[template] Eliminate optional wrapper to save 4 bytes RAM per instance (#11610)

esphome/components/template/binary_sensor/template_binary_sensor.cpp

@@ -6,17 +6,21 @@ namespace template_ {
 
 static const char *const TAG = "template.binary_sensor";
 
-void TemplateBinarySensor::setup() { this->loop(); }
+void TemplateBinarySensor::setup() {
+  if (!this->f_.has_value()) {
+    this->disable_loop();
+  } else {
+    this->loop();
+  }
+}
 
 void TemplateBinarySensor::loop() {
-  if (!this->f_.has_value())
-    return;
-
-  auto s = (*this->f_)();
+  auto s = this->f_();
   if (s.has_value()) {
     this->publish_state(*s);
   }
 }
+
 void TemplateBinarySensor::dump_config() { LOG_BINARY_SENSOR("", "Template Binary Sensor", this); }
 
 }  // namespace template_

esphome/components/template/binary_sensor/template_binary_sensor.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "esphome/core/component.h"
+#include "esphome/core/template_lambda.h"
 #include "esphome/components/binary_sensor/binary_sensor.h"
 
 namespace esphome {
@@ -8,7 +9,7 @@ namespace template_ {
 
 class TemplateBinarySensor : public Component, public binary_sensor::BinarySensor {
  public:
-  void set_template(optional<bool> (*f)()) { this->f_ = f; }
+  template<typename F> void set_template(F &&f) { this->f_.set(std::forward<F>(f)); }
 
   void setup() override;
   void loop() override;
@@ -17,7 +18,7 @@ class TemplateBinarySensor : public Component, public binary_sensor::BinarySenso
   float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
  protected:
-  optional<optional<bool> (*)()> f_;
+  TemplateLambda<bool> f_;
 };
 
 }  // namespace template_

esphome/components/template/cover/template_cover.cpp

@@ -33,28 +33,27 @@ void TemplateCover::setup() {
       break;
     }
   }
+  if (!this->state_f_.has_value() && !this->tilt_f_.has_value())
+    this->disable_loop();
 }
 void TemplateCover::loop() {
   bool changed = false;
 
-  if (this->state_f_.has_value()) {
-    auto s = (*this->state_f_)();
-    if (s.has_value()) {
-      auto pos = clamp(*s, 0.0f, 1.0f);
-      if (pos != this->position) {
-        this->position = pos;
-        changed = true;
-      }
+  auto s = this->state_f_();
+  if (s.has_value()) {
+    auto pos = clamp(*s, 0.0f, 1.0f);
+    if (pos != this->position) {
+      this->position = pos;
+      changed = true;
     }
   }
-  if (this->tilt_f_.has_value()) {
-    auto s = (*this->tilt_f_)();
-    if (s.has_value()) {
-      auto tilt = clamp(*s, 0.0f, 1.0f);
-      if (tilt != this->tilt) {
-        this->tilt = tilt;
-        changed = true;
-      }
+
+  auto tilt = this->tilt_f_();
+  if (tilt.has_value()) {
+    auto tilt_val = clamp(*tilt, 0.0f, 1.0f);
+    if (tilt_val != this->tilt) {
+      this->tilt = tilt_val;
+      changed = true;
     }
   }
 
@@ -63,7 +62,6 @@ void TemplateCover::loop() {
 }
 void TemplateCover::set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
 void TemplateCover::set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
-void TemplateCover::set_state_lambda(optional<float> (*f)()) { this->state_f_ = f; }
 float TemplateCover::get_setup_priority() const { return setup_priority::HARDWARE; }
 Trigger<> *TemplateCover::get_open_trigger() const { return this->open_trigger_; }
 Trigger<> *TemplateCover::get_close_trigger() const { return this->close_trigger_; }
@@ -124,7 +122,6 @@ CoverTraits TemplateCover::get_traits() {
 }
 Trigger<float> *TemplateCover::get_position_trigger() const { return this->position_trigger_; }
 Trigger<float> *TemplateCover::get_tilt_trigger() const { return this->tilt_trigger_; }
-void TemplateCover::set_tilt_lambda(optional<float> (*tilt_f)()) { this->tilt_f_ = tilt_f; }
 void TemplateCover::set_has_stop(bool has_stop) { this->has_stop_ = has_stop; }
 void TemplateCover::set_has_toggle(bool has_toggle) { this->has_toggle_ = has_toggle; }
 void TemplateCover::set_has_position(bool has_position) { this->has_position_ = has_position; }

esphome/components/template/cover/template_cover.h

@@ -2,6 +2,7 @@
 
 #include "esphome/core/component.h"
 #include "esphome/core/automation.h"
+#include "esphome/core/template_lambda.h"
 #include "esphome/components/cover/cover.h"
 
 namespace esphome {
@@ -17,7 +18,8 @@ class TemplateCover : public cover::Cover, public Component {
  public:
   TemplateCover();
 
-  void set_state_lambda(optional<float> (*f)());
+  template<typename F> void set_state_lambda(F &&f) { this->state_f_.set(std::forward<F>(f)); }
+  template<typename F> void set_tilt_lambda(F &&f) { this->tilt_f_.set(std::forward<F>(f)); }
   Trigger<> *get_open_trigger() const;
   Trigger<> *get_close_trigger() const;
   Trigger<> *get_stop_trigger() const;
@@ -26,7 +28,6 @@ class TemplateCover : public cover::Cover, public Component {
   Trigger<float> *get_tilt_trigger() const;
   void set_optimistic(bool optimistic);
   void set_assumed_state(bool assumed_state);
-  void set_tilt_lambda(optional<float> (*tilt_f)());
   void set_has_stop(bool has_stop);
   void set_has_position(bool has_position);
   void set_has_tilt(bool has_tilt);
@@ -45,8 +46,8 @@ class TemplateCover : public cover::Cover, public Component {
   void stop_prev_trigger_();
 
   TemplateCoverRestoreMode restore_mode_{COVER_RESTORE};
-  optional<optional<float> (*)()> state_f_;
-  optional<optional<float> (*)()> tilt_f_;
+  TemplateLambda<float> state_f_;
+  TemplateLambda<float> tilt_f_;
   bool assumed_state_{false};
   bool optimistic_{false};
   Trigger<> *open_trigger_;

esphome/components/template/datetime/template_date.cpp

@@ -40,14 +40,13 @@ void TemplateDate::update() {
   if (!this->f_.has_value())
     return;
 
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
-
-  this->year_ = val->year;
-  this->month_ = val->month;
-  this->day_ = val->day_of_month;
-  this->publish_state();
+  auto val = this->f_();
+  if (val.has_value()) {
+    this->year_ = val->year;
+    this->month_ = val->month;
+    this->day_ = val->day_of_month;
+    this->publish_state();
+  }
 }
 
 void TemplateDate::control(const datetime::DateCall &call) {

esphome/components/template/datetime/template_date.h

@@ -9,13 +9,14 @@
 #include "esphome/core/component.h"
 #include "esphome/core/preferences.h"
 #include "esphome/core/time.h"
+#include "esphome/core/template_lambda.h"
 
 namespace esphome {
 namespace template_ {
 
 class TemplateDate : public datetime::DateEntity, public PollingComponent {
  public:
-  void set_template(optional<ESPTime> (*f)()) { this->f_ = f; }
+  template<typename F> void set_template(F &&f) { this->f_.set(std::forward<F>(f)); }
 
   void setup() override;
   void update() override;
@@ -35,7 +36,7 @@ class TemplateDate : public datetime::DateEntity, public PollingComponent {
   ESPTime initial_value_{};
   bool restore_value_{false};
   Trigger<ESPTime> *set_trigger_ = new Trigger<ESPTime>();
-  optional<optional<ESPTime> (*)()> f_;
+  TemplateLambda<ESPTime> f_;
 
   ESPPreferenceObject pref_;
 };

esphome/components/template/datetime/template_datetime.cpp

@@ -43,17 +43,16 @@ void TemplateDateTime::update() {
   if (!this->f_.has_value())
     return;
 
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
-
-  this->year_ = val->year;
-  this->month_ = val->month;
-  this->day_ = val->day_of_month;
-  this->hour_ = val->hour;
-  this->minute_ = val->minute;
-  this->second_ = val->second;
-  this->publish_state();
+  auto val = this->f_();
+  if (val.has_value()) {
+    this->year_ = val->year;
+    this->month_ = val->month;
+    this->day_ = val->day_of_month;
+    this->hour_ = val->hour;
+    this->minute_ = val->minute;
+    this->second_ = val->second;
+    this->publish_state();
+  }
 }
 
 void TemplateDateTime::control(const datetime::DateTimeCall &call) {

esphome/components/template/datetime/template_datetime.h

@@ -9,13 +9,14 @@
 #include "esphome/core/component.h"
 #include "esphome/core/preferences.h"
 #include "esphome/core/time.h"
+#include "esphome/core/template_lambda.h"
 
 namespace esphome {
 namespace template_ {
 
 class TemplateDateTime : public datetime::DateTimeEntity, public PollingComponent {
  public:
-  void set_template(optional<ESPTime> (*f)()) { this->f_ = f; }
+  template<typename F> void set_template(F &&f) { this->f_.set(std::forward<F>(f)); }
 
   void setup() override;
   void update() override;
@@ -35,7 +36,7 @@ class TemplateDateTime : public datetime::DateTimeEntity, public PollingComponen
   ESPTime initial_value_{};
   bool restore_value_{false};
   Trigger<ESPTime> *set_trigger_ = new Trigger<ESPTime>();
-  optional<optional<ESPTime> (*)()> f_;
+  TemplateLambda<ESPTime> f_;
 
   ESPPreferenceObject pref_;
 };

esphome/components/template/datetime/template_time.cpp

@@ -40,14 +40,13 @@ void TemplateTime::update() {
   if (!this->f_.has_value())
     return;
 
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
-
-  this->hour_ = val->hour;
-  this->minute_ = val->minute;
-  this->second_ = val->second;
-  this->publish_state();
+  auto val = this->f_();
+  if (val.has_value()) {
+    this->hour_ = val->hour;
+    this->minute_ = val->minute;
+    this->second_ = val->second;
+    this->publish_state();
+  }
 }
 
 void TemplateTime::control(const datetime::TimeCall &call) {

esphome/components/template/datetime/template_time.h

@@ -9,13 +9,14 @@
 #include "esphome/core/component.h"
 #include "esphome/core/preferences.h"
 #include "esphome/core/time.h"
+#include "esphome/core/template_lambda.h"
 
 namespace esphome {
 namespace template_ {
 
 class TemplateTime : public datetime::TimeEntity, public PollingComponent {
  public:
-  void set_template(optional<ESPTime> (*f)()) { this->f_ = f; }
+  template<typename F> void set_template(F &&f) { this->f_.set(std::forward<F>(f)); }
 
   void setup() override;
   void update() override;
@@ -35,7 +36,7 @@ class TemplateTime : public datetime::TimeEntity, public PollingComponent {
   ESPTime initial_value_{};
   bool restore_value_{false};
   Trigger<ESPTime> *set_trigger_ = new Trigger<ESPTime>();
-  optional<optional<ESPTime> (*)()> f_;
+  TemplateLambda<ESPTime> f_;
 
   ESPPreferenceObject pref_;
 };

esphome/components/template/lock/template_lock.cpp

@@ -11,14 +11,16 @@ static const char *const TAG = "template.lock";
 TemplateLock::TemplateLock()
     : lock_trigger_(new Trigger<>()), unlock_trigger_(new Trigger<>()), open_trigger_(new Trigger<>()) {}
 
-void TemplateLock::loop() {
+void TemplateLock::setup() {
   if (!this->f_.has_value())
-    return;
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
+    this->disable_loop();
+}
 
-  this->publish_state(*val);
+void TemplateLock::loop() {
+  auto val = this->f_();
+  if (val.has_value()) {
+    this->publish_state(*val);
+  }
 }
 void TemplateLock::control(const lock::LockCall &call) {
   if (this->prev_trigger_ != nullptr) {
@@ -45,7 +47,6 @@ void TemplateLock::open_latch() {
   this->open_trigger_->trigger();
 }
 void TemplateLock::set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
-void TemplateLock::set_state_lambda(optional<lock::LockState> (*f)()) { this->f_ = f; }
 float TemplateLock::get_setup_priority() const { return setup_priority::HARDWARE; }
 Trigger<> *TemplateLock::get_lock_trigger() const { return this->lock_trigger_; }
 Trigger<> *TemplateLock::get_unlock_trigger() const { return this->unlock_trigger_; }

esphome/components/template/lock/template_lock.h

@@ -2,6 +2,7 @@
 
 #include "esphome/core/component.h"
 #include "esphome/core/automation.h"
+#include "esphome/core/template_lambda.h"
 #include "esphome/components/lock/lock.h"
 
 namespace esphome {
@@ -11,9 +12,10 @@ class TemplateLock : public lock::Lock, public Component {
  public:
   TemplateLock();
 
+  void setup() override;
   void dump_config() override;
 
-  void set_state_lambda(optional<lock::LockState> (*f)());
+  template<typename F> void set_state_lambda(F &&f) { this->f_.set(std::forward<F>(f)); }
   Trigger<> *get_lock_trigger() const;
   Trigger<> *get_unlock_trigger() const;
   Trigger<> *get_open_trigger() const;
@@ -26,7 +28,7 @@ class TemplateLock : public lock::Lock, public Component {
   void control(const lock::LockCall &call) override;
   void open_latch() override;
 
-  optional<optional<lock::LockState> (*)()> f_;
+  TemplateLambda<lock::LockState> f_;
   bool optimistic_{false};
   Trigger<> *lock_trigger_;
   Trigger<> *unlock_trigger_;

esphome/components/template/number/template_number.cpp

@@ -30,11 +30,10 @@ void TemplateNumber::update() {
   if (!this->f_.has_value())
     return;
 
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
-
-  this->publish_state(*val);
+  auto val = this->f_();
+  if (val.has_value()) {
+    this->publish_state(*val);
+  }
 }
 
 void TemplateNumber::control(float value) {

esphome/components/template/number/template_number.h

@@ -4,13 +4,14 @@
 #include "esphome/core/automation.h"
 #include "esphome/core/component.h"
 #include "esphome/core/preferences.h"
+#include "esphome/core/template_lambda.h"
 
 namespace esphome {
 namespace template_ {
 
 class TemplateNumber : public number::Number, public PollingComponent {
  public:
-  void set_template(optional<float> (*f)()) { this->f_ = f; }
+  template<typename F> void set_template(F &&f) { this->f_.set(std::forward<F>(f)); }
 
   void setup() override;
   void update() override;
@@ -28,7 +29,7 @@ class TemplateNumber : public number::Number, public PollingComponent {
   float initial_value_{NAN};
   bool restore_value_{false};
   Trigger<float> *set_trigger_ = new Trigger<float>();
-  optional<optional<float> (*)()> f_;
+  TemplateLambda<float> f_;
 
   ESPPreferenceObject pref_;
 };

esphome/components/template/select/template_select.cpp

@@ -31,16 +31,14 @@ void TemplateSelect::update() {
   if (!this->f_.has_value())
     return;
 
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
-
-  if (!this->has_option(*val)) {
-    ESP_LOGE(TAG, "Lambda returned an invalid option: %s", (*val).c_str());
-    return;
+  auto val = this->f_();
+  if (val.has_value()) {
+    if (!this->has_option(*val)) {
+      ESP_LOGE(TAG, "Lambda returned an invalid option: %s", (*val).c_str());
+      return;
+    }
+    this->publish_state(*val);
   }
-
-  this->publish_state(*val);
 }
 
 void TemplateSelect::control(const std::string &value) {

esphome/components/template/select/template_select.h

@@ -4,13 +4,14 @@
 #include "esphome/core/automation.h"
 #include "esphome/core/component.h"
 #include "esphome/core/preferences.h"
+#include "esphome/core/template_lambda.h"
 
 namespace esphome {
 namespace template_ {
 
 class TemplateSelect : public select::Select, public PollingComponent {
  public:
-  void set_template(optional<std::string> (*f)()) { this->f_ = f; }
+  template<typename F> void set_template(F &&f) { this->f_.set(std::forward<F>(f)); }
 
   void setup() override;
   void update() override;
@@ -28,7 +29,7 @@ class TemplateSelect : public select::Select, public PollingComponent {
   size_t initial_option_index_{0};
   bool restore_value_ = false;
   Trigger<std::string> *set_trigger_ = new Trigger<std::string>();
-  optional<optional<std::string> (*)()> f_;
+  TemplateLambda<std::string> f_;
 
   ESPPreferenceObject pref_;
 };

esphome/components/template/sensor/template_sensor.cpp

@@ -11,13 +11,14 @@ void TemplateSensor::update() {
   if (!this->f_.has_value())
     return;
 
-  auto val = (*this->f_)();
+  auto val = this->f_();
   if (val.has_value()) {
     this->publish_state(*val);
   }
 }
+
 float TemplateSensor::get_setup_priority() const { return setup_priority::HARDWARE; }
-void TemplateSensor::set_template(optional<float> (*f)()) { this->f_ = f; }
+
 void TemplateSensor::dump_config() {
   LOG_SENSOR("", "Template Sensor", this);
   LOG_UPDATE_INTERVAL(this);

esphome/components/template/sensor/template_sensor.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "esphome/core/component.h"
+#include "esphome/core/template_lambda.h"
 #include "esphome/components/sensor/sensor.h"
 
 namespace esphome {
@@ -8,7 +9,7 @@ namespace template_ {
 
 class TemplateSensor : public sensor::Sensor, public PollingComponent {
  public:
-  void set_template(optional<float> (*f)());
+  template<typename F> void set_template(F &&f) { this->f_.set(std::forward<F>(f)); }
 
   void update() override;
 
@@ -17,7 +18,7 @@ class TemplateSensor : public sensor::Sensor, public PollingComponent {
   float get_setup_priority() const override;
 
  protected:
-  optional<optional<float> (*)()> f_;
+  TemplateLambda<float> f_;
 };
 
 }  // namespace template_

esphome/components/template/switch/template_switch.cpp

@@ -9,13 +9,10 @@ static const char *const TAG = "template.switch";
 TemplateSwitch::TemplateSwitch() : turn_on_trigger_(new Trigger<>()), turn_off_trigger_(new Trigger<>()) {}
 
 void TemplateSwitch::loop() {
-  if (!this->f_.has_value())
-    return;
-  auto s = (*this->f_)();
-  if (!s.has_value())
-    return;
-
-  this->publish_state(*s);
+  auto s = this->f_();
+  if (s.has_value()) {
+    this->publish_state(*s);
+  }
 }
 void TemplateSwitch::write_state(bool state) {
   if (this->prev_trigger_ != nullptr) {
@@ -35,11 +32,13 @@ void TemplateSwitch::write_state(bool state) {
 }
 void TemplateSwitch::set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
 bool TemplateSwitch::assumed_state() { return this->assumed_state_; }
-void TemplateSwitch::set_state_lambda(optional<bool> (*f)()) { this->f_ = f; }
 float TemplateSwitch::get_setup_priority() const { return setup_priority::HARDWARE - 2.0f; }
 Trigger<> *TemplateSwitch::get_turn_on_trigger() const { return this->turn_on_trigger_; }
 Trigger<> *TemplateSwitch::get_turn_off_trigger() const { return this->turn_off_trigger_; }
 void TemplateSwitch::setup() {
+  if (!this->f_.has_value())
+    this->disable_loop();
+
   optional<bool> initial_state = this->get_initial_state_with_restore_mode();
 
   if (initial_state.has_value()) {

esphome/components/template/switch/template_switch.h

@@ -2,6 +2,7 @@
 
 #include "esphome/core/component.h"
 #include "esphome/core/automation.h"
+#include "esphome/core/template_lambda.h"
 #include "esphome/components/switch/switch.h"
 
 namespace esphome {
@@ -14,7 +15,7 @@ class TemplateSwitch : public switch_::Switch, public Component {
   void setup() override;
   void dump_config() override;
 
-  void set_state_lambda(optional<bool> (*f)());
+  template<typename F> void set_state_lambda(F &&f) { this->f_.set(std::forward<F>(f)); }
   Trigger<> *get_turn_on_trigger() const;
   Trigger<> *get_turn_off_trigger() const;
   void set_optimistic(bool optimistic);
@@ -28,7 +29,7 @@ class TemplateSwitch : public switch_::Switch, public Component {
 
   void write_state(bool state) override;
 
-  optional<optional<bool> (*)()> f_;
+  TemplateLambda<bool> f_;
   bool optimistic_{false};
   bool assumed_state_{false};
   Trigger<> *turn_on_trigger_;

esphome/components/template/text/template_text.cpp

@@ -7,10 +7,8 @@ namespace template_ {
 static const char *const TAG = "template.text";
 
 void TemplateText::setup() {
-  if (!(this->f_ == nullptr)) {
-    if (this->f_.has_value())
-      return;
-  }
+  if (this->f_.has_value())
+    return;
   std::string value = this->initial_value_;
   if (!this->pref_) {
     ESP_LOGD(TAG, "State from initial: %s", value.c_str());
@@ -26,17 +24,13 @@ void TemplateText::setup() {
 }
 
 void TemplateText::update() {
-  if (this->f_ == nullptr)
-    return;
-
   if (!this->f_.has_value())
     return;
 
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
-
-  this->publish_state(*val);
+  auto val = this->f_();
+  if (val.has_value()) {
+    this->publish_state(*val);
+  }
 }
 
 void TemplateText::control(const std::string &value) {

esphome/components/template/text/template_text.h

@@ -4,6 +4,7 @@
 #include "esphome/core/automation.h"
 #include "esphome/core/component.h"
 #include "esphome/core/preferences.h"
+#include "esphome/core/template_lambda.h"
 
 namespace esphome {
 namespace template_ {
@@ -61,7 +62,7 @@ template<uint8_t SZ> class TextSaver : public TemplateTextSaverBase {
 
 class TemplateText : public text::Text, public PollingComponent {
  public:
-  void set_template(optional<std::string> (*f)()) { this->f_ = f; }
+  template<typename F> void set_template(F &&f) { this->f_.set(std::forward<F>(f)); }
 
   void setup() override;
   void update() override;
@@ -78,7 +79,7 @@ class TemplateText : public text::Text, public PollingComponent {
   bool optimistic_ = false;
   std::string initial_value_;
   Trigger<std::string> *set_trigger_ = new Trigger<std::string>();
-  optional<optional<std::string> (*)()> f_{nullptr};
+  TemplateLambda<std::string> f_{};
 
   TemplateTextSaverBase *pref_ = nullptr;
 };

esphome/components/template/text_sensor/template_text_sensor.cpp

@@ -10,13 +10,14 @@ void TemplateTextSensor::update() {
   if (!this->f_.has_value())
     return;
 
-  auto val = (*this->f_)();
+  auto val = this->f_();
   if (val.has_value()) {
     this->publish_state(*val);
   }
 }
+
 float TemplateTextSensor::get_setup_priority() const { return setup_priority::HARDWARE; }
-void TemplateTextSensor::set_template(optional<std::string> (*f)()) { this->f_ = f; }
+
 void TemplateTextSensor::dump_config() { LOG_TEXT_SENSOR("", "Template Sensor", this); }
 
 }  // namespace template_

esphome/components/template/text_sensor/template_text_sensor.h

@@ -2,6 +2,7 @@
 
 #include "esphome/core/component.h"
 #include "esphome/core/automation.h"
+#include "esphome/core/template_lambda.h"
 #include "esphome/components/text_sensor/text_sensor.h"
 
 namespace esphome {
@@ -9,7 +10,7 @@ namespace template_ {
 
 class TemplateTextSensor : public text_sensor::TextSensor, public PollingComponent {
  public:
-  void set_template(optional<std::string> (*f)());
+  template<typename F> void set_template(F &&f) { this->f_.set(std::forward<F>(f)); }
 
   void update() override;
 
@@ -18,7 +19,7 @@ class TemplateTextSensor : public text_sensor::TextSensor, public PollingCompone
   void dump_config() override;
 
  protected:
-  optional<optional<std::string> (*)()> f_{};
+  TemplateLambda<std::string> f_{};
 };
 
 }  // namespace template_

esphome/components/template/valve/template_valve.cpp

@@ -33,19 +33,19 @@ void TemplateValve::setup() {
       break;
     }
   }
+  if (!this->state_f_.has_value())
+    this->disable_loop();
 }
 
 void TemplateValve::loop() {
   bool changed = false;
 
-  if (this->state_f_.has_value()) {
-    auto s = (*this->state_f_)();
-    if (s.has_value()) {
-      auto pos = clamp(*s, 0.0f, 1.0f);
-      if (pos != this->position) {
-        this->position = pos;
-        changed = true;
-      }
+  auto s = this->state_f_();
+  if (s.has_value()) {
+    auto pos = clamp(*s, 0.0f, 1.0f);
+    if (pos != this->position) {
+      this->position = pos;
+      changed = true;
     }
   }
 
@@ -55,7 +55,6 @@ void TemplateValve::loop() {
 
 void TemplateValve::set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
 void TemplateValve::set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
-void TemplateValve::set_state_lambda(optional<float> (*f)()) { this->state_f_ = f; }
 float TemplateValve::get_setup_priority() const { return setup_priority::HARDWARE; }
 
 Trigger<> *TemplateValve::get_open_trigger() const { return this->open_trigger_; }

esphome/components/template/valve/template_valve.h

@@ -2,6 +2,7 @@
 
 #include "esphome/core/component.h"
 #include "esphome/core/automation.h"
+#include "esphome/core/template_lambda.h"
 #include "esphome/components/valve/valve.h"
 
 namespace esphome {
@@ -17,7 +18,7 @@ class TemplateValve : public valve::Valve, public Component {
  public:
   TemplateValve();
 
-  void set_state_lambda(optional<float> (*f)());
+  template<typename F> void set_state_lambda(F &&f) { this->state_f_.set(std::forward<F>(f)); }
   Trigger<> *get_open_trigger() const;
   Trigger<> *get_close_trigger() const;
   Trigger<> *get_stop_trigger() const;
@@ -42,7 +43,7 @@ class TemplateValve : public valve::Valve, public Component {
   void stop_prev_trigger_();
 
   TemplateValveRestoreMode restore_mode_{VALVE_NO_RESTORE};
-  optional<optional<float> (*)()> state_f_;
+  TemplateLambda<float> state_f_;
   bool assumed_state_{false};
   bool optimistic_{false};
   Trigger<> *open_trigger_;

esphome/core/template_lambda.h

@@ -0,0 +1,51 @@
+#pragma once
+
+#include "esphome/core/optional.h"
+
+namespace esphome {
+
+/** Lightweight wrapper for template platform lambdas (stateless function pointers only).
+ *
+ * This optimizes template platforms by storing only a function pointer (4 bytes on ESP32)
+ * instead of std::function (16-32 bytes).
+ *
+ * IMPORTANT: This only supports stateless lambdas (no captures). The set_template() method
+ * is an internal API used by YAML codegen, not intended for external use.
+ *
+ * Lambdas must return optional<T> to support the pattern:
+ *   return {};    // Don't publish a value
+ *   return 42.0;  // Publish this value
+ *
+ * operator() returns optional<T>, returning nullopt when no lambda is set (nullptr check).
+ *
+ * @tparam T The return type (e.g., float for sensor values)
+ * @tparam Args Optional arguments for the lambda
+ */
+template<typename T, typename... Args> class TemplateLambda {
+ public:
+  TemplateLambda() : f_(nullptr) {}
+
+  /** Set the lambda function pointer.
+   * INTERNAL API: Only for use by YAML codegen.
+   * Only stateless lambdas (no captures) are supported.
+   */
+  void set(optional<T> (*f)(Args...)) { this->f_ = f; }
+
+  /** Check if a lambda is set */
+  bool has_value() const { return this->f_ != nullptr; }
+
+  /** Call the lambda, returning nullopt if no lambda is set */
+  optional<T> operator()(Args &&...args) {
+    if (this->f_ == nullptr)
+      return nullopt;
+    return this->f_(std::forward<Args>(args)...);
+  }
+
+  /** Alias for operator() for compatibility */
+  optional<T> call(Args &&...args) { return (*this)(std::forward<Args>(args)...); }
+
+ protected:
+  optional<T> (*f_)(Args...);  // Function pointer (4 bytes on ESP32)
+};
+
+}  // namespace esphome

tests/components/template/common-base.yaml

@@ -9,6 +9,13 @@ esphome:
         id: template_sens
         state: !lambda "return 42.0;"
 
+    # Test C++ API: set_template() with stateless lambda (no captures)
+    # NOTE: set_template() is not intended to be a public API, but we test it to ensure it doesn't break.
+    - lambda: |-
+        id(template_sens).set_template([]() -> esphome::optional<float> {
+          return 123.0f;
+        });
+
     - datetime.date.set:
         id: test_date
         date:
@@ -215,6 +222,7 @@ cover:
 
 number:
   - platform: template
+    id: template_number
     name: "Template number"
     optimistic: true
     min_value: 0

tests/integration/fixtures/runtime_stats.yaml

@@ -32,6 +32,7 @@ switch:
     name: "Test Switch"
     id: test_switch
     optimistic: true
+    lambda: return false;
 
 interval:
   - interval: 0.5s