Add a convenience for single shot connections

Although this is a trivial wrapper around connectReflective it is
useful to have this to make it easy to find and reduce the burden
on the developer.

src/kdbindings/signal.h

@@ -362,6 +362,30 @@ class Signal
         return ConnectionHandle{ m_impl, m_impl->connectReflective(slot) };
     }
 
+    /**
+     * Establishes a single-shot connection between a signal and a slot and when the signal is emitted, the connection will be
+     * disconnected and the slot will be called. Note that the slot will be disconnected before it is called. If the slot
+     * triggers another signal emission of the same signal, the slot will not be called again.
+     *
+     * @param slot A std::function that takes the signal's parameter types.
+     * @return An instance of ConnectionHandle, that can be used to disconnect.
+     *
+     * @warning Connecting functions to a signal that throw an exception when called is currently undefined behavior.
+     * All connected functions should handle their own exceptions.
+     * For backwards-compatibility, the slot function is not required to be noexcept.
+     */
+    KDBINDINGS_WARN_UNUSED ConnectionHandle connectSingleShot(std::function<void(Args...)> const &slot)
+    {
+        ensureImpl();
+
+        auto singleShotSlot = [slot](ConnectionHandle &handle, Args... args) {
+            handle.disconnect();
+            slot(args...);
+        };
+
+        return ConnectionHandle{ m_impl, m_impl->connectReflective(singleShotSlot) };
+    }
+
     /**
      * @brief Establishes a deferred connection between the provided evaluator and slot.
      *

tests/signal/tst_signal.cpp

@@ -270,12 +270,9 @@ TEST_CASE("Signal connections")
         Signal<int> mySignal;
         int val = 5;
 
-        // Connect a reflective slot to the signal
-        auto handle = mySignal.connectReflective([&val](ConnectionHandle &selfHandle, int value) {
+        // Connect a single shot slot to the signal
+        auto handle = mySignal.connectSingleShot([&val](int value) {
             val += value;
-
-            // Disconnect after handling the signal once
-            selfHandle.disconnect();
         });
 
         mySignal.emit(5); // This should trigger the slot and then disconnect it