HttpRequest doesn't send parameters added in Authenticator

[hmG3]

Describe the bug
After upgrading from version 109.1 to 110.0 I noticed some of our logic is broken.
A typical use case for us is to add security headers during the authentication flow.

public override ValueTask Authenticate(IRestClient client, RestRequest request)
{
 request.AddOrUpdateParameter("X-Security-Param", "generated-security-hash");
 return ValueTask.CompletedTask;
}

However, it doesn't work when sending requests with form data.

While investigating, I found that now when building RequestContent

RestSharp/src/RestSharp/RestClient.Async.cs

Line 89 in edce8c9

using var requestContent = new RequestContent(this, request);

for HttpRequestMessage it adds only cached params

RestSharp/src/RestSharp/Request/RequestContent.cs

Line 41 in edce8c9

var postParameters = _parameters.GetContentParameters(_request.Method).ToArray();

but not ones added by Authenticator

RestSharp/src/RestSharp/RestClient.Async.cs

Line 92 in edce8c9

if (authenticator != null) await authenticator.Authenticate(this, request).ConfigureAwait(false);

To Reproduce

public class RestWrapper : IAuthenticator
{
 private readonly RestClient _restClient;

 public RestWrapper()
 {
 _restClient = new RestClient(new RestClientOptions
 {
 BaseUrl = new Uri("https://localhost"),
 Authenticator = this
 });
 }

 public ValueTask Authenticate(IRestClient client, RestRequest request)
 {
 request.AddParameter("X-Security-Param", "generated-security-hash");
 return ValueTask.CompletedTask;
 }

 public void SendRequest()
 {
 var testRequest = new RestRequest("api/v1/endpoint", Method.Post);
 testRequest.AddParameter("scope", "test");

 _restClient.Execute(testRequest);
 }
}

new RestWrapper().SendRequest() // server failure - missing X-Security-Param

[alexeyzimarev]

Yes, it can be fixed by moving the authenticator call a couple of lines up.

The reason why it works in most cases is that people usually use the authorisation header, and headers are added later.