problem-details-ktor-client-xml

Ktor Client integration for the Appendix B XML form: turn a recognized application/problem+xml error response into the same io.github.ilyankin.rfc9457.ProblemException that application code throws on the server side and problem-details-ktor answers.

Registering the XML codec is what pulls in an XML parser, exactly as on the server: an application that only ever decodes JSON depends on problem-details-ktor-client alone and never resolves xmlutil.

Both formats

val client = HttpClient(CIO) {
    expectSuccess = true
    HttpResponseValidator {
        problemJson()
        problemXml()
    }
}

Order does not matter here, unlike the server's ContentNegotiation pair, where whichever converter is registered first wins an absent or wildcard Accept. These two gate on Content-Type instead, and the two types they match are disjoint, so neither can shadow the other. Pinned in both directions by RegistrationOrderTest.

expectSuccess = true is required for the same reason as on the JSON side: without it Ktor throws nothing for a non-2xx response, so there is no exception to intercept and replace.