Don't auto-throw non-viral callee exceptions before callerLambda

include/spinscale/co/nonViralCompletion.h

@@ -0,0 +1,40 @@
+#ifndef NON_VIRAL_COMPLETION_H
+#define NON_VIRAL_COMPLETION_H
+
+#include <exception>
+#include <utility>
+
+namespace sscl::co {
+
+class NonViralCompletion
+{
+public:
+	explicit NonViralCompletion(std::exception_ptr &exceptionPtr)
+	: exceptionPtr(exceptionPtr)
+	{}
+
+	bool hasException() const noexcept
+	{
+		return exceptionPtr != nullptr;
+	}
+
+	void checkAndRethrowException() const
+	{
+		if (exceptionPtr)
+		{
+			std::rethrow_exception(exceptionPtr);
+		}
+	}
+
+	std::exception_ptr releaseException() noexcept
+	{
+		return std::exchange(exceptionPtr, nullptr);
+	}
+
+private:
+	std::exception_ptr &exceptionPtr;
+};
+
+} // namespace sscl::co
+
+#endif // NON_VIRAL_COMPLETION_H