`findProxy` and `findProxyFromEnvironment` should be async

[yamsergey]

Dart provides us with possibility to add proxy for HTTP/HTTPS requests.

To do that, developers advised to implement one of the methods:

sdk/sdk/lib/_http/http.dart

Line 1776 in d63d5d9

void set findProxy(String f(Uri url)?);

sdk/sdk/lib/_http/http.dart

Line 1829 in d63d5d9

static String findProxyFromEnvironment(Uri url,

Also in documentation:
https://api.dart.dev/stable/2.10.5/dart-io/HttpClient/findProxy.html
https://api.flutter.dev/flutter/dart-io/HttpClient/findProxyFromEnvironment.html

Unfortunately all the options are synchronous. And at the same time proxy configuration could be way more complex than just host and port stored in environment variables. There could be excluded urls or Auto Proxy configuration, which will require async calls.

[c15yi]

Is there a solution to work with Auto Proxy Configuration (.pac file)? All plugins I could find so far only read out the manual proxy configuration and return nothing for automatic proxy configuration which is not helpful when setting up the proxy in flutter.

[marceloadsj]

@ChristianNavolskyi maybe this could help you:
https://github.com/BrowserStackCE/flutter_system_proxy/blob/main/lib/flutter_system_proxy.dart#L73

It's for flutter but maybe you can find something useful over there.

Edit: ops, now I read you're actually looking for something in flutter, 😅. I've used the pkg above and it definitely works with .pac file over url. hehe

[c15yi]

Thanks for the suggestion. I tried it out, but somehow it always returned "undefined" for the URLs I passed it instead of "DIRECT" or the actual proxy.

During debugging, I saw that it got the pac file correctly, but it seems like it has problems evaluating it on the native side.

Do you have any idea why that could be?

With another package I found on GitLab it works, so the pac file and everything should be correct.

[marceloadsj]

Hummm, are you able to post your pac file here? (Ofc, feel free to hide any sensitive info, IPs or anything!)

I just want to double check it to see if I find anything weird. Hehe

[c15yi]

Yes of course, had to change the file ending to txt because GitHub doesn't support pac.
proxy-default.txt

Thanks for your support!

[marceloadsj]

Alright, the .pac seems to be okay. I will try to test the setup soon and let you know.

For my other app, I used the "advanced setup" from https://github.com/BrowserStackCE/flutter_system_proxy#advanced-usage-custom-dio-adapter

Let me know if you find something. I do the same from my side. Hehe 😅