Merge branch 'dev' into peername_no_double_ram

esphome/components/api/api_connection.cpp

@@ -133,8 +133,8 @@ void APIConnection::start() {
     return;
   }
   // Initialize client name with peername (IP address) until Hello message provides actual name
-  const char *peername = this->helper_->get_client_peername();
-  this->helper_->set_client_name(peername, strlen(peername));
+  char peername[socket::SOCKADDR_STR_LEN];
+  this->helper_->set_client_name(this->helper_->get_peername_to(peername), strlen(peername));
 }
 
 APIConnection::~APIConnection() {
@@ -179,8 +179,8 @@ void APIConnection::begin_iterator_(ActiveIterator type) {
 
 void APIConnection::loop() {
   if (this->flags_.next_close) {
-    // requested a disconnect
-    this->helper_->close();
+    // requested a disconnect - don't close socket here, let APIServer::loop() do it
+    // so getpeername() still works for the disconnect trigger
     this->flags_.remove = true;
     return;
   }
@@ -293,7 +293,8 @@ bool APIConnection::send_disconnect_response(const DisconnectRequest &msg) {
   return this->send_message(resp, DisconnectResponse::MESSAGE_TYPE);
 }
 void APIConnection::on_disconnect_response(const DisconnectResponse &value) {
-  this->helper_->close();
+  // Don't close socket here, let APIServer::loop() do it
+  // so getpeername() still works for the disconnect trigger
   this->flags_.remove = true;
 }
 
@@ -1524,8 +1525,11 @@ void APIConnection::complete_authentication_() {
   this->flags_.connection_state = static_cast<uint8_t>(ConnectionState::AUTHENTICATED);
   this->log_client_(ESPHOME_LOG_LEVEL_DEBUG, LOG_STR("connected"));
 #ifdef USE_API_CLIENT_CONNECTED_TRIGGER
-  this->parent_->get_client_connected_trigger()->trigger(std::string(this->helper_->get_client_name()),
-                                                         std::string(this->helper_->get_client_peername()));
+  {
+    char peername[socket::SOCKADDR_STR_LEN];
+    this->parent_->get_client_connected_trigger()->trigger(std::string(this->helper_->get_client_name()),
+                                                           std::string(this->helper_->get_peername_to(peername)));
+  }
 #endif
 #ifdef USE_HOMEASSISTANT_TIME
   if (homeassistant::global_homeassistant_time != nullptr) {
@@ -1544,8 +1548,9 @@ bool APIConnection::send_hello_response(const HelloRequest &msg) {
   this->helper_->set_client_name(msg.client_info.c_str(), msg.client_info.size());
   this->client_api_version_major_ = msg.api_version_major;
   this->client_api_version_minor_ = msg.api_version_minor;
+  char peername[socket::SOCKADDR_STR_LEN];
   ESP_LOGV(TAG, "Hello from client: '%s' | %s | API Version %" PRIu32 ".%" PRIu32, this->helper_->get_client_name(),
-           this->helper_->get_client_peername(), this->client_api_version_major_, this->client_api_version_minor_);
+           this->helper_->get_peername_to(peername), this->client_api_version_major_, this->client_api_version_minor_);
 
   HelloResponse resp;
   resp.api_version_major = 1;
@@ -1862,7 +1867,8 @@ void APIConnection::on_no_setup_connection() {
   this->log_client_(ESPHOME_LOG_LEVEL_DEBUG, LOG_STR("no connection setup"));
 }
 void APIConnection::on_fatal_error() {
-  this->helper_->close();
+  // Don't close socket here - keep it open so getpeername() works for logging
+  // Socket will be closed when client is removed from the list in APIServer::loop()
   this->flags_.remove = true;
 }
 
@@ -2218,12 +2224,14 @@ void APIConnection::process_state_subscriptions_() {
 #endif  // USE_API_HOMEASSISTANT_STATES
 
 void APIConnection::log_client_(int level, const LogString *message) {
+  char peername[socket::SOCKADDR_STR_LEN];
   esp_log_printf_(level, TAG, __LINE__, ESPHOME_LOG_FORMAT("%s (%s): %s"), this->helper_->get_client_name(),
-                  this->helper_->get_client_peername(), LOG_STR_ARG(message));
+                  this->helper_->get_peername_to(peername), LOG_STR_ARG(message));
 }
 
 void APIConnection::log_warning_(const LogString *message, APIError err) {
-  ESP_LOGW(TAG, "%s (%s): %s %s errno=%d", this->helper_->get_client_name(), this->helper_->get_client_peername(),
+  char peername[socket::SOCKADDR_STR_LEN];
+  ESP_LOGW(TAG, "%s (%s): %s %s errno=%d", this->helper_->get_client_name(), this->helper_->get_peername_to(peername),
            LOG_STR_ARG(message), LOG_STR_ARG(api_error_to_logstr(err)), errno);
 }
 

esphome/components/api/api_connection.h

@@ -281,8 +281,10 @@ class APIConnection final : public APIServerConnection {
   bool send_buffer(ProtoWriteBuffer buffer, uint8_t message_type) override;
 
   const char *get_name() const { return this->helper_->get_client_name(); }
-  /// Get peer name (IP address) - cached at connection init time
-  const char *get_peername() const { return this->helper_->get_client_peername(); }
+  /// Get peer name (IP address) into caller-provided buffer, returns buf for convenience
+  const char *get_peername_to(std::span<char, socket::SOCKADDR_STR_LEN> buf) const {
+    return this->helper_->get_peername_to(buf);
+  }
 
  protected:
   // Helper function to handle authentication completion

esphome/components/api/api_frame_helper.cpp

@@ -16,7 +16,12 @@ static const char *const TAG = "api.frame_helper";
 static constexpr size_t API_MAX_LOG_BYTES = 168;
 
 #if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERY_VERBOSE
-#define HELPER_LOG(msg, ...) ESP_LOGVV(TAG, "%s (%s): " msg, this->client_name_, this->client_peername_, ##__VA_ARGS__)
+#define HELPER_LOG(msg, ...) \
+  do { \
+    char peername_buf[socket::SOCKADDR_STR_LEN]; \
+    this->get_peername_to(peername_buf); \
+    ESP_LOGVV(TAG, "%s (%s): " msg, this->client_name_, peername_buf, ##__VA_ARGS__); \
+  } while (0)
 #else
 #define HELPER_LOG(msg, ...) ((void) 0)
 #endif
@@ -240,13 +245,20 @@ APIError APIFrameHelper::try_send_tx_buf_() {
   return APIError::OK;  // All buffers sent successfully
 }
 
+const char *APIFrameHelper::get_peername_to(std::span<char, socket::SOCKADDR_STR_LEN> buf) const {
+  if (this->socket_) {
+    this->socket_->getpeername_to(buf);
+  } else {
+    buf[0] = '\0';
+  }
+  return buf.data();
+}
+
 APIError APIFrameHelper::init_common_() {
   if (state_ != State::INITIALIZE || this->socket_ == nullptr) {
     HELPER_LOG("Bad state for init %d", (int) state_);
     return APIError::BAD_STATE;
   }
-  // Cache peername now while socket is valid - needed for error logging after socket failure
-  this->socket_->getpeername_to(this->client_peername_);
   int err = this->socket_->setblocking(false);
   if (err != 0) {
     state_ = State::FAILED;

esphome/components/api/api_frame_helper.h

@@ -90,8 +90,9 @@ class APIFrameHelper {
 
   // Get client name (null-terminated)
   const char *get_client_name() const { return this->client_name_; }
-  // Get client peername/IP (null-terminated, cached at init time for availability after socket failure)
-  const char *get_client_peername() const { return this->client_peername_; }
+  // Get client peername/IP into caller-provided buffer (fetches on-demand from socket)
+  // Returns pointer to buf for convenience in printf-style calls
+  const char *get_peername_to(std::span<char, socket::SOCKADDR_STR_LEN> buf) const;
   // Set client name from buffer with length (truncates if needed)
   void set_client_name(const char *name, size_t len) {
     size_t copy_len = std::min(len, sizeof(this->client_name_) - 1);
@@ -105,6 +106,8 @@ class APIFrameHelper {
   bool can_write_without_blocking() { return this->state_ == State::DATA && this->tx_buf_count_ == 0; }
   int getpeername(struct sockaddr *addr, socklen_t *addrlen) { return socket_->getpeername(addr, addrlen); }
   APIError close() {
+    if (state_ == State::CLOSED)
+      return APIError::OK;  // Already closed
     state_ = State::CLOSED;
     int err = this->socket_->close();
     if (err == -1)
@@ -231,8 +234,6 @@ class APIFrameHelper {
 
   // Client name buffer - stores name from Hello message or initial peername
   char client_name_[CLIENT_INFO_NAME_MAX_LEN]{};
-  // Cached peername/IP address - captured at init time for availability after socket failure
-  char client_peername_[socket::SOCKADDR_STR_LEN]{};
 
   // Group smaller types together
   uint16_t rx_buf_len_ = 0;

esphome/components/api/api_frame_helper_noise.cpp

@@ -29,7 +29,12 @@ static constexpr size_t PROLOGUE_INIT_LEN = 12;  // strlen("NoiseAPIInit")
 static constexpr size_t API_MAX_LOG_BYTES = 168;
 
 #if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERY_VERBOSE
-#define HELPER_LOG(msg, ...) ESP_LOGVV(TAG, "%s (%s): " msg, this->client_name_, this->client_peername_, ##__VA_ARGS__)
+#define HELPER_LOG(msg, ...) \
+  do { \
+    char peername_buf[socket::SOCKADDR_STR_LEN]; \
+    this->get_peername_to(peername_buf); \
+    ESP_LOGVV(TAG, "%s (%s): " msg, this->client_name_, peername_buf, ##__VA_ARGS__); \
+  } while (0)
 #else
 #define HELPER_LOG(msg, ...) ((void) 0)
 #endif

esphome/components/api/api_frame_helper_plaintext.cpp

@@ -21,7 +21,12 @@ static const char *const TAG = "api.plaintext";
 static constexpr size_t API_MAX_LOG_BYTES = 168;
 
 #if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERY_VERBOSE
-#define HELPER_LOG(msg, ...) ESP_LOGVV(TAG, "%s (%s): " msg, this->client_name_, this->client_peername_, ##__VA_ARGS__)
+#define HELPER_LOG(msg, ...) \
+  do { \
+    char peername_buf[socket::SOCKADDR_STR_LEN]; \
+    this->get_peername_to(peername_buf); \
+    ESP_LOGVV(TAG, "%s (%s): " msg, this->client_name_, peername_buf, ##__VA_ARGS__); \
+  } while (0)
 #else
 #define HELPER_LOG(msg, ...) ((void) 0)
 #endif

esphome/components/api/api_server.cpp

@@ -192,11 +192,15 @@ void APIServer::loop() {
     ESP_LOGV(TAG, "Remove connection %s", client->get_name());
 
 #ifdef USE_API_CLIENT_DISCONNECTED_TRIGGER
-    // Save client info before removal for the trigger
+    // Save client info before closing socket and removal for the trigger
+    char peername_buf[socket::SOCKADDR_STR_LEN];
     std::string client_name(client->get_name());
-    std::string client_peername(client->get_peername());
+    std::string client_peername(client->get_peername_to(peername_buf));
 #endif
 
+    // Close socket now (was deferred from on_fatal_error to allow getpeername)
+    client->helper_->close();
+
     // Swap with the last element and pop (avoids expensive vector shifts)
     if (client_index < this->clients_.size() - 1) {
       std::swap(this->clients_[client_index], this->clients_.back());

esphome/components/time/real_time_clock.h

@@ -62,7 +62,7 @@ class RealTimeClock : public PollingComponent {
   void apply_timezone_();
 #endif
 
-  LazyCallbackManager<void()> time_sync_callback_;
+  CallbackManager<void()> time_sync_callback_;
 };
 
 template<typename... Ts> class TimeHasTimeCondition : public Condition<Ts...> {

esphome/components/udp/__init__.py

@@ -12,8 +12,8 @@ from esphome.components.packet_transport import (
 )
 import esphome.config_validation as cv
 from esphome.const import CONF_DATA, CONF_ID, CONF_PORT, CONF_TRIGGER_ID
-from esphome.core import ID, Lambda
-from esphome.cpp_generator import ExpressionStatement, MockObj
+from esphome.core import ID
+from esphome.cpp_generator import literal
 
 CODEOWNERS = ["@clydebarrow"]
 DEPENDENCIES = ["network"]
@@ -24,6 +24,8 @@ udp_ns = cg.esphome_ns.namespace("udp")
 UDPComponent = udp_ns.class_("UDPComponent", cg.Component)
 UDPWriteAction = udp_ns.class_("UDPWriteAction", automation.Action)
 trigger_args = cg.std_vector.template(cg.uint8)
+trigger_argname = "data"
+trigger_argtype = [(trigger_args, trigger_argname)]
 
 CONF_ADDRESSES = "addresses"
 CONF_LISTEN_ADDRESS = "listen_address"
@@ -111,13 +113,14 @@ async def to_code(config):
     cg.add(var.set_addresses([str(addr) for addr in config[CONF_ADDRESSES]]))
     if on_receive := config.get(CONF_ON_RECEIVE):
         on_receive = on_receive[0]
-        trigger = cg.new_Pvariable(on_receive[CONF_TRIGGER_ID])
+        trigger_id = cg.new_Pvariable(on_receive[CONF_TRIGGER_ID])
         trigger = await automation.build_automation(
-            trigger, [(trigger_args, "data")], on_receive
+            trigger_id, trigger_argtype, on_receive
         )
-        trigger = Lambda(str(ExpressionStatement(trigger.trigger(MockObj("data")))))
-        trigger = await cg.process_lambda(trigger, [(trigger_args, "data")])
-        cg.add(var.add_listener(trigger))
+        trigger_lambda = await cg.process_lambda(
+            trigger.trigger(literal(trigger_argname)), trigger_argtype
+        )
+        cg.add(var.add_listener(trigger_lambda))
         cg.add(var.set_should_listen())
 
 

esphome/components/voice_assistant/voice_assistant.cpp

@@ -430,12 +430,14 @@ void VoiceAssistant::client_subscription(api::APIConnection *client, bool subscr
   }
 
   if (this->api_client_ != nullptr) {
+    char current_peername[socket::SOCKADDR_STR_LEN];
+    char new_peername[socket::SOCKADDR_STR_LEN];
     ESP_LOGE(TAG,
              "Multiple API Clients attempting to connect to Voice Assistant\n"
              "Current client: %s (%s)\n"
              "New client: %s (%s)",
-             this->api_client_->get_name(), this->api_client_->get_peername(), client->get_name(),
-             client->get_peername());
+             this->api_client_->get_name(), this->api_client_->get_peername_to(current_peername), client->get_name(),
+             client->get_peername_to(new_peername));
     return;
   }
 

esphome/core/__init__.py

@@ -278,9 +278,13 @@ LAMBDA_PROG = re.compile(r"\bid\(\s*([a-zA-Z_][a-zA-Z0-9_]*)\s*\)(\.?)")
 
 class Lambda:
     def __init__(self, value):
+        from esphome.cpp_generator import Expression, statement
+
         # pylint: disable=protected-access
         if isinstance(value, Lambda):
             self._value = value._value
+        elif isinstance(value, Expression):
+            self._value = str(statement(value))
         else:
             self._value = value
         self._parts = None

esphome/cpp_generator.py

@@ -462,6 +462,16 @@ def statement(expression: Expression | Statement) -> Statement:
     return ExpressionStatement(expression)
 
 
+def literal(name: str) -> "MockObj":
+    """Create a literal name that will appear in the generated code
+    not surrounded by quotes.
+
+    :param name: The name of the literal.
+    :return: The literal as a MockObj.
+    """
+    return MockObj(name, "")
+
+
 def variable(
     id_: ID, rhs: SafeExpType, type_: "MockObj" = None, register=True
 ) -> "MockObj":
@@ -665,7 +675,7 @@ async def get_variable_with_full_id(id_: ID) -> tuple[ID, "MockObj"]:
 
 
 async def process_lambda(
-    value: Lambda,
+    value: Lambda | Expression,
     parameters: TemplateArgsType,
     capture: str = "",
     return_type: SafeExpType = None,
@@ -689,6 +699,14 @@ async def process_lambda(
 
     if value is None:
         return None
+    # Inadvertently passing a malformed parameters value will lead to the build process mysteriously hanging at the
+    # "Generating C++ source..." stage, so check here to save the developer's hair.
+    assert isinstance(parameters, list) and all(
+        isinstance(p, tuple) and len(p) == 2 for p in parameters
+    )
+    if isinstance(value, Expression):
+        value = Lambda(value)
+
     parts = value.parts[:]
     for i, id in enumerate(value.requires_ids):
         full_id, var = await get_variable_with_full_id(id)

tests/unit_tests/test_cpp_generator.py

@@ -347,3 +347,280 @@ class TestMockObj:
         assert isinstance(actual, cg.MockObj)
         assert actual.base == "foo.eek"
         assert actual.op == "."
+
+
+class TestStatementFunction:
+    """Tests for the statement() function."""
+
+    def test_statement__expression_converted_to_statement(self):
+        """Test that expressions are converted to ExpressionStatement."""
+        expr = cg.RawExpression("foo()")
+        result = cg.statement(expr)
+
+        assert isinstance(result, cg.ExpressionStatement)
+        assert str(result) == "foo();"
+
+    def test_statement__statement_unchanged(self):
+        """Test that statements are returned unchanged."""
+        stmt = cg.RawStatement("foo()")
+        result = cg.statement(stmt)
+
+        assert result is stmt
+        assert str(result) == "foo()"
+
+    def test_statement__expression_statement_unchanged(self):
+        """Test that ExpressionStatement is returned unchanged."""
+        stmt = cg.ExpressionStatement(42)
+        result = cg.statement(stmt)
+
+        assert result is stmt
+        assert str(result) == "42;"
+
+    def test_statement__line_comment_unchanged(self):
+        """Test that LineComment is returned unchanged."""
+        stmt = cg.LineComment("This is a comment")
+        result = cg.statement(stmt)
+
+        assert result is stmt
+        assert str(result) == "// This is a comment"
+
+
+class TestLiteralFunction:
+    """Tests for the literal() function."""
+
+    def test_literal__creates_mockobj(self):
+        """Test that literal() creates a MockObj."""
+        result = cg.literal("MY_CONSTANT")
+
+        assert isinstance(result, cg.MockObj)
+        assert result.base == "MY_CONSTANT"
+        assert result.op == ""
+
+    def test_literal__string_representation(self):
+        """Test that literal names appear unquoted in generated code."""
+        result = cg.literal("nullptr")
+
+        assert str(result) == "nullptr"
+
+    def test_literal__can_be_used_in_expressions(self):
+        """Test that literals can be used as part of larger expressions."""
+        null_lit = cg.literal("nullptr")
+        expr = cg.CallExpression(cg.RawExpression("my_func"), null_lit)
+
+        assert str(expr) == "my_func(nullptr)"
+
+    def test_literal__common_cpp_literals(self):
+        """Test common C++ literal values."""
+        test_cases = [
+            ("nullptr", "nullptr"),
+            ("true", "true"),
+            ("false", "false"),
+            ("NULL", "NULL"),
+            ("NAN", "NAN"),
+        ]
+
+        for name, expected in test_cases:
+            result = cg.literal(name)
+            assert str(result) == expected
+
+
+class TestLambdaConstructor:
+    """Tests for the Lambda class constructor in core/__init__.py."""
+
+    def test_lambda__from_string(self):
+        """Test Lambda constructor with string argument."""
+        from esphome.core import Lambda
+
+        lambda_obj = Lambda("return x + 1;")
+
+        assert lambda_obj.value == "return x + 1;"
+        assert str(lambda_obj) == "return x + 1;"
+
+    def test_lambda__from_expression(self):
+        """Test Lambda constructor with Expression argument."""
+        from esphome.core import Lambda
+
+        expr = cg.RawExpression("x + 1")
+        lambda_obj = Lambda(expr)
+
+        # Expression should be converted to statement (with semicolon)
+        assert lambda_obj.value == "x + 1;"
+
+    def test_lambda__from_lambda(self):
+        """Test Lambda constructor with another Lambda argument."""
+        from esphome.core import Lambda
+
+        original = Lambda("return x + 1;")
+        copy = Lambda(original)
+
+        assert copy.value == original.value
+        assert copy.value == "return x + 1;"
+
+    def test_lambda__parts_parsing(self):
+        """Test that Lambda correctly parses parts with id() references."""
+        from esphome.core import Lambda
+
+        lambda_obj = Lambda("return id(my_sensor).state;")
+        parts = lambda_obj.parts
+
+        # Parts should be split by LAMBDA_PROG regex: text, id, op, text
+        assert len(parts) == 4
+        assert parts[0] == "return "
+        assert parts[1] == "my_sensor"
+        assert parts[2] == "."
+        assert parts[3] == "state;"
+
+    def test_lambda__requires_ids(self):
+        """Test that Lambda correctly extracts required IDs."""
+        from esphome.core import ID, Lambda
+
+        lambda_obj = Lambda("return id(sensor1).state + id(sensor2).value;")
+        ids = lambda_obj.requires_ids
+
+        assert len(ids) == 2
+        assert all(isinstance(id_obj, ID) for id_obj in ids)
+        assert ids[0].id == "sensor1"
+        assert ids[1].id == "sensor2"
+
+    def test_lambda__no_ids(self):
+        """Test Lambda with no id() references."""
+        from esphome.core import Lambda
+
+        lambda_obj = Lambda("return 42;")
+        ids = lambda_obj.requires_ids
+
+        assert len(ids) == 0
+
+    def test_lambda__comment_removal(self):
+        """Test that comments are removed when parsing parts."""
+        from esphome.core import Lambda
+
+        lambda_obj = Lambda("return id(sensor).state; // Get sensor state")
+        parts = lambda_obj.parts
+
+        # Comment should be replaced with space, not affect parsing
+        assert "my_sensor" not in str(parts)
+
+    def test_lambda__multiline_string(self):
+        """Test Lambda with multiline string."""
+        from esphome.core import Lambda
+
+        code = """if (id(sensor).state > 0) {
+  return true;
+}
+return false;"""
+        lambda_obj = Lambda(code)
+
+        assert lambda_obj.value == code
+        assert "sensor" in [id_obj.id for id_obj in lambda_obj.requires_ids]
+
+
+@pytest.mark.asyncio
+class TestProcessLambda:
+    """Tests for the process_lambda() async function."""
+
+    async def test_process_lambda__none_value(self):
+        """Test that None returns None."""
+        result = await cg.process_lambda(None, [])
+
+        assert result is None
+
+    async def test_process_lambda__with_expression(self):
+        """Test process_lambda with Expression argument."""
+
+        expr = cg.RawExpression("return x + 1")
+        result = await cg.process_lambda(expr, [(int, "x")])
+
+        assert isinstance(result, cg.LambdaExpression)
+        assert "x + 1" in str(result)
+
+    async def test_process_lambda__simple_lambda_no_ids(self):
+        """Test process_lambda with simple Lambda without id() references."""
+        from esphome.core import Lambda
+
+        lambda_obj = Lambda("return x + 1;")
+        result = await cg.process_lambda(lambda_obj, [(int, "x")])
+
+        assert isinstance(result, cg.LambdaExpression)
+        # Should have parameter
+        lambda_str = str(result)
+        assert "int32_t x" in lambda_str
+        assert "return x + 1;" in lambda_str
+
+    async def test_process_lambda__with_return_type(self):
+        """Test process_lambda with return type specified."""
+        from esphome.core import Lambda
+
+        lambda_obj = Lambda("return x > 0;")
+        result = await cg.process_lambda(lambda_obj, [(int, "x")], return_type=bool)
+
+        assert isinstance(result, cg.LambdaExpression)
+        lambda_str = str(result)
+        assert "-> bool" in lambda_str
+
+    async def test_process_lambda__with_capture(self):
+        """Test process_lambda with capture specified."""
+        from esphome.core import Lambda
+
+        lambda_obj = Lambda("return captured + x;")
+        result = await cg.process_lambda(lambda_obj, [(int, "x")], capture="captured")
+
+        assert isinstance(result, cg.LambdaExpression)
+        lambda_str = str(result)
+        assert "[captured]" in lambda_str
+
+    async def test_process_lambda__empty_capture(self):
+        """Test process_lambda with empty capture (stateless lambda)."""
+        from esphome.core import Lambda
+
+        lambda_obj = Lambda("return x + 1;")
+        result = await cg.process_lambda(lambda_obj, [(int, "x")], capture="")
+
+        assert isinstance(result, cg.LambdaExpression)
+        lambda_str = str(result)
+        assert "[]" in lambda_str
+
+    async def test_process_lambda__no_parameters(self):
+        """Test process_lambda with no parameters."""
+        from esphome.core import Lambda
+
+        lambda_obj = Lambda("return 42;")
+        result = await cg.process_lambda(lambda_obj, [])
+
+        assert isinstance(result, cg.LambdaExpression)
+        lambda_str = str(result)
+        # Should have empty parameter list
+        assert "()" in lambda_str
+
+    async def test_process_lambda__multiple_parameters(self):
+        """Test process_lambda with multiple parameters."""
+        from esphome.core import Lambda
+
+        lambda_obj = Lambda("return x + y + z;")
+        result = await cg.process_lambda(
+            lambda_obj, [(int, "x"), (float, "y"), (bool, "z")]
+        )
+
+        assert isinstance(result, cg.LambdaExpression)
+        lambda_str = str(result)
+        assert "int32_t x" in lambda_str
+        assert "float y" in lambda_str
+        assert "bool z" in lambda_str
+
+    async def test_process_lambda__parameter_validation(self):
+        """Test that malformed parameters raise assertion error."""
+        from esphome.core import Lambda
+
+        lambda_obj = Lambda("return x;")
+
+        # Test invalid parameter format (not list of tuples)
+        with pytest.raises(AssertionError):
+            await cg.process_lambda(lambda_obj, "invalid")
+
+        # Test invalid tuple format (not 2-element tuples)
+        with pytest.raises(AssertionError):
+            await cg.process_lambda(lambda_obj, [(int, "x", "extra")])
+
+        # Test invalid tuple format (single element)
+        with pytest.raises(AssertionError):
+            await cg.process_lambda(lambda_obj, [(int,)])