_source.request_stop(); }
 
   explicit operator bool() const noexcept { return handle != nullptr; }

rclcpp_async/test/test_task.cpp

@@ -271,6 +271,31 @@ TEST(TaskT, OperatorBoolAndDone)
   EXPECT_TRUE(task2.done());
 }
 
+TEST(TaskT, ResultReturnsValue)
+{
+  auto task = returns_42();
+  task.handle.resume();
+  ASSERT_TRUE(task.done());
+  EXPECT_EQ(task.result(), 42);
+}
+
+TEST(TaskT, ResultReturnsReference)
+{
+  auto task = returns_42();
+  task.handle.resume();
+  ASSERT_TRUE(task.done());
+  task.result() = 99;
+  EXPECT_EQ(task.result(), 99);
+}
+
+TEST(TaskT, ResultRethrowsException)
+{
+  auto task = throws_runtime_error();
+  task.handle.resume();
+  ASSERT_TRUE(task.done());
+  EXPECT_THROW(task.result(), std::runtime_error);
+}
+
 TEST(TaskVoid, OperatorBoolAndDone)
 {
   auto task = does_nothing();