[nextion] Replace connect_info vector with fixed-size field parser, always log device info (#16059)

Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>

esphome/components/nextion/display.py

@@ -1,3 +1,5 @@
+import logging
+
 from esphome import automation
 import esphome.codegen as cg
 from esphome.components import display, esp32, uart
@@ -39,6 +41,8 @@ from .base_component import (
     CONF_WAKE_UP_PAGE,
 )
 
+_LOGGER = logging.getLogger(__name__)
+
 CODEOWNERS = ["@senexcrenshaw", "@edwardtfn"]
 DEPENDENCIES = ["uart"]
 
@@ -55,6 +59,15 @@ NextionSetBrightnessAction = nextion_ns.class_(
 )
 
 
+def _deprecated_dump_device_info(value):
+    _LOGGER.warning(
+        "'dump_device_info' is deprecated and will be removed in ESPHome 2026.11.0. "
+        "Device info is now always logged at connection time. "
+        "Please remove this option from your configuration."
+    )
+    return value
+
+
 def _validate_tft_upload(config):
     has_tft_url = CONF_TFT_URL in config
     for conf_key in (
@@ -81,7 +94,10 @@ CONFIG_SCHEMA = cv.All(
                 cv.positive_time_period_milliseconds,
                 cv.Range(max=TimePeriod(milliseconds=255)),
             ),
-            cv.Optional(CONF_DUMP_DEVICE_INFO, default=False): cv.boolean,
+            # Deprecated — device info is now always logged. Remove before 2026.11.0.
+            cv.Optional(CONF_DUMP_DEVICE_INFO): cv.All(
+                cv.boolean, _deprecated_dump_device_info
+            ),
             cv.Optional(CONF_EXIT_REPARSE_ON_START, default=False): cv.boolean,
             cv.Optional(CONF_MAX_QUEUE_AGE, default="8000ms"): cv.All(
                 cv.positive_time_period_milliseconds,
@@ -277,9 +293,6 @@ async def to_code(config):
 
     cg.add(var.set_auto_wake_on_touch(config[CONF_AUTO_WAKE_ON_TOUCH]))
 
-    if config[CONF_DUMP_DEVICE_INFO]:
-        cg.add_define("USE_NEXTION_CONFIG_DUMP_DEVICE_INFO")
-
     if config[CONF_EXIT_REPARSE_ON_START]:
         cg.add_define("USE_NEXTION_CONFIG_EXIT_REPARSE_ON_START")
 

esphome/components/nextion/nextion.cpp

@@ -117,30 +117,41 @@ bool Nextion::check_connect_() {
 
   ESP_LOGN(TAG, "connect: %s", response.c_str());
 
-  size_t start;
+  // Parse comok response fields directly
+  // Format: comok <touch>,<reserved>,<model>,<fw>,<mcu_code>,<serial>,<flash>
+  size_t field_count = 0;
+  size_t start = 0;
   size_t end = 0;
-  std::vector<std::string> connect_info;
+  auto copy_field = [&](char *dst, size_t cap) {
+    size_t len = (end == std::string::npos ? response.size() : end) - start;
+    size_t n = len < cap ? len : cap;
+    std::memcpy(dst, response.data() + start, n);
+    dst[n] = '\0';
+  };
   while ((start = response.find_first_not_of(',', end)) != std::string::npos) {
     end = response.find(',', start);
-    connect_info.push_back(response.substr(start, end - start));
+    switch (field_count) {
+      case 2:
+        copy_field(this->device_model_, this->NEXTION_MODEL_MAX);
+        break;
+      case 3:
+        copy_field(this->firmware_version_, this->NEXTION_FW_MAX);
+        break;
+      case 5:
+        copy_field(this->serial_number_, this->NEXTION_SERIAL_MAX);
+        break;
+      case 6:
+        this->flash_size_ = static_cast<uint32_t>(std::strtoul(response.data() + start, nullptr, 10));
+        break;
+      default:
+        break;
+    }
+    ++field_count;
   }
 
-  this->is_detected_ = (connect_info.size() == 7);
+  this->is_detected_ = (field_count == 7);
   if (this->is_detected_) {
-    ESP_LOGN(TAG, "Connect info: %zu", connect_info.size());
-#ifdef USE_NEXTION_CONFIG_DUMP_DEVICE_INFO
-    this->device_model_ = connect_info[2];
-    this->firmware_version_ = connect_info[3];
-    this->serial_number_ = connect_info[5];
-    this->flash_size_ = connect_info[6];
-#else   // USE_NEXTION_CONFIG_DUMP_DEVICE_INFO
-    ESP_LOGI(TAG,
-             "  Device Model:   %s\n"
-             "  FW Version:     %s\n"
-             "  Serial Number:  %s\n"
-             "  Flash Size:     %s\n",
-             connect_info[2].c_str(), connect_info[3].c_str(), connect_info[5].c_str(), connect_info[6].c_str());
-#endif  // USE_NEXTION_CONFIG_DUMP_DEVICE_INFO
+    ESP_LOGN(TAG, "Connect info: %zu fields", field_count);
   } else {
     ESP_LOGE(TAG, "Bad connect value: '%s'", response.c_str());
   }
@@ -178,24 +189,26 @@ void Nextion::dump_config() {
 #ifdef USE_NEXTION_CONFIG_SKIP_CONNECTION_HANDSHAKE
   ESP_LOGCONFIG(TAG, "  Skip handshake: YES");
 #else  // USE_NEXTION_CONFIG_SKIP_CONNECTION_HANDSHAKE
-#ifdef USE_NEXTION_CONFIG_DUMP_DEVICE_INFO
+  if (this->is_setup()) {
+    ESP_LOGCONFIG(TAG,
+                  "  Device Model: %s\n"
+                  "  FW Version: %s\n"
+                  "  Serial Number: %s\n"
+                  "  Flash Size: %" PRIu32 " bytes",
+                  this->device_model_, this->firmware_version_, this->serial_number_, this->flash_size_);
+  } else {
+    ESP_LOGCONFIG(TAG, "  Device info: not yet detected");
+  }
   ESP_LOGCONFIG(TAG,
-                "  Device Model: %s\n"
-                "  FW Version: %s\n"
-                "  Serial Number: %s\n"
-                "  Flash Size: %s\n"
-                "  Max queue age: %u ms\n"
-                "  Startup override: %u ms\n",
-                this->device_model_.c_str(), this->firmware_version_.c_str(), this->serial_number_.c_str(),
-                this->flash_size_.c_str(), this->max_q_age_ms_, this->startup_override_ms_);
-#endif  // USE_NEXTION_CONFIG_DUMP_DEVICE_INFO
 #ifdef USE_NEXTION_CONFIG_EXIT_REPARSE_ON_START
-  ESP_LOGCONFIG(TAG, "  Exit reparse: YES\n");
+                "  Exit reparse: YES\n"
 #endif  // USE_NEXTION_CONFIG_EXIT_REPARSE_ON_START
-  ESP_LOGCONFIG(TAG,
+                "  Max queue age: %u ms\n"
+                "  Startup override: %u ms\n"
                 "  Wake On Touch: %s\n"
                 "  Touch Timeout: %" PRIu16,
-                YESNO(this->connection_state_.auto_wake_on_touch_), this->touch_sleep_timeout_);
+                this->max_q_age_ms_, this->startup_override_ms_, YESNO(this->connection_state_.auto_wake_on_touch_),
+                this->touch_sleep_timeout_);
 #endif  // USE_NEXTION_CONFIG_SKIP_CONNECTION_HANDSHAKE
 
 #ifdef USE_NEXTION_MAX_COMMANDS_PER_LOOP

esphome/components/nextion/nextion.h

@@ -1610,12 +1610,15 @@ class Nextion : public NextionBase, public PollingComponent, public uart::UARTDe
   nextion_writer_t writer_;
   optional<float> brightness_;
 
-#ifdef USE_NEXTION_CONFIG_DUMP_DEVICE_INFO
-  std::string device_model_;
-  std::string firmware_version_;
-  std::string serial_number_;
-  std::string flash_size_;
-#endif  // USE_NEXTION_CONFIG_DUMP_DEVICE_INFO
+  // Device info populated from comok response (fixed-size, no heap allocation).
+  // Sizes derived from Nextion Upload Protocol documentation and observed hardware.
+  static constexpr size_t NEXTION_MODEL_MAX = 24;   ///< Max observed ~18 chars from product numbering rules
+  static constexpr size_t NEXTION_FW_MAX = 7;       ///< 'S' prefix + integer (e.g. 'S99' or `123`)
+  static constexpr size_t NEXTION_SERIAL_MAX = 20;  ///< Consistently 16 hex chars across all documented examples
+  char device_model_[NEXTION_MODEL_MAX + 1]{};
+  char firmware_version_[NEXTION_FW_MAX + 1]{};
+  char serial_number_[NEXTION_SERIAL_MAX + 1]{};
+  uint32_t flash_size_ = 0;  ///< Flash size in bytes — plain integer, no string needed
 
   void remove_front_no_sensors_();
 

esphome/core/defines.h

@@ -134,7 +134,6 @@
 #define USE_MEDIA_SOURCE
 #define USE_NEXTION_COMMAND_SPACING
 #define USE_NEXTION_CONF_START_UP_PAGE
-#define USE_NEXTION_CONFIG_DUMP_DEVICE_INFO
 #define USE_NEXTION_CONFIG_EXIT_REPARSE_ON_START
 #define USE_NEXTION_CONFIG_SKIP_CONNECTION_HANDSHAKE
 #define USE_NEXTION_MAX_COMMANDS_PER_LOOP

tests/components/nextion/common.yaml

@@ -276,7 +276,6 @@ display:
     auto_wake_on_touch: true
     brightness: 80%
     command_spacing: 5ms
-    dump_device_info: true
     exit_reparse_on_start: true
     lambda: |-
         ESP_LOGD("display","Display is being tested!");