Ktor sets default User-Agent even though custom one is defined in Default Headers

Ktor Version and Engine Used (client or server and name) ktor-client-apache:1.3.1

Describe the bug Default “Ktor client” User-Agent is set even if User-Agent header value was previously configured using .setDefaultHeaders() for client.

To Reproduce Steps to reproduce the behavior:

1. Create client instance and setDefaultHeader User-Agent:

val client = HttpClient(Apache) {
    engine {
        customizeClient {
            setDefaultHeaders(mapOf(
                "User-Agent" to "Test Agent"
            ).map { BasicHeader(it.key, it.value) })
        }
    }
}

1. Perform any request:

client.request<String>("https://google.com/") {
            method = HttpMethod.Get
}

Expected behavior Request is done using User-Agent that was configured for the client using default headers and not default User-Agent for Ktor

Result Request is done using default Ktor UA header: Ktor client and not Test Agent that was sent when initializing client

Code issues The problem is in ktor-client-core-jvm-1.3.1-sources.jar!/commonMain/io/ktor/client/engine/Utils.kt class. It checks if there’s UA header in request itself or in content headers but never checks client default headers. Here are the corresponding lines of code:

    val missingAgent = requestHeaders[HttpHeaders.UserAgent] == null && content.headers[HttpHeaders.UserAgent] == null
    if (missingAgent && needUserAgent()) {
        block(HttpHeaders.UserAgent, KTOR_DEFAULT_USER_AGENT)
    }

Workaround Set User-Agent header for every request instead of setting it 1 time for the client

[dmitrievanthony]

Hi @dtolstyi, thanks for reporting! I’m working on it, but meanwhile, as a workaround, you could use UserAgent feature to set the user agent:

install(UserAgent) {
    agent = "Test Agent"
}

[dtolstyi]

I see. Thank you for your answer @dmitrievanthony. Should we use defaultRequest block to specify default headers using ktor infrastructure?