[web_server] Reduce flash usage by eliminating lambda overhead in JSON generation (#10749)

esphome/components/json/json_util.cpp

@@ -8,52 +8,12 @@ namespace json {
 
 static const char *const TAG = "json";
 
-#ifdef USE_PSRAM
-// Build an allocator for the JSON Library using the RAMAllocator class
-// This is only compiled when PSRAM is enabled
-struct SpiRamAllocator : ArduinoJson::Allocator {
-  void *allocate(size_t size) override { return this->allocator_.allocate(size); }
-
-  void deallocate(void *pointer) override {
-    // ArduinoJson's Allocator interface doesn't provide the size parameter in deallocate.
-    // RAMAllocator::deallocate() requires the size, which we don't have access to here.
-    // RAMAllocator::deallocate implementation just calls free() regardless of whether
-    // the memory was allocated with heap_caps_malloc or malloc.
-    // This is safe because ESP-IDF's heap implementation internally tracks the memory region
-    // and routes free() to the appropriate heap.
-    free(pointer);  // NOLINT(cppcoreguidelines-owning-memory,cppcoreguidelines-no-malloc)
-  }
-
-  void *reallocate(void *ptr, size_t new_size) override {
-    return this->allocator_.reallocate(static_cast<uint8_t *>(ptr), new_size);
-  }
-
- protected:
-  RAMAllocator<uint8_t> allocator_{RAMAllocator<uint8_t>(RAMAllocator<uint8_t>::NONE)};
-};
-#endif
-
 std::string build_json(const json_build_t &f) {
   // NOLINTBEGIN(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
-#ifdef USE_PSRAM
+  JsonBuilder builder;
-  auto doc_allocator = SpiRamAllocator();
+  JsonObject root = builder.root();
-  JsonDocument json_document(&doc_allocator);
-#else
-  JsonDocument json_document;
-#endif
-  if (json_document.overflowed()) {
-    ESP_LOGE(TAG, "Could not allocate memory for JSON document!");
-    return "{}";
-  }
-  JsonObject root = json_document.to<JsonObject>();
   f(root);
-  if (json_document.overflowed()) {
+  return builder.serialize();
-    ESP_LOGE(TAG, "Could not allocate memory for JSON document!");
-    return "{}";
-  }
-  std::string output;
-  serializeJson(json_document, output);
-  return output;
   // NOLINTEND(clang-analyzer-cplusplus.NewDeleteLeaks)
 }
 
@@ -84,5 +44,15 @@ bool parse_json(const std::string &data, const json_parse_t &f) {
   // NOLINTEND(clang-analyzer-cplusplus.NewDeleteLeaks)
 }
 
+std::string JsonBuilder::serialize() {
+  if (doc_.overflowed()) {
+    ESP_LOGE(TAG, "JSON document overflow");
+    return "{}";
+  }
+  std::string output;
+  serializeJson(doc_, output);
+  return output;
+}
+
 }  // namespace json
 }  // namespace esphome

esphome/components/json/json_util.h

@@ -13,6 +13,31 @@
 namespace esphome {
 namespace json {
 
+#ifdef USE_PSRAM
+// Build an allocator for the JSON Library using the RAMAllocator class
+// This is only compiled when PSRAM is enabled
+struct SpiRamAllocator : ArduinoJson::Allocator {
+  void *allocate(size_t size) override { return allocator_.allocate(size); }
+
+  void deallocate(void *ptr) override {
+    // ArduinoJson's Allocator interface doesn't provide the size parameter in deallocate.
+    // RAMAllocator::deallocate() requires the size, which we don't have access to here.
+    // RAMAllocator::deallocate implementation just calls free() regardless of whether
+    // the memory was allocated with heap_caps_malloc or malloc.
+    // This is safe because ESP-IDF's heap implementation internally tracks the memory region
+    // and routes free() to the appropriate heap.
+    free(ptr);  // NOLINT(cppcoreguidelines-owning-memory,cppcoreguidelines-no-malloc)
+  }
+
+  void *reallocate(void *ptr, size_t new_size) override {
+    return allocator_.reallocate(static_cast<uint8_t *>(ptr), new_size);
+  }
+
+ protected:
+  RAMAllocator<uint8_t> allocator_{RAMAllocator<uint8_t>::NONE};
+};
+#endif
+
 /// Callback function typedef for parsing JsonObjects.
 using json_parse_t = std::function<bool(JsonObject)>;
 
@@ -25,5 +50,29 @@ std::string build_json(const json_build_t &f);
 /// Parse a JSON string and run the provided json parse function if it's valid.
 bool parse_json(const std::string &data, const json_parse_t &f);
 
+/// Builder class for creating JSON documents without lambdas
+class JsonBuilder {
+ public:
+  JsonObject root() {
+    if (!root_created_) {
+      root_ = doc_.to<JsonObject>();
+      root_created_ = true;
+    }
+    return root_;
+  }
+
+  std::string serialize();
+
+ private:
+#ifdef USE_PSRAM
+  SpiRamAllocator allocator_;
+  JsonDocument doc_{&allocator_};
+#else
+  JsonDocument doc_;
+#endif
+  JsonObject root_;
+  bool root_created_{false};
+};
+
 }  // namespace json
 }  // namespace esphome

esphome/components/web_server/web_server.cpp

@@ -228,10 +228,11 @@ void DeferredUpdateEventSourceList::on_client_connect_(WebServer *ws, DeferredUp
 
 #ifdef USE_WEBSERVER_SORTING
   for (auto &group : ws->sorting_groups_) {
-    message = json::build_json([group](JsonObject root) {
+    json::JsonBuilder builder;
+    JsonObject root = builder.root();
     root["name"] = group.second.name;
     root["sorting_weight"] = group.second.weight;
-    });
+    message = builder.serialize();
 
     // up to 31 groups should be able to be queued initially without defer
     source->try_send_nodefer(message.c_str(), "sorting_group");
@@ -265,7 +266,9 @@ void WebServer::set_js_include(const char *js_include) { this->js_include_ = js_
 #endif
 
 std::string WebServer::get_config_json() {
-  return json::build_json([this](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   root["title"] = App.get_friendly_name().empty() ? App.get_name() : App.get_friendly_name();
   root["comment"] = App.get_comment();
 #if defined(USE_WEBSERVER_OTA_DISABLED) || !defined(USE_WEBSERVER_OTA)
@@ -275,7 +278,8 @@ std::string WebServer::get_config_json() {
 #endif
   root["log"] = this->expose_log_;
   root["lang"] = "en";
-  });
+
+  return builder.serialize();
 }
 
 void WebServer::setup() {
@@ -435,7 +439,10 @@ std::string WebServer::sensor_all_json_generator(WebServer *web_server, void *so
   return web_server->sensor_json((sensor::Sensor *) (source), ((sensor::Sensor *) (source))->state, DETAIL_ALL);
 }
 std::string WebServer::sensor_json(sensor::Sensor *obj, float value, JsonDetail start_config) {
-  return json::build_json([this, obj, value, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
+  // Build JSON directly inline
   std::string state;
   if (std::isnan(value)) {
     state = "NA";
@@ -450,7 +457,8 @@ std::string WebServer::sensor_json(sensor::Sensor *obj, float value, JsonDetail
     if (!obj->get_unit_of_measurement().empty())
       root["uom"] = obj->get_unit_of_measurement();
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -483,12 +491,15 @@ std::string WebServer::text_sensor_all_json_generator(WebServer *web_server, voi
 }
 std::string WebServer::text_sensor_json(text_sensor::TextSensor *obj, const std::string &value,
                                         JsonDetail start_config) {
-  return json::build_json([this, obj, value, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_icon_state_value(root, obj, "text_sensor-" + obj->get_object_id(), value, value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -553,13 +564,16 @@ std::string WebServer::switch_all_json_generator(WebServer *web_server, void *so
   return web_server->switch_json((switch_::Switch *) (source), ((switch_::Switch *) (source))->state, DETAIL_ALL);
 }
 std::string WebServer::switch_json(switch_::Switch *obj, bool value, JsonDetail start_config) {
-  return json::build_json([this, obj, value, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_icon_state_value(root, obj, "switch-" + obj->get_object_id(), value ? "ON" : "OFF", value, start_config);
   if (start_config == DETAIL_ALL) {
     root["assumed_state"] = obj->assumed_state();
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -590,12 +604,15 @@ std::string WebServer::button_all_json_generator(WebServer *web_server, void *so
   return web_server->button_json((button::Button *) (source), DETAIL_ALL);
 }
 std::string WebServer::button_json(button::Button *obj, JsonDetail start_config) {
-  return json::build_json([this, obj, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_id(root, obj, "button-" + obj->get_object_id(), start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -627,13 +644,16 @@ std::string WebServer::binary_sensor_all_json_generator(WebServer *web_server, v
                                         ((binary_sensor::BinarySensor *) (source))->state, DETAIL_ALL);
 }
 std::string WebServer::binary_sensor_json(binary_sensor::BinarySensor *obj, bool value, JsonDetail start_config) {
-  return json::build_json([this, obj, value, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_icon_state_value(root, obj, "binary_sensor-" + obj->get_object_id(), value ? "ON" : "OFF", value,
                             start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -694,7 +714,9 @@ std::string WebServer::fan_all_json_generator(WebServer *web_server, void *sourc
   return web_server->fan_json((fan::Fan *) (source), DETAIL_ALL);
 }
 std::string WebServer::fan_json(fan::Fan *obj, JsonDetail start_config) {
-  return json::build_json([this, obj, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_icon_state_value(root, obj, "fan-" + obj->get_object_id(), obj->state ? "ON" : "OFF", obj->state,
                             start_config);
   const auto traits = obj->get_traits();
@@ -707,7 +729,8 @@ std::string WebServer::fan_json(fan::Fan *obj, JsonDetail start_config) {
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -767,7 +790,9 @@ std::string WebServer::light_all_json_generator(WebServer *web_server, void *sou
   return web_server->light_json((light::LightState *) (source), DETAIL_ALL);
 }
 std::string WebServer::light_json(light::LightState *obj, JsonDetail start_config) {
-  return json::build_json([this, obj, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_id(root, obj, "light-" + obj->get_object_id(), start_config);
   root["state"] = obj->remote_values.is_on() ? "ON" : "OFF";
 
@@ -780,7 +805,8 @@ std::string WebServer::light_json(light::LightState *obj, JsonDetail start_confi
     }
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -839,7 +865,9 @@ std::string WebServer::cover_all_json_generator(WebServer *web_server, void *sou
   return web_server->cover_json((cover::Cover *) (source), DETAIL_ALL);
 }
 std::string WebServer::cover_json(cover::Cover *obj, JsonDetail start_config) {
-  return json::build_json([this, obj, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_icon_state_value(root, obj, "cover-" + obj->get_object_id(), obj->is_fully_closed() ? "CLOSED" : "OPEN",
                             obj->position, start_config);
   root["current_operation"] = cover::cover_operation_to_str(obj->current_operation);
@@ -851,7 +879,8 @@ std::string WebServer::cover_json(cover::Cover *obj, JsonDetail start_config) {
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -894,15 +923,16 @@ std::string WebServer::number_all_json_generator(WebServer *web_server, void *so
   return web_server->number_json((number::Number *) (source), ((number::Number *) (source))->state, DETAIL_ALL);
 }
 std::string WebServer::number_json(number::Number *obj, float value, JsonDetail start_config) {
-  return json::build_json([this, obj, value, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_id(root, obj, "number-" + obj->get_object_id(), start_config);
   if (start_config == DETAIL_ALL) {
     root["min_value"] =
         value_accuracy_to_string(obj->traits.get_min_value(), step_to_accuracy_decimals(obj->traits.get_step()));
     root["max_value"] =
         value_accuracy_to_string(obj->traits.get_max_value(), step_to_accuracy_decimals(obj->traits.get_step()));
-      root["step"] =
+    root["step"] = value_accuracy_to_string(obj->traits.get_step(), step_to_accuracy_decimals(obj->traits.get_step()));
-          value_accuracy_to_string(obj->traits.get_step(), step_to_accuracy_decimals(obj->traits.get_step()));
     root["mode"] = (int) obj->traits.get_mode();
     if (!obj->traits.get_unit_of_measurement().empty())
       root["uom"] = obj->traits.get_unit_of_measurement();
@@ -918,7 +948,8 @@ std::string WebServer::number_json(number::Number *obj, float value, JsonDetail
       state += " " + obj->traits.get_unit_of_measurement();
     root["state"] = state;
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -966,7 +997,9 @@ std::string WebServer::date_all_json_generator(WebServer *web_server, void *sour
   return web_server->date_json((datetime::DateEntity *) (source), DETAIL_ALL);
 }
 std::string WebServer::date_json(datetime::DateEntity *obj, JsonDetail start_config) {
-  return json::build_json([this, obj, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_id(root, obj, "date-" + obj->get_object_id(), start_config);
   std::string value = str_sprintf("%d-%02d-%02d", obj->year, obj->month, obj->day);
   root["value"] = value;
@@ -974,7 +1007,8 @@ std::string WebServer::date_json(datetime::DateEntity *obj, JsonDetail start_con
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif  // USE_DATETIME_DATE
 
@@ -1021,7 +1055,9 @@ std::string WebServer::time_all_json_generator(WebServer *web_server, void *sour
   return web_server->time_json((datetime::TimeEntity *) (source), DETAIL_ALL);
 }
 std::string WebServer::time_json(datetime::TimeEntity *obj, JsonDetail start_config) {
-  return json::build_json([this, obj, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_id(root, obj, "time-" + obj->get_object_id(), start_config);
   std::string value = str_sprintf("%02d:%02d:%02d", obj->hour, obj->minute, obj->second);
   root["value"] = value;
@@ -1029,7 +1065,8 @@ std::string WebServer::time_json(datetime::TimeEntity *obj, JsonDetail start_con
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif  // USE_DATETIME_TIME
 
@@ -1076,16 +1113,19 @@ std::string WebServer::datetime_all_json_generator(WebServer *web_server, void *
   return web_server->datetime_json((datetime::DateTimeEntity *) (source), DETAIL_ALL);
 }
 std::string WebServer::datetime_json(datetime::DateTimeEntity *obj, JsonDetail start_config) {
-  return json::build_json([this, obj, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_id(root, obj, "datetime-" + obj->get_object_id(), start_config);
-    std::string value = str_sprintf("%d-%02d-%02d %02d:%02d:%02d", obj->year, obj->month, obj->day, obj->hour,
+  std::string value =
-                                    obj->minute, obj->second);
+      str_sprintf("%d-%02d-%02d %02d:%02d:%02d", obj->year, obj->month, obj->day, obj->hour, obj->minute, obj->second);
   root["value"] = value;
   root["state"] = value;
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif  // USE_DATETIME_DATETIME
 
@@ -1128,7 +1168,9 @@ std::string WebServer::text_all_json_generator(WebServer *web_server, void *sour
   return web_server->text_json((text::Text *) (source), ((text::Text *) (source))->state, DETAIL_ALL);
 }
 std::string WebServer::text_json(text::Text *obj, const std::string &value, JsonDetail start_config) {
-  return json::build_json([this, obj, value, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_id(root, obj, "text-" + obj->get_object_id(), start_config);
   root["min_length"] = obj->traits.get_min_length();
   root["max_length"] = obj->traits.get_max_length();
@@ -1143,7 +1185,8 @@ std::string WebServer::text_json(text::Text *obj, const std::string &value, Json
     root["mode"] = (int) obj->traits.get_mode();
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -1186,7 +1229,9 @@ std::string WebServer::select_all_json_generator(WebServer *web_server, void *so
   return web_server->select_json((select::Select *) (source), ((select::Select *) (source))->state, DETAIL_ALL);
 }
 std::string WebServer::select_json(select::Select *obj, const std::string &value, JsonDetail start_config) {
-  return json::build_json([this, obj, value, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_icon_state_value(root, obj, "select-" + obj->get_object_id(), value, value, start_config);
   if (start_config == DETAIL_ALL) {
     JsonArray opt = root["option"].to<JsonArray>();
@@ -1195,7 +1240,8 @@ std::string WebServer::select_json(select::Select *obj, const std::string &value
     }
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -1244,14 +1290,17 @@ void WebServer::handle_climate_request(AsyncWebServerRequest *request, const Url
   request->send(404);
 }
 std::string WebServer::climate_state_json_generator(WebServer *web_server, void *source) {
+  // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   return web_server->climate_json((climate::Climate *) (source), DETAIL_STATE);
 }
 std::string WebServer::climate_all_json_generator(WebServer *web_server, void *source) {
+  // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   return web_server->climate_json((climate::Climate *) (source), DETAIL_ALL);
 }
 std::string WebServer::climate_json(climate::Climate *obj, JsonDetail start_config) {
   // NOLINTBEGIN(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
-  return json::build_json([this, obj, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
   set_json_id(root, obj, "climate-" + obj->get_object_id(), start_config);
   const auto traits = obj->get_traits();
   int8_t target_accuracy = traits.get_target_temperature_accuracy_decimals();
@@ -1335,7 +1384,8 @@ std::string WebServer::climate_json(climate::Climate *obj, JsonDetail start_conf
     if (!has_state)
       root["state"] = root["target_temperature"];
   }
-  });
+
+  return builder.serialize();
   // NOLINTEND(clang-analyzer-cplusplus.NewDeleteLeaks)
 }
 #endif
@@ -1401,13 +1451,16 @@ std::string WebServer::lock_all_json_generator(WebServer *web_server, void *sour
   return web_server->lock_json((lock::Lock *) (source), ((lock::Lock *) (source))->state, DETAIL_ALL);
 }
 std::string WebServer::lock_json(lock::Lock *obj, lock::LockState value, JsonDetail start_config) {
-  return json::build_json([this, obj, value, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_icon_state_value(root, obj, "lock-" + obj->get_object_id(), lock::lock_state_to_string(value), value,
                             start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -1464,7 +1517,9 @@ std::string WebServer::valve_all_json_generator(WebServer *web_server, void *sou
   return web_server->valve_json((valve::Valve *) (source), DETAIL_ALL);
 }
 std::string WebServer::valve_json(valve::Valve *obj, JsonDetail start_config) {
-  return json::build_json([this, obj, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_icon_state_value(root, obj, "valve-" + obj->get_object_id(), obj->is_fully_closed() ? "CLOSED" : "OPEN",
                             obj->position, start_config);
   root["current_operation"] = valve::valve_operation_to_str(obj->current_operation);
@@ -1474,7 +1529,8 @@ std::string WebServer::valve_json(valve::Valve *obj, JsonDetail start_config) {
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -1533,14 +1589,17 @@ std::string WebServer::alarm_control_panel_all_json_generator(WebServer *web_ser
 std::string WebServer::alarm_control_panel_json(alarm_control_panel::AlarmControlPanel *obj,
                                                 alarm_control_panel::AlarmControlPanelState value,
                                                 JsonDetail start_config) {
-  return json::build_json([this, obj, value, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   char buf[16];
   set_json_icon_state_value(root, obj, "alarm-control-panel-" + obj->get_object_id(),
                             PSTR_LOCAL(alarm_control_panel_state_to_string(value)), value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -1577,7 +1636,9 @@ std::string WebServer::event_all_json_generator(WebServer *web_server, void *sou
   return web_server->event_json(event, get_event_type(event), DETAIL_ALL);
 }
 std::string WebServer::event_json(event::Event *obj, const std::string &event_type, JsonDetail start_config) {
-  return json::build_json([this, obj, event_type, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_id(root, obj, "event-" + obj->get_object_id(), start_config);
   if (!event_type.empty()) {
     root["event_type"] = event_type;
@@ -1590,7 +1651,8 @@ std::string WebServer::event_json(event::Event *obj, const std::string &event_ty
     root["device_class"] = obj->get_device_class();
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
 }
 #endif
 
@@ -1637,14 +1699,18 @@ void WebServer::handle_update_request(AsyncWebServerRequest *request, const UrlM
   request->send(404);
 }
 std::string WebServer::update_state_json_generator(WebServer *web_server, void *source) {
+  // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   return web_server->update_json((update::UpdateEntity *) (source), DETAIL_STATE);
 }
 std::string WebServer::update_all_json_generator(WebServer *web_server, void *source) {
+  // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   return web_server->update_json((update::UpdateEntity *) (source), DETAIL_STATE);
 }
 std::string WebServer::update_json(update::UpdateEntity *obj, JsonDetail start_config) {
   // NOLINTBEGIN(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
-  return json::build_json([this, obj, start_config](JsonObject root) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
   set_json_id(root, obj, "update-" + obj->get_object_id(), start_config);
   root["value"] = obj->update_info.latest_version;
   root["state"] = update_state_to_string(obj->state);
@@ -1655,7 +1721,8 @@ std::string WebServer::update_json(update::UpdateEntity *obj, JsonDetail start_c
     root["release_url"] = obj->update_info.release_url;
     this->add_sorting_info_(root, obj);
   }
-  });
+
+  return builder.serialize();
   // NOLINTEND(clang-analyzer-cplusplus.NewDeleteLeaks)
 }
 #endif

esphome/components/web_server_idf/web_server_idf.cpp

@@ -317,8 +317,8 @@ AsyncEventSource::~AsyncEventSource() {
 }
 
 void AsyncEventSource::handleRequest(AsyncWebServerRequest *request) {
-  auto *rsp =  // NOLINT(cppcoreguidelines-owning-memory)
+  // NOLINTNEXTLINE(cppcoreguidelines-owning-memory,clang-analyzer-cplusplus.NewDeleteLeaks)
-      new AsyncEventSourceResponse(request, this, this->web_server_);
+  auto *rsp = new AsyncEventSourceResponse(request, this, this->web_server_);
   if (this->on_connect_) {
     this->on_connect_(rsp);
   }
@@ -392,10 +392,11 @@ AsyncEventSourceResponse::AsyncEventSourceResponse(const AsyncWebServerRequest *
 #ifdef USE_WEBSERVER_SORTING
   for (auto &group : ws->sorting_groups_) {
     // NOLINTBEGIN(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
-    message = json::build_json([group](JsonObject root) {
+    json::JsonBuilder builder;
+    JsonObject root = builder.root();
     root["name"] = group.second.name;
     root["sorting_weight"] = group.second.weight;
-    });
+    message = builder.serialize();
     // NOLINTEND(clang-analyzer-cplusplus.NewDeleteLeaks)
 
     // a (very) large number of these should be able to be queued initially without defer