[core] Move build_info_data.h out of application.h to fix incremental rebuilds

build_info_data.h contains ESPHOME_BUILD_TIME which changes every build.
Since application.h included it, changing any source file caused
build_info_data.h to be rewritten (via sources_changed), which then
triggered a rebuild of every file that includes application.h.

Move all build_info_data.h dependent code from application.h inline
methods to application.cpp, so only application.cpp recompiles when
build info changes.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

esphome/components/version/version_text_sensor.cpp

@@ -25,7 +25,9 @@ void VersionTextSensor::setup() {
   if (!this->hide_timestamp_) {
     size_t len = strlen(version_str);
     ESPHOME_strncat_P(version_str, BUILT_STR, sizeof(version_str) - len - 1);
-    ESPHOME_strncat_P(version_str, ESPHOME_BUILD_TIME_STR, sizeof(version_str) - strlen(version_str) - 1);
+    char time_buf[esphome::Application::BUILD_TIME_STR_SIZE];
+    App.get_build_time_string(time_buf);
+    strncat(version_str, time_buf, sizeof(version_str) - strlen(version_str) - 1);
   }
 
   strncat(version_str, ")", sizeof(version_str) - strlen(version_str) - 1);

esphome/components/web_server/web_server.cpp

@@ -375,9 +375,8 @@ json::SerializationBuffer<> WebServer::get_config_json() {
   JsonObject root = builder.root();
 
   root[ESPHOME_F("title")] = App.get_friendly_name().empty() ? App.get_name().c_str() : App.get_friendly_name().c_str();
-  char comment_buffer[ESPHOME_COMMENT_SIZE];
-  App.get_comment_string(comment_buffer);
-  root[ESPHOME_F("comment")] = comment_buffer;
+  auto comment = App.get_comment();
+  root[ESPHOME_F("comment")] = comment.c_str();
 #if defined(USE_WEBSERVER_OTA_DISABLED) || !defined(USE_WEBSERVER_OTA)
   root[ESPHOME_F("ota")] = false;  // Note: USE_WEBSERVER_OTA_DISABLED only affects web_server, not captive_portal
 #else

esphome/core/application.cpp

@@ -749,4 +749,29 @@ void Application::get_build_time_string(std::span<char, BUILD_TIME_STR_SIZE> buf
   buffer[buffer.size() - 1] = '\0';
 }
 
+size_t Application::get_comment_size() { return ESPHOME_COMMENT_SIZE; }
+
+void Application::get_comment_string(char *buffer, size_t size) {
+  ESPHOME_strncpy_P(buffer, ESPHOME_COMMENT_STR, size);
+  buffer[size - 1] = '\0';
+}
+
+std::string Application::get_comment() {
+  char buffer[ESPHOME_COMMENT_SIZE];
+  this->get_comment_string(buffer, sizeof(buffer));
+  return std::string(buffer);
+}
+
+uint32_t Application::get_config_hash() { return ESPHOME_CONFIG_HASH; }
+
+uint32_t Application::get_config_version_hash() { return fnv1a_hash_extend(ESPHOME_CONFIG_HASH, ESPHOME_VERSION); }
+
+time_t Application::get_build_time() { return ESPHOME_BUILD_TIME; }
+
+std::string Application::get_compilation_time() {
+  char buf[BUILD_TIME_STR_SIZE];
+  this->get_build_time_string(buf);
+  return std::string(buf);
+}
+
 }  // namespace esphome

esphome/core/application.h

@@ -6,7 +6,6 @@
 #include <span>
 #include <string>
 #include <vector>
-#include "esphome/core/build_info_data.h"
 #include "esphome/core/component.h"
 #include "esphome/core/defines.h"
 #include "esphome/core/hal.h"
@@ -274,19 +273,14 @@ class Application {
     return "";
   }
 
+  /// Get the size of the comment buffer (including null terminator)
+  static size_t get_comment_size();
+
   /// Copy the comment string into the provided buffer
-  /// Buffer must be ESPHOME_COMMENT_SIZE bytes (compile-time enforced)
-  void get_comment_string(std::span<char, ESPHOME_COMMENT_SIZE> buffer) {
-    ESPHOME_strncpy_P(buffer.data(), ESPHOME_COMMENT_STR, buffer.size());
-    buffer[buffer.size() - 1] = '\0';
-  }
+  void get_comment_string(char *buffer, size_t size);
 
   /// Get the comment of this Application as a string
-  std::string get_comment() {
-    char buffer[ESPHOME_COMMENT_SIZE];
-    this->get_comment_string(buffer);
-    return std::string(buffer);
-  }
+  std::string get_comment();
 
   bool is_name_add_mac_suffix_enabled() const { return this->name_add_mac_suffix_; }
 
@@ -294,26 +288,22 @@ class Application {
   static constexpr size_t BUILD_TIME_STR_SIZE = 26;
 
   /// Get the config hash as a 32-bit integer
-  constexpr uint32_t get_config_hash() { return ESPHOME_CONFIG_HASH; }
+  uint32_t get_config_hash();
 
   /// Get the config hash extended with ESPHome version
-  constexpr uint32_t get_config_version_hash() { return fnv1a_hash_extend(ESPHOME_CONFIG_HASH, ESPHOME_VERSION); }
+  uint32_t get_config_version_hash();
 
   /// Get the build time as a Unix timestamp
-  constexpr time_t get_build_time() { return ESPHOME_BUILD_TIME; }
+  time_t get_build_time();
 
   /// Copy the build time string into the provided buffer
-  /// Buffer must be BUILD_TIME_STR_SIZE bytes (compile-time enforced)
+  /// Buffer must be BUILD_TIME_STR_SIZE bytes
   void get_build_time_string(std::span<char, BUILD_TIME_STR_SIZE> buffer);
 
   /// Get the build time as a string (deprecated, use get_build_time_string() instead)
   // Remove before 2026.7.0
   ESPDEPRECATED("Use get_build_time_string() instead. Removed in 2026.7.0", "2026.1.0")
-  std::string get_compilation_time() {
-    char buf[BUILD_TIME_STR_SIZE];
-    this->get_build_time_string(buf);
-    return std::string(buf);
-  }
+  std::string get_compilation_time();
 
   /// Get the cached time in milliseconds from when the current component started its loop execution
   inline uint32_t IRAM_ATTR HOT get_loop_component_start_time() const { return this->loop_component_start_time_; }