network: add oneserver/auto_connect both enabled checks, avoid connecting to random/multiple servers

if oneserver is enabled.

electrum/network.py

@@ -601,6 +601,13 @@ class Network(Logger, NetworkRetryManager[ServerAddr]):
     def _init_parameters_from_config(self) -> None:
         dns_hacks.configure_dns_resolver()
         self.auto_connect = self.config.NETWORK_AUTO_CONNECT
+        if self.auto_connect and self.config.NETWORK_ONESERVER:
+            # enabling both oneserver and auto_connect doesn't really make sense
+            # assume oneserver is enabled for privacy reasons, disable auto_connect and assume server is unpredictable
+            self.logger.warning(f'both "oneserver" and "auto_connect" options enabled, disabling "auto_connect" and resetting "server".')
+            self.config.NETWORK_SERVER = ""  # let _set_default_server set harmless default (localhost)
+            self.auto_connect = False
+
         self._set_default_server()
         self._set_proxy(ProxySettings.from_config(self.config))
         self._maybe_set_oneserver()
@@ -722,7 +729,12 @@ class Network(Logger, NetworkRetryManager[ServerAddr]):
                 self.logger.warning(f'failed to parse server-string ({server!r}); falling back to localhost:1:s.')
                 self.default_server = ServerAddr.from_str("localhost:1:s")
         else:
-            self.default_server = pick_random_server(allowed_protocols=self._allowed_protocols)
+            # if oneserver is enabled but no server specified then don't pick a random server
+            if self.config.NETWORK_ONESERVER:
+                self.logger.warning(f'"oneserver" option enabled, but no "server" defined; falling back to localhost:1:s.')
+                self.default_server = ServerAddr.from_str("localhost:1:s")
+            else:
+                self.default_server = pick_random_server(allowed_protocols=self._allowed_protocols)
         assert isinstance(self.default_server, ServerAddr), f"invalid type for default_server: {self.default_server!r}"
 
     def _set_proxy(self, proxy: ProxySettings):

electrum/wizard.py

@@ -753,8 +753,6 @@ class ServerConnectWizard(AbstractWizard):
                     raise Exception('failed to parse server %s' % wizard_data['server'])
             except Exception:
                 return
-        else:
-            oneserver = False
         net_params = net_params._replace(server=server, auto_connect=wizard_data['autoconnect'], oneserver=oneserver)
         self._daemon.network.run_from_another_thread(self._daemon.network.set_parameters(net_params))