From 6a802b2359deb9e94a4b404928faace49263dc59 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Piotr=20W=C3=B3jcik?=
 <3044353+pwojcikdev@users.noreply.github.com>
Date: Tue, 2 Jul 2024 09:48:12 +0200
Subject: [PATCH] Do not wait for cancellation signal (#4664)

* Do not wait for cancelation signal

* Test

* Explicit constructor
---
 nano/core_test/async.cpp | 22 +++++++++++++++++++++-
 nano/lib/async.hpp       | 18 ++++++++----------
 2 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/nano/core_test/async.cpp b/nano/core_test/async.cpp
index e0be0a732..cef6e082f 100644
--- a/nano/core_test/async.cpp
+++ b/nano/core_test/async.cpp
@@ -56,10 +56,30 @@ TEST (async, cancellation)
 
 	cancellation.emit ();
 
-	ASSERT_EQ (fut.wait_for (500ms), std::future_status::ready);
+	ASSERT_EQ (fut.wait_for (1s), std::future_status::ready);
 	ASSERT_NO_THROW (fut.get ());
 }
 
+// Test that cancellation signal behaves well when the cancellation is emitted after the task has completed
+TEST (async, cancellation_lifetime)
+{
+	test_context ctx;
+
+	nano::async::cancellation cancellation{ ctx.strand };
+	{
+		auto fut = asio::co_spawn (
+		ctx.strand,
+		[&] () -> asio::awaitable<void> {
+			co_await nano::async::sleep_for (100ms);
+		},
+		asio::bind_cancellation_slot (cancellation.slot (), asio::use_future));
+		ASSERT_EQ (fut.wait_for (1s), std::future_status::ready);
+		fut.get ();
+	}
+	auto cancel_fut = cancellation.emit ();
+	ASSERT_EQ (cancel_fut.wait_for (1s), std::future_status::ready);
+}
+
 TEST (async, task)
 {
 	nano::test::system system;
diff --git a/nano/lib/async.hpp b/nano/lib/async.hpp
index b217ba881..818d6bcaf 100644
--- a/nano/lib/async.hpp
+++ b/nano/lib/async.hpp
@@ -30,7 +30,7 @@ class cancellation
 public:
 	explicit cancellation (nano::async::strand & strand) :
 		strand{ strand },
-		signal{ std::make_unique<asio::cancellation_signal> () }
+		signal{ std::make_shared<asio::cancellation_signal> () }
 	{
 	}
 
@@ -49,12 +49,11 @@ public:
 	};
 
 public:
-	void emit (asio::cancellation_type type = asio::cancellation_type::all)
+	auto emit (asio::cancellation_type type = asio::cancellation_type::all)
 	{
-		asio::dispatch (strand, asio::use_future ([this, type] () {
-			signal->emit (type);
-		}))
-		.wait ();
+		return asio::dispatch (strand, asio::use_future ([signal_l = signal, type] () {
+			signal_l->emit (type);
+		}));
 	}
 
 	auto slot ()
@@ -67,9 +66,8 @@ public:
 	nano::async::strand & strand;
 
 private:
-	std::unique_ptr<asio::cancellation_signal> signal; // Wrap the signal in a unique_ptr to enable moving
-
-	bool slotted{ false };
+	std::shared_ptr<asio::cancellation_signal> signal;
+	bool slotted{ false }; // For debugging purposes
 };
 
 /**
@@ -82,7 +80,7 @@ public:
 	// Only thread-like void tasks are supported for now
 	using value_type = void;
 
-	task (nano::async::strand & strand) :
+	explicit task (nano::async::strand & strand) :
 		strand{ strand },
 		cancellation{ strand }
 	{