[logbook-ktor-client] removes Content-Type request header

[grassehh]

Description

When sending requests using Ktor client with the LogbookClient plugin from logbook-ktor-client installed, the Content-Type header is removed from the request.
Another side effect of this issue is that JacksonJsonFieldBodyFilter does not work properly as it checks the content type.

Expected Behavior

The Content-Type header should be preserved when sending the request.

Actual Behavior

The Content-Typeheader is removed from the request.

Possible Fix

There are two places to fix.

• The first is in the LogbookClient class itself. This line should return

it

• The second place is in the ClientRequest class.
  The getHeaders() and getContentType() method should try to respectively append and retrieve the Content-Type header from the OutgoingContent.contentType property when applicable (this one is necessary in order for features like JacksonJsonFieldBodyFilter to work properly).
  Example:

override fun getHeaders(): HttpHeaders = HttpHeaders.of(request.headers.build().toMap())
        .also {
            if (it.contains(ContentType).not() && request.body is OutgoingContent) return it.update(
                ContentType,
                (request.body as OutgoingContent).contentType.toString()
            )
        }

override fun getContentType(): String? =
        request.contentType()?.toString()?.substringBefore(";") ?: (request.body as? OutgoingContent)?.contentType?.toString()

Explainations: For some reasons, Ktor removes the Content-Type header from the request object and pushes it into the OutgoingContent.
Thus the Content-Type is lost when Logbook replaces the content with a fresh new one by using ByteArrayContent(content), and the ClientRequest needs to retrieve the information from the OutgoingContent instead of the headers object.

Steps to Reproduce

• Checkout this repository: https://github.com/grassehh/issues
• Run the ClientTest test inside the zalando-logbook-1821 folder

The test will fail. If you uninstall LogbookClient, the test will pass.

Context

I was writing integration tests that check that my request contained the Content-Type: application/json header and it failed.

Your Environment

Ktor 2.3.10
Logbook 3.8.0

[kasmarian]

@grassehh please see #1833 with the fix that you suggested. And thank you very much for the detailed explanation of the issue and your investigation.

[kasmarian]

The fix will be in the next release, thank you for the detailed issue