tweak comments

Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>
Co-authored-by: Jonathan Swoboda <154711427+swoboda1337@users.noreply.github.com>
Co-authored-by: J. Nick Koston <nick@home-assistant.io>

.clang-tidy.hash

@@ -1 +1 @@
-cf3d341206b4184ec8b7fe85141aef4fe4696aa720c3f8a06d4e57930574bdab
+069fa9526c52f7c580a9ec17c7678d12f142221387e9b561c18f95394d4629a3

esphome/components/esp32/__init__.py

@@ -124,10 +124,14 @@ COMPILER_OPTIMIZATIONS = {
 # - "sdmmc": driver -> esp_driver_sdmmc -> sdmmc dependency chain
 DEFAULT_EXCLUDED_IDF_COMPONENTS = (
     "cmock",  # Unit testing mock framework - ESPHome doesn't use IDF's testing
+    "driver",  # Legacy driver shim - only needed by esp32_touch, esp32_can for legacy headers
     "esp_adc",  # ADC driver - only needed by adc component
+    "esp_driver_dac",  # DAC driver - only needed by esp32_dac component
     "esp_driver_i2s",  # I2S driver - only needed by i2s_audio component
+    "esp_driver_mcpwm",  # MCPWM driver - ESPHome doesn't use motor control PWM
     "esp_driver_rmt",  # RMT driver - only needed by remote_transmitter/receiver, neopixelbus
     "esp_driver_touch_sens",  # Touch sensor driver - only needed by esp32_touch
+    "esp_driver_twai",  # TWAI/CAN driver - only needed by esp32_can component
     "esp_eth",  # Ethernet driver - only needed by ethernet component
     "esp_hid",  # HID host/device support - ESPHome doesn't implement HID functionality
     "esp_http_client",  # HTTP client - only needed by http_request component
@@ -138,9 +142,11 @@ DEFAULT_EXCLUDED_IDF_COMPONENTS = (
     "espcoredump",  # Core dump support - ESPHome has its own debug component
     "fatfs",  # FAT filesystem - ESPHome doesn't use filesystem storage
     "mqtt",  # ESP-IDF MQTT library - ESPHome has its own MQTT implementation
+    "openthread",  # Thread protocol - only needed by openthread component
     "perfmon",  # Xtensa performance monitor - ESPHome has its own debug component
     "protocomm",  # Protocol communication for provisioning - unused by ESPHome
     "spiffs",  # SPIFFS filesystem - ESPHome doesn't use filesystem storage (IDF only)
+    "ulp",  # ULP coprocessor - not currently used by any ESPHome component
     "unity",  # Unit testing framework - ESPHome doesn't use IDF's testing
     "wear_levelling",  # Flash wear levelling for fatfs - unused since fatfs unused
     "wifi_provisioning",  # WiFi provisioning - ESPHome uses its own improv implementation
@@ -739,9 +745,10 @@ CONF_DISABLE_REGI2C_IN_IRAM = "disable_regi2c_in_iram"
 CONF_DISABLE_FATFS = "disable_fatfs"
 
 # VFS requirement tracking
-# Components that need VFS features can call require_vfs_select() or require_vfs_dir()
+# Components that need VFS features can call require_vfs_*() functions
 KEY_VFS_SELECT_REQUIRED = "vfs_select_required"
 KEY_VFS_DIR_REQUIRED = "vfs_dir_required"
+KEY_VFS_TERMIOS_REQUIRED = "vfs_termios_required"
 # Feature requirement tracking - components can call require_* functions to re-enable
 # These are stored in CORE.data[KEY_ESP32] dict
 KEY_USB_SERIAL_JTAG_SECONDARY_REQUIRED = "usb_serial_jtag_secondary_required"
@@ -768,6 +775,15 @@ def require_vfs_dir() -> None:
     CORE.data[KEY_VFS_DIR_REQUIRED] = True
 
 
+def require_vfs_termios() -> None:
+    """Mark that VFS termios support is required by a component.
+
+    Call this from components that use terminal I/O functions (usb_serial_jtag_vfs_*, etc.).
+    This prevents CONFIG_VFS_SUPPORT_TERMIOS from being disabled.
+    """
+    CORE.data[KEY_VFS_TERMIOS_REQUIRED] = True
+
+
 def require_full_certificate_bundle() -> None:
     """Request the full certificate bundle instead of the common-CAs-only bundle.
 
@@ -1372,11 +1388,18 @@ async def to_code(config):
         add_idf_sdkconfig_option("CONFIG_LIBC_LOCKS_PLACE_IN_IRAM", False)
 
     # Disable VFS support for termios (terminal I/O functions)
-    # ESPHome doesn't use termios functions on ESP32 (only used in host UART driver).
+    # USB Serial JTAG VFS functions require termios support.
+    # Components that need it (e.g., logger when USB_SERIAL_JTAG is supported but not selected
+    # as the logger output) call require_vfs_termios().
     # Saves approximately 1.8KB of flash when disabled (default).
-    add_idf_sdkconfig_option(
-        "CONFIG_VFS_SUPPORT_TERMIOS", not advanced[CONF_DISABLE_VFS_SUPPORT_TERMIOS]
-    )
+    if CORE.data.get(KEY_VFS_TERMIOS_REQUIRED, False):
+        # Component requires VFS termios - force enable regardless of user setting
+        add_idf_sdkconfig_option("CONFIG_VFS_SUPPORT_TERMIOS", True)
+    else:
+        # No component needs it - allow user to control (default: disabled)
+        add_idf_sdkconfig_option(
+            "CONFIG_VFS_SUPPORT_TERMIOS", not advanced[CONF_DISABLE_VFS_SUPPORT_TERMIOS]
+        )
 
     # Disable VFS support for select() with file descriptors
     # ESPHome only uses select() with sockets via lwip_select(), which still works.

esphome/components/esp32_can/canbus.py

@@ -15,6 +15,7 @@ from esphome.components.esp32 import (
     VARIANT_ESP32S2,
     VARIANT_ESP32S3,
     get_esp32_variant,
+    include_builtin_idf_component,
 )
 import esphome.config_validation as cv
 from esphome.const import (
@@ -121,6 +122,10 @@ def get_default_tx_enqueue_timeout(bit_rate):
 
 
 async def to_code(config):
+    # Legacy driver component provides driver/twai.h header
+    include_builtin_idf_component("driver")
+    # Also enable esp_driver_twai for future migration to new API
+    include_builtin_idf_component("esp_driver_twai")
     var = cg.new_Pvariable(config[CONF_ID])
     await canbus.register_canbus(var, config)
 

esphome/components/esp32_dac/output.py

@@ -1,7 +1,12 @@
 from esphome import pins
 import esphome.codegen as cg
 from esphome.components import output
-from esphome.components.esp32 import VARIANT_ESP32, VARIANT_ESP32S2, get_esp32_variant
+from esphome.components.esp32 import (
+    VARIANT_ESP32,
+    VARIANT_ESP32S2,
+    get_esp32_variant,
+    include_builtin_idf_component,
+)
 import esphome.config_validation as cv
 from esphome.const import CONF_ID, CONF_NUMBER, CONF_PIN
 
@@ -38,6 +43,7 @@ CONFIG_SCHEMA = output.FLOAT_OUTPUT_SCHEMA.extend(
 
 
 async def to_code(config):
+    include_builtin_idf_component("esp_driver_dac")
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await output.register_output(var, config)

esphome/components/esp32_touch/__init__.py

@@ -269,6 +269,8 @@ CONFIG_SCHEMA = cv.All(
 async def to_code(config):
     # Re-enable ESP-IDF's touch sensor driver (excluded by default to save compile time)
     include_builtin_idf_component("esp_driver_touch_sens")
+    # Legacy driver component provides driver/touch_sensor.h header
+    include_builtin_idf_component("driver")
 
     touch = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(touch, config)

esphome/components/logger/__init__.py

@@ -16,6 +16,8 @@ from esphome.components.esp32 import (
     VARIANT_ESP32S3,
     add_idf_sdkconfig_option,
     get_esp32_variant,
+    require_usb_serial_jtag_secondary,
+    require_vfs_termios,
 )
 from esphome.components.libretiny import get_libretiny_component, get_libretiny_family
 from esphome.components.libretiny.const import (
@@ -397,9 +399,15 @@ async def to_code(config):
         elif config[CONF_HARDWARE_UART] == USB_SERIAL_JTAG:
             add_idf_sdkconfig_option("CONFIG_ESP_CONSOLE_USB_SERIAL_JTAG", True)
             cg.add_define("USE_LOGGER_UART_SELECTION_USB_SERIAL_JTAG")
+    # Define platform support flags for components that need auto-detection
     try:
         uart_selection(USB_SERIAL_JTAG)
         cg.add_define("USE_LOGGER_USB_SERIAL_JTAG")
+        # USB Serial JTAG code is compiled when platform supports it.
+        # Enable secondary USB serial JTAG console so the VFS functions are available.
+        if CORE.is_esp32 and config[CONF_HARDWARE_UART] != USB_SERIAL_JTAG:
+            require_usb_serial_jtag_secondary()
+            require_vfs_termios()
     except cv.Invalid:
         pass
     try:

esphome/components/mipi_spi/mipi_spi.cpp

@@ -1,6 +1,39 @@
 #include "mipi_spi.h"
 #include "esphome/core/log.h"
 
-namespace esphome {
-namespace mipi_spi {}  // namespace mipi_spi
-}  // namespace esphome
+namespace esphome::mipi_spi {
+
+void internal_dump_config(const char *model, int width, int height, int offset_width, int offset_height, uint8_t madctl,
+                          bool invert_colors, int display_bits, bool is_big_endian, const optional<uint8_t> &brightness,
+                          GPIOPin *cs, GPIOPin *reset, GPIOPin *dc, int spi_mode, uint32_t data_rate, int bus_width) {
+  ESP_LOGCONFIG(TAG,
+                "MIPI_SPI Display\n"
+                "  Model: %s\n"
+                "  Width: %d\n"
+                "  Height: %d\n"
+                "  Swap X/Y: %s\n"
+                "  Mirror X: %s\n"
+                "  Mirror Y: %s\n"
+                "  Invert colors: %s\n"
+                "  Color order: %s\n"
+                "  Display pixels: %d bits\n"
+                "  Endianness: %s\n"
+                "  SPI Mode: %d\n"
+                "  SPI Data rate: %uMHz\n"
+                "  SPI Bus width: %d",
+                model, width, height, YESNO(madctl & MADCTL_MV), YESNO(madctl & (MADCTL_MX | MADCTL_XFLIP)),
+                YESNO(madctl & (MADCTL_MY | MADCTL_YFLIP)), YESNO(invert_colors), (madctl & MADCTL_BGR) ? "BGR" : "RGB",
+                display_bits, is_big_endian ? "Big" : "Little", spi_mode, static_cast<unsigned>(data_rate / 1000000),
+                bus_width);
+  LOG_PIN("  CS Pin: ", cs);
+  LOG_PIN("  Reset Pin: ", reset);
+  LOG_PIN("  DC Pin: ", dc);
+  if (offset_width != 0)
+    ESP_LOGCONFIG(TAG, "  Offset width: %d", offset_width);
+  if (offset_height != 0)
+    ESP_LOGCONFIG(TAG, "  Offset height: %d", offset_height);
+  if (brightness.has_value())
+    ESP_LOGCONFIG(TAG, "  Brightness: %u", brightness.value());
+}
+
+}  // namespace esphome::mipi_spi

esphome/components/mipi_spi/mipi_spi.h

@@ -63,6 +63,11 @@ enum BusType {
   BUS_TYPE_SINGLE_16 = 16,  // Single bit bus, but 16 bits per transfer
 };
 
+// Helper function for dump_config - defined in mipi_spi.cpp to allow use of LOG_PIN macro
+void internal_dump_config(const char *model, int width, int height, int offset_width, int offset_height, uint8_t madctl,
+                          bool invert_colors, int display_bits, bool is_big_endian, const optional<uint8_t> &brightness,
+                          GPIOPin *cs, GPIOPin *reset, GPIOPin *dc, int spi_mode, uint32_t data_rate, int bus_width);
+
 /**
  * Base class for MIPI SPI displays.
  * All the methods are defined here in the header file, as it is not possible to define templated methods in a cpp file.
@@ -201,37 +206,9 @@ class MipiSpi : public display::Display,
   }
 
   void dump_config() override {
-    esph_log_config(TAG,
-                    "MIPI_SPI Display\n"
-                    "  Model: %s\n"
-                    "  Width: %u\n"
-                    "  Height: %u",
-                    this->model_, WIDTH, HEIGHT);
-    if constexpr (OFFSET_WIDTH != 0)
-      esph_log_config(TAG, "  Offset width: %u", OFFSET_WIDTH);
-    if constexpr (OFFSET_HEIGHT != 0)
-      esph_log_config(TAG, "  Offset height: %u", OFFSET_HEIGHT);
-    esph_log_config(TAG,
-                    "  Swap X/Y: %s\n"
-                    "  Mirror X: %s\n"
-                    "  Mirror Y: %s\n"
-                    "  Invert colors: %s\n"
-                    "  Color order: %s\n"
-                    "  Display pixels: %d bits\n"
-                    "  Endianness: %s\n",
-                    YESNO(this->madctl_ & MADCTL_MV), YESNO(this->madctl_ & (MADCTL_MX | MADCTL_XFLIP)),
-                    YESNO(this->madctl_ & (MADCTL_MY | MADCTL_YFLIP)), YESNO(this->invert_colors_),
-                    this->madctl_ & MADCTL_BGR ? "BGR" : "RGB", DISPLAYPIXEL * 8, IS_BIG_ENDIAN ? "Big" : "Little");
-    if (this->brightness_.has_value())
-      esph_log_config(TAG, "  Brightness: %u", this->brightness_.value());
-    log_pin(TAG, "  CS Pin: ", this->cs_);
-    log_pin(TAG, "  Reset Pin: ", this->reset_pin_);
-    log_pin(TAG, "  DC Pin: ", this->dc_pin_);
-    esph_log_config(TAG,
-                    "  SPI Mode: %d\n"
-                    "  SPI Data rate: %dMHz\n"
-                    "  SPI Bus width: %d",
-                    this->mode_, static_cast<unsigned>(this->data_rate_ / 1000000), BUS_TYPE);
+    internal_dump_config(this->model_, WIDTH, HEIGHT, OFFSET_WIDTH, OFFSET_HEIGHT, this->madctl_, this->invert_colors_,
+                         DISPLAYPIXEL * 8, IS_BIG_ENDIAN, this->brightness_, this->cs_, this->reset_pin_, this->dc_pin_,
+                         this->mode_, this->data_rate_, BUS_TYPE);
   }
 
  protected:

esphome/components/mqtt/mqtt_client.cpp

@@ -643,10 +643,34 @@ static bool topic_match(const char *message, const char *subscription) {
 }
 
 void MQTTClientComponent::on_message(const std::string &topic, const std::string &payload) {
-  for (auto &subscription : this->subscriptions_) {
-    if (topic_match(topic.c_str(), subscription.topic.c_str()))
-      subscription.callback(topic, payload);
-  }
+#ifdef USE_ESP8266
+  // IMPORTANT: This defer is REQUIRED to prevent stack overflow crashes on ESP8266.
+  //
+  // On ESP8266, this callback is invoked directly from the lwIP/AsyncTCP network stack
+  // which runs in the "sys" context with a very limited stack (~4KB). By the time we
+  // reach this function, the stack is already partially consumed by the network
+  // processing chain: tcp_input -> AsyncClient::_recv -> AsyncMqttClient::_onMessage -> here.
+  //
+  // MQTT subscription callbacks can trigger arbitrary user actions (automations, HTTP
+  // requests, sensor updates, etc.) which may have deep call stacks of their own.
+  // For example, an HTTP request action requires: DNS lookup -> TCP connect -> TLS
+  // handshake (if HTTPS) -> request formatting. This easily overflows the remaining
+  // system stack space, causing a LoadStoreAlignmentCause exception or silent corruption.
+  //
+  // By deferring to the main loop, we ensure callbacks execute with a fresh, full-size
+  // stack in the normal application context rather than the constrained network task.
+  //
+  // DO NOT REMOVE THIS DEFER without understanding the above. It may appear to work
+  // in simple tests but will cause crashes with complex automations.
+  this->defer([this, topic, payload]() {
+#endif
+    for (auto &subscription : this->subscriptions_) {
+      if (topic_match(topic.c_str(), subscription.topic.c_str()))
+        subscription.callback(topic, payload);
+    }
+#ifdef USE_ESP8266
+  });
+#endif
 }
 
 // Setters

esphome/components/openthread/__init__.py

@@ -4,6 +4,7 @@ from esphome.components.esp32 import (
     VARIANT_ESP32C6,
     VARIANT_ESP32H2,
     add_idf_sdkconfig_option,
+    include_builtin_idf_component,
     only_on_variant,
     require_vfs_select,
 )
@@ -172,6 +173,9 @@ FINAL_VALIDATE_SCHEMA = _final_validate
 
 
 async def to_code(config):
+    # Re-enable openthread IDF component (excluded by default)
+    include_builtin_idf_component("openthread")
+
     cg.add_define("USE_OPENTHREAD")
 
     # OpenThread SRP needs access to mDNS services after setup

esphome/components/pmsx003/pmsx003.cpp

@@ -2,21 +2,20 @@
 #include "esphome/core/log.h"
 #include "esphome/core/application.h"
 
-namespace esphome {
-namespace pmsx003 {
+namespace esphome::pmsx003 {
 
 static const char *const TAG = "pmsx003";
 
 static const uint8_t START_CHARACTER_1 = 0x42;
 static const uint8_t START_CHARACTER_2 = 0x4D;
 
-static const uint16_t PMS_STABILISING_MS = 30000;  // time taken for the sensor to become stable after power on in ms
+static const uint16_t STABILISING_MS = 30000;  // time taken for the sensor to become stable after power on in ms
 
-static const uint16_t PMS_CMD_MEASUREMENT_MODE_PASSIVE =
-    0x0000;  // use `PMS_CMD_MANUAL_MEASUREMENT` to trigger a measurement
-static const uint16_t PMS_CMD_MEASUREMENT_MODE_ACTIVE = 0x0001;  // automatically perform measurements
-static const uint16_t PMS_CMD_SLEEP_MODE_SLEEP = 0x0000;         // go to sleep mode
-static const uint16_t PMS_CMD_SLEEP_MODE_WAKEUP = 0x0001;        // wake up from sleep mode
+static const uint16_t CMD_MEASUREMENT_MODE_PASSIVE =
+    0x0000;  // use `Command::MANUAL_MEASUREMENT` to trigger a measurement
+static const uint16_t CMD_MEASUREMENT_MODE_ACTIVE = 0x0001;  // automatically perform measurements
+static const uint16_t CMD_SLEEP_MODE_SLEEP = 0x0000;         // go to sleep mode
+static const uint16_t CMD_SLEEP_MODE_WAKEUP = 0x0001;        // wake up from sleep mode
 
 void PMSX003Component::setup() {}
 
@@ -42,7 +41,7 @@ void PMSX003Component::dump_config() {
   LOG_SENSOR("  ", "Temperature", this->temperature_sensor_);
   LOG_SENSOR("  ", "Humidity", this->humidity_sensor_);
 
-  if (this->update_interval_ <= PMS_STABILISING_MS) {
+  if (this->update_interval_ <= STABILISING_MS) {
     ESP_LOGCONFIG(TAG, "  Mode: active continuous (sensor default)");
   } else {
     ESP_LOGCONFIG(TAG, "  Mode: passive with sleep/wake cycles");
@@ -55,44 +54,44 @@ void PMSX003Component::loop() {
   const uint32_t now = App.get_loop_component_start_time();
 
   // Initialize sensor mode on first loop
-  if (this->initialised_ == 0) {
-    if (this->update_interval_ > PMS_STABILISING_MS) {
+  if (!this->initialised_) {
+    if (this->update_interval_ > STABILISING_MS) {
       // Long update interval: use passive mode with sleep/wake cycles
-      this->send_command_(PMS_CMD_MEASUREMENT_MODE, PMS_CMD_MEASUREMENT_MODE_PASSIVE);
-      this->send_command_(PMS_CMD_SLEEP_MODE, PMS_CMD_SLEEP_MODE_WAKEUP);
+      this->send_command_(Command::MEASUREMENT_MODE, CMD_MEASUREMENT_MODE_PASSIVE);
+      this->send_command_(Command::SLEEP_MODE, CMD_SLEEP_MODE_WAKEUP);
     } else {
       // Short/zero update interval: use active continuous mode
-      this->send_command_(PMS_CMD_MEASUREMENT_MODE, PMS_CMD_MEASUREMENT_MODE_ACTIVE);
+      this->send_command_(Command::MEASUREMENT_MODE, CMD_MEASUREMENT_MODE_ACTIVE);
     }
-    this->initialised_ = 1;
+    this->initialised_ = true;
   }
 
   // If we update less often than it takes the device to stabilise, spin the fan down
   // rather than running it constantly. It does take some time to stabilise, so we
   // need to keep track of what state we're in.
-  if (this->update_interval_ > PMS_STABILISING_MS) {
+  if (this->update_interval_ > STABILISING_MS) {
     switch (this->state_) {
-      case PMSX003_STATE_IDLE:
+      case State::IDLE:
         // Power on the sensor now so it'll be ready when we hit the update time
-        if (now - this->last_update_ < (this->update_interval_ - PMS_STABILISING_MS))
+        if (now - this->last_update_ < (this->update_interval_ - STABILISING_MS))
           return;
 
-        this->state_ = PMSX003_STATE_STABILISING;
-        this->send_command_(PMS_CMD_SLEEP_MODE, PMS_CMD_SLEEP_MODE_WAKEUP);
+        this->state_ = State::STABILISING;
+        this->send_command_(Command::SLEEP_MODE, CMD_SLEEP_MODE_WAKEUP);
         this->fan_on_time_ = now;
         return;
-      case PMSX003_STATE_STABILISING:
+      case State::STABILISING:
         // wait for the sensor to be stable
-        if (now - this->fan_on_time_ < PMS_STABILISING_MS)
+        if (now - this->fan_on_time_ < STABILISING_MS)
           return;
         // consume any command responses that are in the serial buffer
         while (this->available())
           this->read_byte(&this->data_[0]);
         // Trigger a new read
-        this->send_command_(PMS_CMD_MANUAL_MEASUREMENT, 0);
-        this->state_ = PMSX003_STATE_WAITING;
+        this->send_command_(Command::MANUAL_MEASUREMENT, 0);
+        this->state_ = State::WAITING;
         break;
-      case PMSX003_STATE_WAITING:
+      case State::WAITING:
         // Just go ahead and read stuff
         break;
     }
@@ -180,27 +179,31 @@ optional<bool> PMSX003Component::check_byte_() {
 }
 
 bool PMSX003Component::check_payload_length_(uint16_t payload_length) {
+  // https://avaldebe.github.io/PyPMS/sensors/Plantower/
   switch (this->type_) {
-    case PMSX003_TYPE_X003:
-      // The expected payload length is typically 28 bytes.
-      // However, a 20-byte payload check was already present in the code.
-      // No official documentation was found confirming this.
-      // Retaining this check to avoid breaking existing behavior.
+    case Type::PMS1003:
+      return payload_length == 28;  // 2*13+2
+    case Type::PMS3003:             // Data 7/8/9 not set/reserved
+      return payload_length == 20;  // 2*9+2
+    case Type::PMSX003:             // Data 13 not set/reserved
+      // Deprecated: Length 20 is for PMS3003 backwards compatibility
       return payload_length == 28 || payload_length == 20;  // 2*13+2
-    case PMSX003_TYPE_5003T:
-    case PMSX003_TYPE_5003S:
-      return payload_length == 28;  // 2*13+2 (Data 13 not set/reserved)
-    case PMSX003_TYPE_5003ST:
-      return payload_length == 36;  // 2*17+2 (Data 16 not set/reserved)
+    case Type::PMS5003S:
+    case Type::PMS5003T:            // Data 13 not set/reserved
+      return payload_length == 28;  // 2*13+2
+    case Type::PMS5003ST:           // Data 16 not set/reserved
+      return payload_length == 36;  // 2*17+2
+    case Type::PMS9003M:
+      return payload_length == 28;  // 2*13+2
   }
   return false;
 }
 
-void PMSX003Component::send_command_(PMSX0003Command cmd, uint16_t data) {
+void PMSX003Component::send_command_(Command cmd, uint16_t data) {
   uint8_t send_data[7] = {
       START_CHARACTER_1,            // Start Byte 1
       START_CHARACTER_2,            // Start Byte 2
-      cmd,                          // Command
+      static_cast<uint8_t>(cmd),    // Command
       uint8_t((data >> 8) & 0xFF),  // Data 1
       uint8_t((data >> 0) & 0xFF),  // Data 2
       0,                            // Verify Byte 1
@@ -265,7 +268,7 @@ void PMSX003Component::parse_data_() {
   if (this->pm_particles_25um_sensor_ != nullptr)
     this->pm_particles_25um_sensor_->publish_state(pm_particles_25um);
 
-  if (this->type_ == PMSX003_TYPE_5003T) {
+  if (this->type_ == Type::PMS5003T) {
     ESP_LOGD(TAG,
              "Got PM0.3 Particles: %u Count/0.1L, PM0.5 Particles: %u Count/0.1L, PM1.0 Particles: %u Count/0.1L, "
              "PM2.5 Particles %u Count/0.1L",
@@ -289,7 +292,7 @@ void PMSX003Component::parse_data_() {
   }
 
   // Formaldehyde
-  if (this->type_ == PMSX003_TYPE_5003ST || this->type_ == PMSX003_TYPE_5003S) {
+  if (this->type_ == Type::PMS5003S || this->type_ == Type::PMS5003ST) {
     const uint16_t formaldehyde = this->get_16_bit_uint_(28);
 
     ESP_LOGD(TAG, "Got Formaldehyde: %u µg/m^3", formaldehyde);
@@ -299,8 +302,8 @@ void PMSX003Component::parse_data_() {
   }
 
   // Temperature and Humidity
-  if (this->type_ == PMSX003_TYPE_5003ST || this->type_ == PMSX003_TYPE_5003T) {
-    const uint8_t temperature_offset = (this->type_ == PMSX003_TYPE_5003T) ? 24 : 30;
+  if (this->type_ == Type::PMS5003T || this->type_ == Type::PMS5003ST) {
+    const uint8_t temperature_offset = (this->type_ == Type::PMS5003T) ? 24 : 30;
 
     const float temperature = static_cast<int16_t>(this->get_16_bit_uint_(temperature_offset)) / 10.0f;
     const float humidity = this->get_16_bit_uint_(temperature_offset + 2) / 10.0f;
@@ -314,22 +317,22 @@ void PMSX003Component::parse_data_() {
   }
 
   // Firmware Version and Error Code
-  if (this->type_ == PMSX003_TYPE_5003ST) {
-    const uint8_t firmware_version = this->data_[36];
-    const uint8_t error_code = this->data_[37];
+  if (this->type_ == Type::PMS1003 || this->type_ == Type::PMS5003ST || this->type_ == Type::PMS9003M) {
+    const uint8_t firmware_error_code_offset = (this->type_ == Type::PMS5003ST) ? 36 : 28;
+    const uint8_t firmware_version = this->data_[firmware_error_code_offset];
+    const uint8_t error_code = this->data_[firmware_error_code_offset + 1];
 
     ESP_LOGD(TAG, "Got Firmware Version: 0x%02X, Error Code: 0x%02X", firmware_version, error_code);
   }
 
   // Spin down the sensor again if we aren't going to need it until more time has
   // passed than it takes to stabilise
-  if (this->update_interval_ > PMS_STABILISING_MS) {
-    this->send_command_(PMS_CMD_SLEEP_MODE, PMS_CMD_SLEEP_MODE_SLEEP);
-    this->state_ = PMSX003_STATE_IDLE;
+  if (this->update_interval_ > STABILISING_MS) {
+    this->send_command_(Command::SLEEP_MODE, CMD_SLEEP_MODE_SLEEP);
+    this->state_ = State::IDLE;
   }
 
   this->status_clear_warning();
 }
 
-}  // namespace pmsx003
-}  // namespace esphome
+}  // namespace esphome::pmsx003

esphome/components/pmsx003/pmsx003.h

@@ -5,27 +5,28 @@
 #include "esphome/components/sensor/sensor.h"
 #include "esphome/components/uart/uart.h"
 
-namespace esphome {
-namespace pmsx003 {
+namespace esphome::pmsx003 {
 
-enum PMSX0003Command : uint8_t {
-  PMS_CMD_MEASUREMENT_MODE =
-      0xE1,  // Data Options: `PMS_CMD_MEASUREMENT_MODE_PASSIVE`, `PMS_CMD_MEASUREMENT_MODE_ACTIVE`
-  PMS_CMD_MANUAL_MEASUREMENT = 0xE2,
-  PMS_CMD_SLEEP_MODE = 0xE4,  // Data Options: `PMS_CMD_SLEEP_MODE_SLEEP`, `PMS_CMD_SLEEP_MODE_WAKEUP`
+enum class Type : uint8_t {
+  PMS1003 = 0,
+  PMS3003,
+  PMSX003,  // PMS5003, PMS6003, PMS7003, PMSA003 (NOT PMSA003I - see `pmsa003i` component)
+  PMS5003S,
+  PMS5003T,
+  PMS5003ST,
+  PMS9003M,
 };
 
-enum PMSX003Type {
-  PMSX003_TYPE_X003 = 0,
-  PMSX003_TYPE_5003T,
-  PMSX003_TYPE_5003ST,
-  PMSX003_TYPE_5003S,
+enum class Command : uint8_t {
+  MEASUREMENT_MODE = 0xE1,  // Data Options: `CMD_MEASUREMENT_MODE_PASSIVE`, `CMD_MEASUREMENT_MODE_ACTIVE`
+  MANUAL_MEASUREMENT = 0xE2,
+  SLEEP_MODE = 0xE4,  // Data Options: `CMD_SLEEP_MODE_SLEEP`, `CMD_SLEEP_MODE_WAKEUP`
 };
 
-enum PMSX003State {
-  PMSX003_STATE_IDLE = 0,
-  PMSX003_STATE_STABILISING,
-  PMSX003_STATE_WAITING,
+enum class State : uint8_t {
+  IDLE = 0,
+  STABILISING,
+  WAITING,
 };
 
 class PMSX003Component : public uart::UARTDevice, public Component {
@@ -37,7 +38,7 @@ class PMSX003Component : public uart::UARTDevice, public Component {
 
   void set_update_interval(uint32_t update_interval) { this->update_interval_ = update_interval; }
 
-  void set_type(PMSX003Type type) { this->type_ = type; }
+  void set_type(Type type) { this->type_ = type; }
 
   void set_pm_1_0_std_sensor(sensor::Sensor *pm_1_0_std_sensor) { this->pm_1_0_std_sensor_ = pm_1_0_std_sensor; }
   void set_pm_2_5_std_sensor(sensor::Sensor *pm_2_5_std_sensor) { this->pm_2_5_std_sensor_ = pm_2_5_std_sensor; }
@@ -77,20 +78,20 @@ class PMSX003Component : public uart::UARTDevice, public Component {
   optional<bool> check_byte_();
   void parse_data_();
   bool check_payload_length_(uint16_t payload_length);
-  void send_command_(PMSX0003Command cmd, uint16_t data);
+  void send_command_(Command cmd, uint16_t data);
   uint16_t get_16_bit_uint_(uint8_t start_index) const {
     return encode_uint16(this->data_[start_index], this->data_[start_index + 1]);
   }
 
+  Type type_;
+  State state_{State::IDLE};
+  bool initialised_{false};
   uint8_t data_[64];
   uint8_t data_index_{0};
-  uint8_t initialised_{0};
   uint32_t fan_on_time_{0};
   uint32_t last_update_{0};
   uint32_t last_transmission_{0};
   uint32_t update_interval_{0};
-  PMSX003State state_{PMSX003_STATE_IDLE};
-  PMSX003Type type_;
 
   // "Standard Particle"
   sensor::Sensor *pm_1_0_std_sensor_{nullptr};
@@ -118,5 +119,4 @@ class PMSX003Component : public uart::UARTDevice, public Component {
   sensor::Sensor *humidity_sensor_{nullptr};
 };
 
-}  // namespace pmsx003
-}  // namespace esphome
+}  // namespace esphome::pmsx003

esphome/components/pmsx003/sensor.py

@@ -40,34 +40,128 @@ pmsx003_ns = cg.esphome_ns.namespace("pmsx003")
 PMSX003Component = pmsx003_ns.class_("PMSX003Component", uart.UARTDevice, cg.Component)
 PMSX003Sensor = pmsx003_ns.class_("PMSX003Sensor", sensor.Sensor)
 
-TYPE_PMSX003 = "PMSX003"
+TYPE_PMS1003 = "PMS1003"
+TYPE_PMS3003 = "PMS3003"
+TYPE_PMSX003 = "PMSX003"  # PMS5003, PMS6003, PMS7003, PMSA003 (NOT PMSA003I - see `pmsa003i` component)
+TYPE_PMS5003S = "PMS5003S"
 TYPE_PMS5003T = "PMS5003T"
 TYPE_PMS5003ST = "PMS5003ST"
-TYPE_PMS5003S = "PMS5003S"
+TYPE_PMS9003M = "PMS9003M"
 
-PMSX003Type = pmsx003_ns.enum("PMSX003Type")
+Type = pmsx003_ns.enum("Type", is_class=True)
 
 PMSX003_TYPES = {
-    TYPE_PMSX003: PMSX003Type.PMSX003_TYPE_X003,
-    TYPE_PMS5003T: PMSX003Type.PMSX003_TYPE_5003T,
-    TYPE_PMS5003ST: PMSX003Type.PMSX003_TYPE_5003ST,
-    TYPE_PMS5003S: PMSX003Type.PMSX003_TYPE_5003S,
+    TYPE_PMS1003: Type.PMS1003,
+    TYPE_PMS3003: Type.PMS3003,
+    TYPE_PMSX003: Type.PMSX003,
+    TYPE_PMS5003S: Type.PMS5003S,
+    TYPE_PMS5003T: Type.PMS5003T,
+    TYPE_PMS5003ST: Type.PMS5003ST,
+    TYPE_PMS9003M: Type.PMS9003M,
 }
 
 SENSORS_TO_TYPE = {
-    CONF_PM_1_0: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_2_5: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_10_0: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_1_0_STD: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_2_5_STD: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_10_0_STD: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_0_3UM: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_0_5UM: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_1_0UM: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_2_5UM: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_5_0UM: [TYPE_PMSX003, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_10_0UM: [TYPE_PMSX003, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_FORMALDEHYDE: [TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_PM_1_0_STD: [
+        TYPE_PMS1003,
+        TYPE_PMS3003,
+        TYPE_PMSX003,
+        TYPE_PMS5003S,
+        TYPE_PMS5003T,
+        TYPE_PMS5003ST,
+        TYPE_PMS9003M,
+    ],
+    CONF_PM_2_5_STD: [
+        TYPE_PMS1003,
+        TYPE_PMS3003,
+        TYPE_PMSX003,
+        TYPE_PMS5003S,
+        TYPE_PMS5003T,
+        TYPE_PMS5003ST,
+        TYPE_PMS9003M,
+    ],
+    CONF_PM_10_0_STD: [
+        TYPE_PMS1003,
+        TYPE_PMS3003,
+        TYPE_PMSX003,
+        TYPE_PMS5003S,
+        TYPE_PMS5003T,
+        TYPE_PMS5003ST,
+        TYPE_PMS9003M,
+    ],
+    CONF_PM_1_0: [
+        TYPE_PMS1003,
+        TYPE_PMS3003,
+        TYPE_PMSX003,
+        TYPE_PMS5003S,
+        TYPE_PMS5003T,
+        TYPE_PMS5003ST,
+        TYPE_PMS9003M,
+    ],
+    CONF_PM_2_5: [
+        TYPE_PMS1003,
+        TYPE_PMS3003,
+        TYPE_PMSX003,
+        TYPE_PMS5003S,
+        TYPE_PMS5003T,
+        TYPE_PMS5003ST,
+        TYPE_PMS9003M,
+    ],
+    CONF_PM_10_0: [
+        TYPE_PMS1003,
+        TYPE_PMS3003,
+        TYPE_PMSX003,
+        TYPE_PMS5003S,
+        TYPE_PMS5003T,
+        TYPE_PMS5003ST,
+        TYPE_PMS9003M,
+    ],
+    CONF_PM_0_3UM: [
+        TYPE_PMS1003,
+        TYPE_PMSX003,
+        TYPE_PMS5003S,
+        TYPE_PMS5003T,
+        TYPE_PMS5003ST,
+        TYPE_PMS9003M,
+    ],
+    CONF_PM_0_5UM: [
+        TYPE_PMS1003,
+        TYPE_PMSX003,
+        TYPE_PMS5003S,
+        TYPE_PMS5003T,
+        TYPE_PMS5003ST,
+        TYPE_PMS9003M,
+    ],
+    CONF_PM_1_0UM: [
+        TYPE_PMS1003,
+        TYPE_PMSX003,
+        TYPE_PMS5003S,
+        TYPE_PMS5003T,
+        TYPE_PMS5003ST,
+        TYPE_PMS9003M,
+    ],
+    CONF_PM_2_5UM: [
+        TYPE_PMS1003,
+        TYPE_PMSX003,
+        TYPE_PMS5003S,
+        TYPE_PMS5003T,
+        TYPE_PMS5003ST,
+        TYPE_PMS9003M,
+    ],
+    CONF_PM_5_0UM: [
+        TYPE_PMS1003,
+        TYPE_PMSX003,
+        TYPE_PMS5003S,
+        TYPE_PMS5003ST,
+        TYPE_PMS9003M,
+    ],
+    CONF_PM_10_0UM: [
+        TYPE_PMS1003,
+        TYPE_PMSX003,
+        TYPE_PMS5003S,
+        TYPE_PMS5003ST,
+        TYPE_PMS9003M,
+    ],
+    CONF_FORMALDEHYDE: [TYPE_PMS5003S, TYPE_PMS5003ST],
     CONF_TEMPERATURE: [TYPE_PMS5003T, TYPE_PMS5003ST],
     CONF_HUMIDITY: [TYPE_PMS5003T, TYPE_PMS5003ST],
 }

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/web_server_base/__init__.py

@@ -53,4 +53,4 @@ async def to_code(config):
                 "lib_ignore", ["ESPAsyncTCP", "AsyncTCP", "AsyncTCP_RP2040W"]
             )
         # https://github.com/ESP32Async/ESPAsyncWebServer/blob/main/library.json
-        cg.add_library("ESP32Async/ESPAsyncWebServer", "3.9.5")
+        cg.add_library("ESP32Async/ESPAsyncWebServer", "3.9.6")

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/core/application.cpp

@@ -210,7 +210,7 @@ void Application::loop() {
 #ifdef USE_ESP32
       esp_chip_info_t chip_info;
       esp_chip_info(&chip_info);
-      ESP_LOGI(TAG, "ESP32 Chip: %s r%d.%d, %d core(s)", ESPHOME_VARIANT, chip_info.revision / 100,
+      ESP_LOGI(TAG, "ESP32 Chip: %s rev%d.%d, %d core(s)", ESPHOME_VARIANT, chip_info.revision / 100,
                chip_info.revision % 100, chip_info.cores);
 #if defined(USE_ESP32_VARIANT_ESP32) && !defined(USE_ESP32_MIN_CHIP_REVISION_SET)
       // Suggest optimization for chips that don't need the PSRAM cache workaround

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)

platformio.ini

@@ -114,7 +114,7 @@ lib_deps =
     ESP8266WiFi                           ; wifi (Arduino built-in)
     Update                                ; ota (Arduino built-in)
     ESP32Async/ESPAsyncTCP@2.0.0          ; async_tcp
-    ESP32Async/ESPAsyncWebServer@3.9.5    ; web_server_base
+    ESP32Async/ESPAsyncWebServer@3.9.6    ; web_server_base
     makuna/NeoPixelBus@2.7.3              ; neopixelbus
     ESP8266HTTPClient                     ; http_request (Arduino built-in)
     ESP8266mDNS                           ; mdns (Arduino built-in)
@@ -202,7 +202,7 @@ lib_deps =
     ${common:arduino.lib_deps}
     ayushsharma82/RPAsyncTCP@1.3.2        ; async_tcp
     bblanchon/ArduinoJson@7.4.2           ; json
-    ESP32Async/ESPAsyncWebServer@3.9.5    ; web_server_base
+    ESP32Async/ESPAsyncWebServer@3.9.6    ; web_server_base
 build_flags =
     ${common:arduino.build_flags}
     -DUSE_RP2040
@@ -218,7 +218,7 @@ framework = arduino
 lib_compat_mode = soft
 lib_deps =
     bblanchon/ArduinoJson@7.4.2           ; json
-    ESP32Async/ESPAsyncWebServer@3.9.5    ; web_server_base
+    ESP32Async/ESPAsyncWebServer@3.9.6    ; web_server_base
     droscy/esp_wireguard@0.4.2            ; wireguard
 build_flags =
     ${common:arduino.build_flags}

tests/components/mipi_spi/test.esp8266-ard.yaml

@@ -0,0 +1,10 @@
+substitutions:
+  dc_pin: GPIO15
+  cs_pin: GPIO5
+  enable_pin: GPIO4
+  reset_pin: GPIO16
+
+packages:
+  spi: !include ../../test_build_components/common/spi/esp8266-ard.yaml
+
+<<: !include common.yaml

tests/components/pmsx003/common.yaml

@@ -8,11 +8,11 @@ sensor:
     pm_10_0:
       name: PM 10.0 Concentration
     pm_1_0_std:
-      name: PM 1.0 Standard Atmospher Concentration
+      name: PM 1.0 Standard Atmospheric Concentration
     pm_2_5_std:
-      name: PM 2.5 Standard Atmospher Concentration
+      name: PM 2.5 Standard Atmospheric Concentration
     pm_10_0_std:
-      name: PM 10.0 Standard Atmospher Concentration
+      name: PM 10.0 Standard Atmospheric Concentration
     pm_0_3um:
       name: Particulate Count >0.3um
     pm_0_5um:

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,)])