Can t you make the client of a testApplication follow redire

Question

Can t you make the client of a testApplication follow redirects

Aleksei Tirman [JB] · Answer

It s enabled by default The following test passes ``` Test fun test = testApplication application routing get redirect call respondRedirect get call respondText hello assertEquals hello client get redirect bodyAsText ```

ribesg · Answer

I did some more tests Your test passes in my environment Your test but modified to use Resources also passes But my actual test with the real application endpoints doesn t and I don t know why

ribesg · Answer

The endpoints ``` post lt V1 OldTimeSlots gt call respondRedirect application href V1 EventTimeSlots post lt V1 EventTimeSlots gt val response = EventTimeSlotsResponse call respond HttpStatusCode OK response ```

ribesg · Answer

2 identical tests the first one calling the new endpoint passes The second one calling the old one fails ``` Test fun `EventTimeSlots endpoint should return event timeslots` = testApplication val client = createClient install ContentNegotiation json install Resources val expectedResponse = EventTimeSlotsResponse val response = V1 EventTimeSlots contentType ContentType Application Json setBody body lt EventTimeSlotsResponse gt assertEquals expectedResponse response Test fun `OldTimeslots endpoint should still work` = testApplication val client = createClient install ContentNegotiation json install Resources val expectedResponse = EventTimeSlotsResponse val response = V1 OldTimeSlots contentType ContentType Application Json setBody body lt EventTimeSlotsResponse gt assertEquals expectedResponse response ```

ribesg · Answer

The error ```io ktor client call NoTransformationFoundException No transformation found class io ktor utils io ByteBufferChannel gt class blabla route EventTimeSlotsResponse with response from <http localhost v1 timeslots> status 302 Found response headers Location v1 event timeslots Date Wed 11 May 2022 15 01 33 GMT Server Ktor 2 0 1 Content Length 0```

Aleksei Tirman [JB] · Answer

Are you able to provide a sample project or describe specific conditions for reproduction Otherwise it s difficult to say what went wrong

ribesg · Answer

I need to make a test that reproduces the issue isolated from my actual app For now I didn t manage to reproduce it as I said your test but with Resources still worked I need to get closer to what I have

ribesg · Answer

< Aleksei Tirman JB > I finally have a reproducer I think the issue comes from having a request body it works without it ``` Resource a Serializable class A Resource b Serializable data class B val parent A = A Resource c Serializable data class C val parent B = B Serializable data class RequestBody val value Int Serializable data class ResponseBody val value Int Test fun `Should follow redirects` = testApplication val value = 1337 environment config = MapApplicationConfig module install CallLogging install DefaultHeaders install AutoHeadResponse install ServerContentNegotiation json install ServerResources routing post lt A B gt call respondRedirect application href A C post lt A C gt val requestBody = call receive lt RequestBody gt call respond HttpStatusCode OK ResponseBody requestBody value val client = createClient install ClientContentNegotiation json install ClientResources val result = A B contentType ContentType Application Json setBody RequestBody value body lt ResponseBody gt assertEquals value result value ```

Aleksei Tirman [JB] · Answer

The problem is that the `HttpRedirect` plugin redirects requests only with `GET` and `HEAD` methods by default You can disable checking HTTP method to make it work ```val client = createClient followRedirects = false install HttpRedirect checkHttpMethod = false install ClientContentNegotiation json install ClientResources ```

ribesg · Answer

Oh And why is that

Aleksei Tirman [JB] · Answer

I don t know There is this condition in the code ```if plugin checkHttpMethod amp amp origin request method in ALLOWED FOR REDIRECT return intercept origin ```

Aleksei Tirman [JB] · Answer

Where `ALLOWED FOR REDIRECT` is `setOf HttpMethod Get HttpMethod Head `

ribesg · Answer

Ok Weird I suppose we need to set `followRedirects` to false because it installs the `HttpRedirect` plugin with default config It s also weird to have to do that to modify the config

Aleksei Tirman [JB] · Answer

Yes

ribesg · Answer

With the redirect configuration added my test now passes I also need to change my Ktor Client configuration everywhere as not redirecting depending on method is quite unexpected Thanks

Aleksei Tirman [JB] · Answer

I think it s somehow related to the security

ribesg · Answer

Various RFCs changed what should be done when receiving a 301 302 regarding the method of the call now it looks like 307 308 were added to remove any ambiguity

ribesg · Answer

I read something about receiving a 301 302 when doing a PUT POST to update create a resource to redirect you to a page with the results where you should do a GET to get the page

ribesg · Answer

Yeah this method limitation was removed from the 2014 RFC <https datatracker ietf org doc html rfc7231 section 6 4 2>

ribesg · Answer

I think that the `checkHttpMethod` should apply only to old 301 and 302 codes and not 307 and 308 I m also gonna use 308 in my case