refactor: use incomplete instances to postpone lang info

php/servers/servers-rooms.php

@@ -156,6 +156,7 @@
 
 			if ($suppress_processing) return;
 
+			$this->language_flag = $details['language_flag'] ?? $this->get_language_flag();
 			$this->extract_tags_from_description();
 			$this->tags = isset($details['tags'])
 				? CommunityTag::from_details_array($details['tags'])
@@ -179,16 +180,12 @@
 		public function get_language_flag(): string {
 			global $languages;
 
-			$room_identifier = $this->get_room_identifier();
-			$server_pubkey = $this->server->get_pubkey();
-
 			if (isset($this->language_flag)) {
 				return $this->language_flag;
 			}
 
-			// Latter only applies to fetching stage
-			// where the language flag is serialized into JSON.
-			// Later stages deserialize the property and detect it above.
+			$room_identifier = $this->get_room_identifier();
+			$server_pubkey = $this->server->get_pubkey();
 
 			if (isset($languages[$room_identifier])) {
 				return $languages[$room_identifier];
@@ -666,6 +663,12 @@
 		 **/
 		private array $pubkey_candidates = [];
 
+		/**
+		 * @var array[] $_intermediate_room_data
+		 * Array of room details fetched before constructing room objects.
+		 */
+		private ?array $_intermediate_room_data = null;
+
 		/**
 		 * @var CommunityRoom[]|null $rooms
 		 * Array of Communities hosted by this server.
@@ -872,6 +875,7 @@
 		 */
 		function jsonSerialize(): array {
 			$details = get_object_vars($this);
+			unset($details['_intermediate_room_data']);
 			unset($details['room_hints']);
 			unset($details['merge_error']);
 			unset($details['pubkey_candidates']);
@@ -1002,6 +1006,7 @@
 				$fetch_job = function() use ($server, &$reachable_servers): Generator {
 					if (!yield from $server->fetch_rooms_coroutine()) return;
 					if (!yield from $server->fetch_pubkey_coroutine()) return;
+					$server->construct_rooms();
 					$reachable_servers[] = $server;
 				};
 				// passthrough hack
@@ -1310,7 +1315,7 @@
 				return false;
 			}
 
-			$this->rooms = CommunityRoom::from_details_array($this, $room_data);
+			$this->_intermediate_room_data = $room_data;
 
 			return true;
 		}
@@ -1324,7 +1329,7 @@
 
 			$base_url = $this->base_url;
 
-			if (empty($this->rooms)) {
+			if (empty($this->_intermediate_room_data)) {
 				log_warning("Server $base_url has no rooms to poll for public key");
 				return false;
 			}
@@ -1335,7 +1340,11 @@
 				return true;
 			}
 
-			$preview_url = $this->rooms[0]->get_preview_url();
+			// This is ugly. 'RoomBuilder' would be better.
+			$preview_url = CommunityRoom::_from_intermediate_data(
+				$this,
+				$this->_intermediate_room_data[0]
+			)->get_preview_url();
 
 			log_info("Fetching pubkey from $preview_url");
 			$room_view_response = yield from FetchingCoroutine