Add support for button entities (#2824)

esphome/components/mqtt/mqtt_button.cpp

@@ -0,0 +1,40 @@
+#include "mqtt_button.h"
+#include "esphome/core/log.h"
+
+#include "mqtt_const.h"
+
+#ifdef USE_MQTT
+#ifdef USE_BUTTON
+
+namespace esphome {
+namespace mqtt {
+
+static const char *const TAG = "mqtt.button";
+
+using namespace esphome::button;
+
+MQTTButtonComponent::MQTTButtonComponent(button::Button *button) : MQTTComponent(), button_(button) {}
+
+void MQTTButtonComponent::setup() {
+  this->subscribe(this->get_command_topic_(), [this](const std::string &topic, const std::string &payload) {
+    if (payload == "press") {
+      this->button_->press();
+    } else {
+      ESP_LOGW(TAG, "'%s': Received unknown status payload: %s", this->friendly_name().c_str(), payload.c_str());
+      this->status_momentary_warning("state", 5000);
+    }
+  });
+}
+void MQTTButtonComponent::dump_config() {
+  ESP_LOGCONFIG(TAG, "MQTT Button '%s': ", this->button_->get_name().c_str());
+  LOG_MQTT_COMPONENT(true, true);
+}
+
+std::string MQTTButtonComponent::component_type() const { return "button"; }
+const EntityBase *MQTTButtonComponent::get_entity() const { return this->button_; }
+
+}  // namespace mqtt
+}  // namespace esphome
+
+#endif
+#endif  // USE_MQTT