Fix for a race condition in WiFi connection loop

There seems to be the race between the event RW_EVT_STA_CONNECTED
and an actual valid SSID value returned by BDK. If even a small delay
is injected immediately after the event reception the valid value
becomes available. Without this fix, due to a polling nature of ESPHome
WiFiComponent::check_connecting_finished function may observe the
WiFiSTAConnectStatus::CONNECTED status but with an empty SSID value,
leading to `Incomplete connection.` warning and immediate attempt to
start another connection, while the current one was actually established.

cores/beken-72xx/arduino/libraries/WiFi/WiFiEvents.cpp

@@ -27,6 +27,42 @@ static void wifiEventTask(void *arg) {
 	}
 }
 
+// There is a race condition, when we have an event about a successful
+// connection but no SSID yet returned by BDK. Even a sinlge millisecond
+// delay should prevent this from happening. It's better to waste a bit
+// of time here than to lose a valid connection down the line.
+static String waitForValidSSID(WiFiClass * pWiFi)
+{
+	String result;
+
+	// Read the initial value that might just be available already.
+	result = pWiFi->SSID();
+
+	if (!result.length()) {
+		std::size_t i = 0;
+
+		for (; i < 10; ++i) {
+			// Dealy and query again.
+			delay(1);
+			result = pWiFi->SSID();
+
+			if (result.length()) {
+				LT_DM(WIFI, "Got valid SSID after %u delays", i + 1);
+				break;
+			}
+
+			// It's a good idea to yield.
+			yield();
+		}
+
+		if (!result.length()) {
+			LT_DM(WIFI, "Could not obtain a valid SSID after %u delays", i);
+		}
+	}
+
+	return result;
+}
+
 void wifiEventSendArduino(EventId event) {
 	event = (EventId)(RW_EVT_ARDUINO | event);
 	wifiStatusCallback((rw_evt_type *)&event);
@@ -52,11 +88,6 @@ void wifiEventHandler(rw_evt_type event) {
 
 	LT_DM(WIFI, "BK event %u", event);
 
-	if (event <= RW_EVT_STA_GOT_IP)
-		pDATA->lastStaEvent = event;
-	else
-		pDATA->lastApEvent = event;
-
 	EventId eventId;
 	EventInfo eventInfo;
 	String ssid;
@@ -103,7 +134,7 @@ void wifiEventHandler(rw_evt_type event) {
 
 		case RW_EVT_STA_CONNECTED:
 			eventId								  = ARDUINO_EVENT_WIFI_STA_CONNECTED;
-			ssid								  = pWiFi->SSID();
+			ssid								  = waitForValidSSID(pWiFi);
 			eventInfo.wifi_sta_connected.ssid_len = ssid.length();
 			eventInfo.wifi_sta_connected.channel  = pWiFi->channel();
 			eventInfo.wifi_sta_connected.authmode = pWiFi->getEncryption();
@@ -145,5 +176,13 @@ void wifiEventHandler(rw_evt_type event) {
 			break;
 	}
 
+	// Publish state update only after the event data is retrieved.
+	// This relates to the race condition with RW_EVT_STA_CONNECTED.
+	if (event <= RW_EVT_STA_GOT_IP) {
+		pDATA->lastStaEvent = event;
+	} else {
+		pDATA->lastApEvent = event;
+	}
+
 	pWiFi->postEvent(eventId, eventInfo);
 }