[mdns] Fix missing device info TXT records when native API is not enabled (#17520)

esphome/components/mdns/mdns_component.cpp

@@ -47,7 +47,7 @@ void MDNSComponent::setup_buffers_and_register_(PlatformRegisterFn platform_regi
   auto &services = services_storage;
 #endif
 
-#ifdef USE_API
+#ifdef USE_MDNS_DEVICE_INFO_TXT
 #ifdef USE_MDNS_STORE_SERVICES
   get_mac_address_into_buffer(this->mac_address_);
   char *mac_ptr = this->mac_address_;
@@ -70,17 +70,20 @@ void MDNSComponent::setup_buffers_and_register_(PlatformRegisterFn platform_regi
   platform_register(this, services);
 }
 
-void MDNSComponent::compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUNT> &services, char *mac_address_buf,
+void MDNSComponent::compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUNT> &services,
-                                     char *config_hash_buf) {
+                                     const char *mac_address_buf, const char *config_hash_buf) {
   // IMPORTANT: The #ifdef blocks below must match COMPONENTS_WITH_MDNS_SERVICES
   // in mdns/__init__.py. If you add a new service here, update both locations.
 
+#ifdef USE_MDNS_DEVICE_INFO_TXT
+  MDNS_STATIC_CONST_CHAR(TXT_VERSION, "version");
+  MDNS_STATIC_CONST_CHAR(TXT_MAC, "mac");
+  MDNS_STATIC_CONST_CHAR(TXT_CONFIG_HASH, "config_hash");
+#endif
+
 #ifdef USE_API
   MDNS_STATIC_CONST_CHAR(SERVICE_ESPHOMELIB, "_esphomelib");
   MDNS_STATIC_CONST_CHAR(TXT_FRIENDLY_NAME, "friendly_name");
-  MDNS_STATIC_CONST_CHAR(TXT_VERSION, "version");
-  MDNS_STATIC_CONST_CHAR(TXT_CONFIG_HASH, "config_hash");
-  MDNS_STATIC_CONST_CHAR(TXT_MAC, "mac");
   MDNS_STATIC_CONST_CHAR(TXT_PLATFORM, "platform");
   MDNS_STATIC_CONST_CHAR(TXT_BOARD, "board");
   MDNS_STATIC_CONST_CHAR(TXT_NETWORK, "network");
@@ -212,12 +215,18 @@ void MDNSComponent::compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUN
   web_service.service_type = MDNS_STR(SERVICE_HTTP);
   web_service.proto = MDNS_STR(SERVICE_TCP);
   web_service.port = []() -> uint16_t { return USE_WEBSERVER_PORT; };
+#ifndef USE_API
+  // Without the native API there is no _esphomelib service, so publish the
+  // device info here for the device builder to discover.
+  web_service.txt_records = {{MDNS_STR(TXT_VERSION), MDNS_STR(VALUE_VERSION)},
+                             {MDNS_STR(TXT_MAC), MDNS_STR(mac_address_buf)},
+                             {MDNS_STR(TXT_CONFIG_HASH), MDNS_STR(config_hash_buf)}};
+#endif
 #endif
 
 #if !defined(USE_API) && !defined(USE_PROMETHEUS) && !defined(USE_SENDSPIN) && !defined(USE_WEBSERVER) && \
     !defined(USE_MDNS_EXTRA_SERVICES)
   MDNS_STATIC_CONST_CHAR(SERVICE_HTTP, "_http");
-  MDNS_STATIC_CONST_CHAR(TXT_VERSION, "version");
 
   // Publish "http" service if not using native API or any other services
   // This is just to have *some* mDNS service so that .local resolution works
@@ -225,7 +234,9 @@ void MDNSComponent::compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUN
   fallback_service.service_type = MDNS_STR(SERVICE_HTTP);
   fallback_service.proto = MDNS_STR(SERVICE_TCP);
   fallback_service.port = []() -> uint16_t { return USE_WEBSERVER_PORT; };
-  fallback_service.txt_records = {{MDNS_STR(TXT_VERSION), MDNS_STR(VALUE_VERSION)}};
+  fallback_service.txt_records = {{MDNS_STR(TXT_VERSION), MDNS_STR(VALUE_VERSION)},
+                                  {MDNS_STR(TXT_MAC), MDNS_STR(mac_address_buf)},
+                                  {MDNS_STR(TXT_CONFIG_HASH), MDNS_STR(config_hash_buf)}};
 #endif
 }
 

esphome/components/mdns/mdns_component.h

@@ -22,6 +22,15 @@
 #endif
 #endif
 
+// Device info TXT records (version, mac, config_hash) are published on the _esphomelib service
+// when the native API is enabled, otherwise on the _http service (web_server's or the fallback one).
+// When neither applies (only prometheus, sendspin or user-defined services are configured), no
+// device info records are published and the buffers below are not needed.
+#if defined(USE_API) || defined(USE_WEBSERVER) || \
+    (!defined(USE_PROMETHEUS) && !defined(USE_SENDSPIN) && !defined(USE_MDNS_EXTRA_SERVICES))
+#define USE_MDNS_DEVICE_INFO_TXT
+#endif
+
 namespace esphome::mdns {
 
 // Helper struct that identifies strings that may be stored in flash storage (similar to LogString)
@@ -136,7 +145,7 @@ class MDNSComponent final : public Component
   StaticVector<std::string, MDNS_DYNAMIC_TXT_COUNT> dynamic_txt_values_;
 #endif
 
-#if defined(USE_API) && defined(USE_MDNS_STORE_SERVICES)
+#if defined(USE_MDNS_DEVICE_INFO_TXT) && defined(USE_MDNS_STORE_SERVICES)
   /// Fixed buffer for MAC address (only needed when services are stored)
   char mac_address_[MAC_ADDRESS_BUFFER_SIZE];
   /// Fixed buffer for config hash hex string (only needed when services are stored)
@@ -149,8 +158,8 @@ class MDNSComponent final : public Component
   // RP2040 defers MDNS.begin() until the first IP-up event; this tracks that.
   bool initialized_{false};
 #endif
-  void compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUNT> &services, char *mac_address_buf,
+  void compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUNT> &services, const char *mac_address_buf,
-                        char *config_hash_buf);
+                        const char *config_hash_buf);
 };
 
 }  // namespace esphome::mdns

esphome/components/mdns/mdns_host.cpp

@@ -12,7 +12,7 @@ namespace esphome::mdns {
 
 void MDNSComponent::setup() {
 #ifdef USE_MDNS_STORE_SERVICES
-#ifdef USE_API
+#ifdef USE_MDNS_DEVICE_INFO_TXT
   get_mac_address_into_buffer(this->mac_address_);
   char *mac_ptr = this->mac_address_;
   format_hex_to(this->config_hash_str_, App.get_config_hash());

tests/components/mdns/test-fallback.esp32-idf.yaml

@@ -0,0 +1,7 @@
+# No api, web_server or extra services so the fallback _http service
+# (with version, mac and config_hash TXT records) is compiled.
+wifi:
+  ssid: MySSID
+  password: password1
+
+mdns:

tests/components/mdns/test-webserver-no-api.esp32-idf.yaml

@@ -0,0 +1,9 @@
+# web_server without the native api so the version, mac and config_hash
+# TXT records are attached to the web_server _http service.
+wifi:
+  ssid: MySSID
+  password: password1
+
+web_server:
+
+mdns: