[web_server] Simplify datetime formatting with buf_append_printf

esphome/components/uptime/text_sensor/uptime_text_sensor.cpp

@@ -9,12 +9,17 @@ namespace uptime {
 
 static const char *const TAG = "uptime.sensor";
 
+// Clamp position to valid buffer range when snprintf indicates truncation
+static size_t clamp_buffer_pos(size_t pos, size_t buf_size) { return pos < buf_size ? pos : buf_size - 1; }
+
 static void append_unit(char *buf, size_t buf_size, size_t &pos, const char *separator, unsigned value,
                         const char *label) {
   if (pos > 0) {
-    pos = buf_append_printf(buf, buf_size, pos, "%s", separator);
+    pos += snprintf(buf + pos, buf_size - pos, "%s", separator);
+    pos = clamp_buffer_pos(pos, buf_size);
   }
-  pos = buf_append_printf(buf, buf_size, pos, "%u%s", value, label);
+  pos += snprintf(buf + pos, buf_size - pos, "%u%s", value, label);
+  pos = clamp_buffer_pos(pos, buf_size);
 }
 
 void UptimeTextSensor::setup() {

esphome/components/web_server/web_server.cpp

@@ -1178,11 +1178,7 @@ std::string WebServer::date_json_(datetime::DateEntity *obj, JsonDetail start_co
 
   // Format: YYYY-MM-DD (max 10 chars + null)
   char value[12];
-#ifdef USE_ESP8266
-  snprintf_P(value, sizeof(value), PSTR("%d-%02d-%02d"), obj->year, obj->month, obj->day);
-#else
-  snprintf(value, sizeof(value), "%d-%02d-%02d", obj->year, obj->month, obj->day);
-#endif
+  buf_append_printf(value, sizeof(value), 0, "%d-%02d-%02d", obj->year, obj->month, obj->day);
   set_json_icon_state_value(root, obj, "date", value, value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
@@ -1241,11 +1237,7 @@ std::string WebServer::time_json_(datetime::TimeEntity *obj, JsonDetail start_co
 
   // Format: HH:MM:SS (8 chars + null)
   char value[12];
-#ifdef USE_ESP8266
-  snprintf_P(value, sizeof(value), PSTR("%02d:%02d:%02d"), obj->hour, obj->minute, obj->second);
-#else
-  snprintf(value, sizeof(value), "%02d:%02d:%02d", obj->hour, obj->minute, obj->second);
-#endif
+  buf_append_printf(value, sizeof(value), 0, "%02d:%02d:%02d", obj->hour, obj->minute, obj->second);
   set_json_icon_state_value(root, obj, "time", value, value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
@@ -1304,13 +1296,8 @@ std::string WebServer::datetime_json_(datetime::DateTimeEntity *obj, JsonDetail
 
   // Format: YYYY-MM-DD HH:MM:SS (max 19 chars + null)
   char value[24];
-#ifdef USE_ESP8266
-  snprintf_P(value, sizeof(value), PSTR("%d-%02d-%02d %02d:%02d:%02d"), obj->year, obj->month, obj->day, obj->hour,
-             obj->minute, obj->second);
-#else
-  snprintf(value, sizeof(value), "%d-%02d-%02d %02d:%02d:%02d", obj->year, obj->month, obj->day, obj->hour, obj->minute,
-           obj->second);
-#endif
+  buf_append_printf(value, sizeof(value), 0, "%d-%02d-%02d %02d:%02d:%02d", obj->year, obj->month, obj->day, obj->hour,
+                    obj->minute, obj->second);
   set_json_icon_state_value(root, obj, "datetime", value, value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);