[fan] Make get_preset_mode() return empty string instead of nullptr for safety

esphome/components/copy/fan/copy_fan.cpp

@@ -8,20 +8,24 @@ static const char *const TAG = "copy.fan";
 
 void CopyFan::setup() {
   source_->add_on_state_callback([this]() {
-    this->state = source_->state;
-    this->oscillating = source_->oscillating;
-    this->speed = source_->speed;
-    this->direction = source_->direction;
-    this->set_preset_mode_(source_->get_preset_mode());
+    this->copy_state_from_source_();
     this->publish_state();
   });
 
+  this->copy_state_from_source_();
+  this->publish_state();
+}
+
+void CopyFan::copy_state_from_source_() {
   this->state = source_->state;
   this->oscillating = source_->oscillating;
   this->speed = source_->speed;
   this->direction = source_->direction;
-  this->set_preset_mode_(source_->get_preset_mode());
-  this->publish_state();
+  if (source_->has_preset_mode()) {
+    this->set_preset_mode_(source_->get_preset_mode());
+  } else {
+    this->clear_preset_mode_();
+  }
 }
 
 void CopyFan::dump_config() { LOG_FAN("", "Copy Fan", this); }

esphome/components/copy/fan/copy_fan.h

@@ -16,7 +16,7 @@ class CopyFan : public fan::Fan, public Component {
 
  protected:
   void control(const fan::FanCall &call) override;
-  ;
+  void copy_state_from_source_();
 
   fan::Fan *source_;
 };

esphome/components/fan/automation.h

@@ -216,15 +216,14 @@ class FanPresetSetTrigger : public Trigger<std::string> {
       auto should_trigger = preset_mode != this->last_preset_mode_;
       this->last_preset_mode_ = preset_mode;
       if (should_trigger) {
-        // Trigger with empty string when nullptr to maintain backward compatibility
-        this->trigger(preset_mode != nullptr ? preset_mode : "");
+        this->trigger(preset_mode);
       }
     });
     this->last_preset_mode_ = state->get_preset_mode();
   }
 
  protected:
-  const char *last_preset_mode_{nullptr};
+  const char *last_preset_mode_{""};
 };
 
 }  // namespace fan

esphome/components/fan/fan.cpp

@@ -83,7 +83,7 @@ void FanCall::validate_() {
       *this->binary_state_
       // ..,and no preset mode will be active...
       && !this->has_preset_mode() &&
-      this->parent_.get_preset_mode() == nullptr
+      !this->parent_.has_preset_mode()
       // ...and neither current nor new speed is available...
       && traits.supports_speed() && this->parent_.speed == 0 && !this->speed_.has_value()) {
     // ...set speed to 100%
@@ -175,6 +175,15 @@ bool Fan::set_preset_mode_(const std::string &preset_mode) { return this->set_pr
 
 void Fan::clear_preset_mode_() { this->preset_mode_ = nullptr; }
 
+void Fan::apply_preset_mode_(const FanCall &call) {
+  if (call.has_preset_mode()) {
+    this->set_preset_mode_(call.get_preset_mode());
+  } else if (call.get_speed().has_value()) {
+    // Manually setting speed clears preset (per Home Assistant convention)
+    this->clear_preset_mode_();
+  }
+}
+
 void Fan::add_on_state_callback(std::function<void()> &&callback) { this->state_callback_.add(std::move(callback)); }
 void Fan::publish_state() {
   auto traits = this->get_traits();
@@ -192,9 +201,8 @@ void Fan::publish_state() {
   if (traits.supports_direction()) {
     ESP_LOGD(TAG, "  Direction: %s", LOG_STR_ARG(fan_direction_to_string(this->direction)));
   }
-  const char *preset = this->get_preset_mode();
-  if (preset != nullptr) {
-    ESP_LOGD(TAG, "  Preset Mode: %s", preset);
+  if (this->has_preset_mode()) {
+    ESP_LOGD(TAG, "  Preset Mode: %s", this->get_preset_mode());
   }
   this->state_callback_.call();
 #if defined(USE_FAN) && defined(USE_CONTROLLER_REGISTRY)
@@ -249,12 +257,11 @@ void Fan::save_state_() {
   state.speed = this->speed;
   state.direction = this->direction;
 
-  const char *preset = this->get_preset_mode();
-  if (preset != nullptr) {
+  if (this->has_preset_mode()) {
     const auto &preset_modes = traits.supported_preset_modes();
     // Find index of current preset mode (pointer comparison is safe since preset is from traits)
     for (size_t i = 0; i < preset_modes.size(); i++) {
-      if (preset_modes[i] == preset) {
+      if (preset_modes[i] == this->preset_mode_) {
         state.preset_mode = i;
         break;
       }

esphome/components/fan/fan.h

@@ -128,8 +128,8 @@ class Fan : public EntityBase {
   /// Set the restore mode of this fan.
   void set_restore_mode(FanRestoreMode restore_mode) { this->restore_mode_ = restore_mode; }
 
-  /// Get the current preset mode (returns pointer to string stored in traits, or nullptr if not set)
-  const char *get_preset_mode() const { return this->preset_mode_; }
+  /// Get the current preset mode (returns pointer to string stored in traits, or empty string if not set)
+  const char *get_preset_mode() const { return this->preset_mode_ != nullptr ? this->preset_mode_ : ""; }
 
   /// Check if a preset mode is currently active
   bool has_preset_mode() const { return this->preset_mode_ != nullptr; }
@@ -151,6 +151,8 @@ class Fan : public EntityBase {
   bool set_preset_mode_(const std::string &preset_mode);
   /// Clear the preset mode
   void clear_preset_mode_();
+  /// Apply preset mode from a FanCall (handles speed-clears-preset convention)
+  void apply_preset_mode_(const FanCall &call);
   /// Find and return the matching preset mode pointer from traits, or nullptr if not found.
   const char *find_preset_mode_(const char *preset_mode);
   const char *find_preset_mode_(const char *preset_mode, size_t len);

esphome/components/hbridge/fan/hbridge_fan.cpp

@@ -57,7 +57,7 @@ void HBridgeFan::control(const fan::FanCall &call) {
     this->oscillating = *call.get_oscillating();
   if (call.get_direction().has_value())
     this->direction = *call.get_direction();
-  this->set_preset_mode_(call.get_preset_mode());
+  this->apply_preset_mode_(call);
 
   this->write_state_();
   this->publish_state();

esphome/components/speed/fan/speed_fan.cpp

@@ -29,7 +29,7 @@ void SpeedFan::control(const fan::FanCall &call) {
     this->oscillating = *call.get_oscillating();
   if (call.get_direction().has_value())
     this->direction = *call.get_direction();
-  this->set_preset_mode_(call.get_preset_mode());
+  this->apply_preset_mode_(call);
 
   this->write_state_();
   this->publish_state();

esphome/components/template/fan/template_fan.cpp

@@ -28,7 +28,7 @@ void TemplateFan::control(const fan::FanCall &call) {
     this->oscillating = *call.get_oscillating();
   if (call.get_direction().has_value() && this->has_direction_)
     this->direction = *call.get_direction();
-  this->set_preset_mode_(call.get_preset_mode());
+  this->apply_preset_mode_(call);
 
   this->publish_state();
 }