Single value header gets parsed as Vec

[muttleyxd]

I have encountered an interesting bug - trying to match a header value which contains a comma , results in incoming header value being parsed as Vec

What doesn't work, but I think it should

let mock_server = MockServer::start().await;

Mock::given(header("if-modified-since", "Sat, 02 Apr 2005 20:37:00 GMT")) // This is valid RFC2822
  .respond_with(ResponseTemplate::new(304))
  .expect(1)
  .mount(&mock_server)
  .await;

// This will return 404
let _result = reqwest::Client::new()
  .get(mock_server.uri())
  .header("if-modified-since", "Sat, 02 Apr 2005 20:37:00 GMT")
  .send()
  .await
  .unwrap()
  .error_for_status()
  .unwrap();

Workaround I found:

let mock_server = MockServer::start().await;

Mock::given(headers(
    "if-modified-since",
    vec!["Sat", "02 Apr 2005 20:37:00 GMT"],
  ))
  .respond_with(ResponseTemplate::new(304))
  .expect(1)
  .mount(&mock_server)
  .await;

// Returns 304
let _result = reqwest::Client::new()
    .get(mock_server.uri())
    .header("if-modified-since", "Sat, 02 Apr 2005 20:37:00 GMT")
    .send()
    .await
    .unwrap()
    .error_for_status()
    .unwrap();
}

I have prepared a repository with a test that reproduces the issue: https://github.com/muttleyxd/wiremock-header-matcher-bug/blob/master/src/main.rs