[logger] Conditionally compile log level change listener

esphome/components/logger/__init__.py

@@ -406,6 +406,8 @@ async def to_code(config):
             conf,
         )
 
+    CORE.add_job(final_step)
+
 
 def validate_printf(value):
     # https://stackoverflow.com/questions/30011379/how-can-i-parse-a-c-format-string-in-python
@@ -506,3 +508,23 @@ FILTER_SOURCE_FILES = filter_source_files_from_platform(
         },
     }
 )
+
+# Key for CORE.data to track if level listeners are requested
+LOGGER_LEVEL_LISTENERS_KEY = "logger_level_listeners"
+
+
+def request_logger_level_listeners() -> None:
+    """Request that logger level listeners be compiled in.
+
+    Components that need to be notified about log level changes should call this
+    function during their code generation. This enables the add_level_listener()
+    method and compiles in the listener vector.
+    """
+    CORE.data[LOGGER_LEVEL_LISTENERS_KEY] = True
+
+
+@coroutine_with_priority(CoroPriority.FINAL)
+async def final_step():
+    """Final code generation step to configure optional logger features."""
+    if CORE.data.get(LOGGER_LEVEL_LISTENERS_KEY, False):
+        cg.add_define("USE_LOGGER_LEVEL_LISTENERS")

esphome/components/logger/logger.cpp

@@ -288,7 +288,10 @@ void Logger::set_log_level(uint8_t level) {
     ESP_LOGW(TAG, "Cannot set log level higher than pre-compiled %s", LOG_STR_ARG(LOG_LEVELS[ESPHOME_LOG_LEVEL]));
   }
   this->current_level_ = level;
-  this->level_callback_.call(level);
+#ifdef USE_LOGGER_LEVEL_LISTENERS
+  for (auto *listener : this->level_listeners_)
+    listener->on_log_level_change(level);
+#endif
 }
 
 Logger *global_logger = nullptr;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)

esphome/components/logger/logger.h

@@ -58,6 +58,18 @@ class LogListener {
   virtual void on_log(uint8_t level, const char *tag, const char *message, size_t message_len) = 0;
 };
 
+#ifdef USE_LOGGER_LEVEL_LISTENERS
+/** Interface for receiving log level changes without std::function overhead.
+ *
+ * Components can implement this interface instead of using lambdas with std::function
+ * to reduce flash usage from std::function type erasure machinery.
+ */
+class LoggerLevelListener {
+ public:
+  virtual void on_log_level_change(uint8_t level) = 0;
+};
+#endif
+
 #ifdef USE_LOGGER_RUNTIME_TAG_LEVELS
 // Comparison function for const char* keys in log_levels_ map
 struct CStrCompare {
@@ -193,8 +205,10 @@ class Logger : public Component {
   /// Register a log listener to receive log messages
   void add_log_listener(LogListener *listener) { this->log_listeners_.push_back(listener); }
 
-  // add a listener for log level changes
-  void add_listener(std::function<void(uint8_t)> &&callback) { this->level_callback_.add(std::move(callback)); }
+#ifdef USE_LOGGER_LEVEL_LISTENERS
+  /// Register a listener for log level changes
+  void add_level_listener(LoggerLevelListener *listener) { this->level_listeners_.push_back(listener); }
+#endif
 
   float get_setup_priority() const override;
 
@@ -325,7 +339,9 @@ class Logger : public Component {
   std::map<const char *, uint8_t, CStrCompare> log_levels_{};
 #endif
   std::vector<LogListener *> log_listeners_;  // Log message listeners (API, MQTT, syslog, etc.)
-  CallbackManager<void(uint8_t)> level_callback_{};
+#ifdef USE_LOGGER_LEVEL_LISTENERS
+  std::vector<LoggerLevelListener *> level_listeners_;  // Log level change listeners
+#endif
 #ifdef USE_ESPHOME_TASK_LOG_BUFFER
   std::unique_ptr<logger::TaskLogBuffer> log_buffer_;  // Will be initialized with init_log_buffer
 #endif

esphome/components/logger/select/__init__.py

@@ -5,7 +5,13 @@ from esphome.const import CONF_LEVEL, CONF_LOGGER, ENTITY_CATEGORY_CONFIG, ICON_
 from esphome.core import CORE
 from esphome.cpp_helpers import register_component, register_parented
 
-from .. import CONF_LOGGER_ID, LOG_LEVELS, Logger, logger_ns
+from .. import (
+    CONF_LOGGER_ID,
+    LOG_LEVELS,
+    Logger,
+    logger_ns,
+    request_logger_level_listeners,
+)
 
 CODEOWNERS = ["@clydebarrow"]
 
@@ -21,6 +27,7 @@ CONFIG_SCHEMA = select.select_schema(
 
 
 async def to_code(config):
+    request_logger_level_listeners()
     parent = await cg.get_variable(config[CONF_LOGGER_ID])
     levels = list(LOG_LEVELS)
     index = levels.index(CORE.data[CONF_LOGGER][CONF_LEVEL])

esphome/components/logger/select/logger_level_select.cpp

@@ -2,7 +2,7 @@
 
 namespace esphome::logger {
 
-void LoggerLevelSelect::publish_state(int level) {
+void LoggerLevelSelect::on_log_level_change(uint8_t level) {
   auto index = level_to_index(level);
   if (!this->has_index(index))
     return;
@@ -10,8 +10,8 @@ void LoggerLevelSelect::publish_state(int level) {
 }
 
 void LoggerLevelSelect::setup() {
-  this->parent_->add_listener([this](int level) { this->publish_state(level); });
-  this->publish_state(this->parent_->get_log_level());
+  this->parent_->add_level_listener(this);
+  this->on_log_level_change(this->parent_->get_log_level());
 }
 
 void LoggerLevelSelect::control(size_t index) { this->parent_->set_log_level(index_to_level(index)); }

esphome/components/logger/select/logger_level_select.h

@@ -5,12 +5,17 @@
 #include "esphome/components/logger/logger.h"
 
 namespace esphome::logger {
-class LoggerLevelSelect : public Component, public select::Select, public Parented<Logger> {
+class LoggerLevelSelect final : public Component,
+                                public select::Select,
+                                public Parented<Logger>,
+                                public LoggerLevelListener {
  public:
-  void publish_state(int level);
   void setup() override;
   void control(size_t index) override;
 
+  // LoggerLevelListener interface
+  void on_log_level_change(uint8_t level) override;
+
  protected:
   // Convert log level to option index (skip CONFIG at level 4)
   static uint8_t level_to_index(uint8_t level) { return (level > ESPHOME_LOG_LEVEL_CONFIG) ? level - 1 : level; }

esphome/core/defines.h

@@ -51,6 +51,7 @@
 #define USE_LIGHT
 #define USE_LOCK
 #define USE_LOGGER
+#define USE_LOGGER_LEVEL_LISTENERS
 #define USE_LOGGER_RUNTIME_TAG_LEVELS
 #define USE_LVGL
 #define USE_LVGL_ANIMIMG