fix(mqtt): count connect failures from a flag set before the attempt

The Starting-state gate raced the event task: client_state becomes Starting
only after connect()/reconnect() returns, so a fast failure could deliver
DISCONNECTED first and go uncounted, while a deliberate stop of an attempt in
flight was counted as a failure. A per-slot flag is now raised before the call
and cleared by onConnect, a failed start, or stopSlotClient().

Also stops zero-valued connect_failures/slots_breaker from creating an empty
stats object.

src/helpers/MQTTPayloadBuilder.cpp

@@ -65,7 +65,7 @@ int MQTTPayloadBuilder::buildStatusMessage(
 
   const bool has_conn_health = conn_health.slots_up >= 0 || conn_health.slots_total >= 0 ||
       conn_health.worst_outage_secs >= 0 || conn_health.heap_largest >= 0 ||
-      conn_health.connect_failures >= 0 || conn_health.slots_breaker >= 0;
+      conn_health.connect_failures > 0 || conn_health.slots_breaker > 0;
 
   if (battery_mv >= 0 || uptime_secs >= 0 || errors >= 0 || queue_len >= 0 ||
       noise_floor > -999 || tx_air_secs >= 0 || rx_air_secs >= 0 || recv_errors >= 0 ||

src/helpers/bridges/MQTTBridge.cpp

@@ -772,6 +772,7 @@ MQTTBridge::MQTTBridge(NodePrefs *prefs, MQTTPrefs *obs, mesh::PacketManager *mg
     _slot_reconfigure_pending[i] = false;
     _slot_force_jwt_mint[i] = false;
     _status_publish_pending[i] = false;
+    _slot_attempt_pending[i] = false;
   }
 
   // Reset CLI-requested forced NTP sync handshake (bridge object is reused across restarts)
@@ -1730,6 +1731,7 @@ bool MQTTBridge::ensureSlotClient(int index) {
       return;
     }
     MQTT_DEBUG_PRINTLN("MQTT%d connected", index + 1);
+    _slot_attempt_pending[index] = false;
     _slots[index].client_state = ClientState::Connected;
     _slots[index].connected = true;
     _slot_force_jwt_mint[index] = false;
@@ -1763,9 +1765,10 @@ bool MQTTBridge::ensureSlotClient(int index) {
   });
   slot.client->onDisconnect([this, index](bool sessionPresent) {
     MQTT_DEBUG_PRINTLN("MQTT%d disconnected", index + 1);
-    // An event while an attempt is in flight ended one that never reached onConnect.
-    // Stopped/quarantined late events and soft-disconnects are not Starting.
-    if (mqttClientStateHasAttemptInFlight(_slots[index].client_state)) {
+    // Ended an attempt that never reached onConnect. A deliberate stop clears the flag
+    // first, so cancelling an attempt is not counted as a failure.
+    if (_slot_attempt_pending[index]) {
+      _slot_attempt_pending[index] = false;
       _slots[index].connect_failures++;
     }
     // Only a live client's disconnect is news. One arriving for a client we
@@ -2411,6 +2414,7 @@ void MQTTBridge::closeLiveClientForLinkTransition(int index) {
 // the rest of the boot.
 void MQTTBridge::stopSlotClient(int index) {
   MQTTSlot& slot = _slots[index];
+  _slot_attempt_pending[index] = false;
   const esp_err_t r = slot.client->disconnect();
 
   // What the SDK's results actually mean here (mqtt_client.h documents
@@ -2505,6 +2509,7 @@ esp_err_t MQTTBridge::reconnectSlotClient(int index) {
   }
 
   esp_err_t r;
+  _slot_attempt_pending[index] = true;
   if (!slot.client->isStarted()) {
     MQTT_DEBUG_PRINTLN("MQTT%d start (client was stopped)", index + 1);
     r = slot.client->connect();
@@ -2517,6 +2522,8 @@ esp_err_t MQTTBridge::reconnectSlotClient(int index) {
     // The attempt carries whatever credential is configured right now, so this
     // is the point at which a freshly minted token becomes the one in use.
     slot.applied_token_expires_at = slot.token_expires_at;
+  } else {
+    _slot_attempt_pending[index] = false;
   }
   return r;
 }

src/helpers/bridges/MQTTBridge.h

@@ -286,6 +286,11 @@ private:
   // _slot_reconfigure_pending; a single-byte volatile store/load is atomic.
   volatile bool _status_publish_pending[RUNTIME_MQTT_SLOTS];
 
+  // Set by the bridge task before connect()/reconnect(), so a failure the event task
+  // delivers before that call returns is still seen; cleared by the attempt's outcome
+  // or a deliberate stop. A disconnect that finds it set is a connect failure.
+  volatile bool _slot_attempt_pending[RUNTIME_MQTT_SLOTS];
+
   // CLI-requested forced NTP sync, marshalled onto the MQTT task (Core 0).
   // All NTP I/O must run on Core 0; the CLI thread
   // (Core 1) sets _ntp_force_requested and blocks in requestForcedNtpSync()

test/test_mqtt_payload_builder/test_mqtt_payload_builder.cpp

@@ -158,6 +158,23 @@ TEST(MQTTPayloadBuilder, StatusReportsConnectFailuresAndBreakerOnlyWhenNonZero)
   EXPECT_FALSE(healthy_stats["mqtt_slots_breaker"].is<JsonVariant>());
 }
 
+// Zero counters with nothing else supplied must not create an empty stats object.
+TEST(MQTTPayloadBuilder, StatusOmitsStatsWhenOnlyZeroCountersSupplied) {
+  JsonDocument scratch;
+  char buffer[768];
+  MQTTConnHealth health;
+  health.connect_failures = 0;
+  health.slots_breaker = 0;
+
+  ASSERT_GT(MQTTPayloadBuilder::buildStatusMessage(
+      scratch, "node", "id", "model", "firmware", "radio", "client", "online",
+      kTimestamp, buffer, sizeof(buffer), -1, -1, -1, -1, -999,
+      -1, -1, -1, -1, -1, -1, nullptr, health), 0);
+  JsonDocument parsed;
+  ASSERT_FALSE(deserializeJson(parsed, buffer));
+  EXPECT_FALSE(parsed["stats"].is<JsonVariant>());
+}
+
 // The outage key doubles as the "something is down" flag, so its absence has to be
 // meaningful: a fully healthy board must not emit it.
 TEST(MQTTPayloadBuilder, StatusOmitsOutageKeyWhenEverySlotIsUp) {