Accept a bare outgoing_connection block and log the bound enforcement

esphome/components/api/__init__.py

@@ -314,7 +314,7 @@ def _validate_outgoing_connection(config: ConfigType) -> ConfigType:
     return config
 
 
-OUTGOING_CONNECTION_SCHEMA = cv.Schema(
+_OUTGOING_CONNECTION_SCHEMA = cv.Schema(
     {
         cv.Optional(CONF_HOST): cv.ipaddress,
         cv.Optional(CONF_PORT, default=6054): cv.port,
@@ -323,6 +323,14 @@ OUTGOING_CONNECTION_SCHEMA = cv.Schema(
 )
 
 
+def _outgoing_connection_schema(config: ConfigType | None) -> ConfigType:
+    # A bare `outgoing_connection:` block is valid; without a host the device
+    # dials the remembered last dial-back client
+    if config is None:
+        config = {}
+    return _OUTGOING_CONNECTION_SCHEMA(config)
+
+
 CONFIG_SCHEMA = cv.All(
     cv.Schema(
         {
@@ -347,7 +355,7 @@ CONFIG_SCHEMA = cv.All(
             ): ACTIONS_SCHEMA,
             cv.Exclusive(CONF_ACTIONS, group_of_exclusion=CONF_ACTIONS): ACTIONS_SCHEMA,
             cv.Optional(CONF_ENCRYPTION): encryption_schema,
-            cv.Optional(CONF_OUTGOING_CONNECTION): OUTGOING_CONNECTION_SCHEMA,
+            cv.Optional(CONF_OUTGOING_CONNECTION): _outgoing_connection_schema,
             cv.Optional(CONF_BATCH_DELAY, default="100ms"): cv.All(
                 cv.positive_time_period_milliseconds,
                 cv.Range(max=cv.TimePeriod(milliseconds=65535)),

esphome/components/api/api_server.cpp

@@ -285,6 +285,7 @@ void __attribute__((flatten)) APIServer::accept_new_connections_() {
 bool APIServer::add_client_(APIConnection *conn) {
   if (this->at_client_limit_()) {
     // Callers check first; enforce the array bound where the write happens
+    ESP_LOGW(TAG, "Max connections (%d), dropping client", MAX_API_CONNECTIONS);
     delete conn;
     return false;
   }

tests/component_tests/api/test_outgoing_connection.py

@@ -51,6 +51,18 @@ def test_outgoing_connection_defaults(
     assert outgoing["delay"].total_milliseconds == 60000
 
 
+def test_outgoing_connection_bare_block(
+    set_core_config: SetCoreConfigCallable,
+) -> None:
+    """A bare outgoing_connection: block is valid; the device dials the
+    remembered last dial-back client."""
+    set_core_config(PlatformFramework.ESP32_IDF, platform_data=ESP32_PLATFORM_DATA)
+    config = CONFIG_SCHEMA(_api_config(None))
+    outgoing = config["outgoing_connection"]
+    assert "host" not in outgoing
+    assert outgoing["port"] == 6054
+
+
 def test_outgoing_connection_requires_encryption(
     set_core_config: SetCoreConfigCallable,
 ) -> None: