Logger logs unsent request headers even though Default in Client has restricted headers

[facewise]

Since the default class Default in Client uses sun.net.www.protocol.http.HttpURLConnection, which has the set of restricted headers, even if I add a header using RequestTemplate#header(String, String), the actual HTTP request does not contain the header.

However feign.Logger logs not the actual request but the Request made by SynchronousMethodHandler#executeAndDecode(), which contains the restricted header I have added.

This inconsistency made me hard to discover the problem because there's no such documentation tells the logged request may not be the same as the actual HTTP request.

I hope to add some documentation that tells RequestTemplate you applied may not be the actual request or, if possible, make Logger logs the actual HTTP request.

[velo]

Thanks, this is a fair documentation/API-observability gap: Logger sees Feign's Request, while the JDK client may still drop restricted headers before bytes go over the wire.

A docs PR that calls out that distinction would be welcome. If someone wants to change runtime logging instead, please keep it additive and covered with tests, since the actual sent request can be client-specific.