WebChannel tries to connect to localhost through proxy

In our application we have the following setup:

• a WebSocket Server which handles incoming connections
• a JS WebChannel client injected into a WebEngine page and connects directly to the WebSocket Server using localhost as a host address.

Without proxy, this setup works fine, however if the system has a proxy configured, it always tries to connect to this localhost address through proxy. If I explicitly exclude localhost in proxy settings of Windows, the connection works fine, but we can't depend on our users to set this option.

In the source of WebEngine, there is a rule which bypasses the proxy for 127.0.0.1 but that's inactive if the application uses the default proxy.

The corresponding line which adds that rule is this one:

proxy_config_service_qt.cpp @140 (net::ProxyConfigService::ConfigAvailability ProxyConfigServiceQt::GetLatestProxyConfig(net::ProxyConfigWithAnnotation *config))

    qtRules.bypass_rules.AddRuleToBypassLocal(); // don't use proxy for connections to localhost

But there is an early exit in the same function @106 in case of using the default proxy settings:

return systemAvailability;

My suggestion is that the bypass rule should be added in that case as well because there is no point in connecting to localhost throug a proxy.

In addition, the rule should match to 'localhost' as well, not just '127.0.0.1' and '[::1]' since it's being used regularly.