Parse Kotlin metadata manually to honor nullability and avoid kotlin-metadata-jvm dep

[AidanLaing]

Version: 2.6.0-SNAPSHOT Exception: KotlinNullPointerException Message: Response from {path to my suspend fun...} was null but response body type was declared as non-null

The current structure of my suspend fun in my service interface:

@POST("api/...")
suspend fun request(@Body body: Body): Response?

I'm using Gson for serialization.

Is there a way to declare the response body type as nullable that I'm missing? I've tried adding null safety on my response object with ? and @Nullable with no success.

[JakeWharton]

Not currently. I'm working on a parser for Kotlin metadata so we don't have to depend on a gigantic jar to read one isNullable boolean.

On Thu, Apr 11, 2019, 8:27 PM Aidan Laing notifications@github.com wrote:

Version: 2.6.0-SNAPSHOT Exception: KotlinNullPointerException Message: Response from {path to my suspend fun...} was null but response body type was declared as non-null

The current structure of my suspend fun in my service interface:

@POST("api/...") suspend fun request(@Body body: Body): Response?

I'm using Gson for serialization.

Is there a way to declare the response body type as nullable that I'm missing? I've tried adding null safety on my response object with ? and @Nullable with no success.

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[rodion-m]

@JakeWharton Please notice that suspend ...: List<*> also is not supported. Version: 2.6.0-SNAPSHOT For instance: suspend fun fetchStrings(): List<String>

[JakeWharton]

I'm not sure how that's related to null body handling. Feel free to file a separate issue with a failing test case.

On Wed, Apr 17, 2019, 9:41 PM Rodion Mostovoy notifications@github.com wrote:

@JakeWharton https://github.com/JakeWharton Please notice that suspend ...: List<*> also is not supported. Version: 2.6.0-SNAPSHOT For instance: suspend fun fetchStrings(): List

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[wlara]

Added @JakeWharton I'm getting a similar KotlinNullPointerException using a service that returns 204 (no content) on a delete call. Something like this: @DELETE("/api/{id}") suspend fun deleteItem(@Path("id") id: String) Would that use case also be fixed as part of this issue?

[JakeWharton]

No. That's #2867

[Hospes]

Hi there! Any chance to get update on this issue? :) Want to move to 2.6.0 and remove all other dependencies but can't cause of null response body not supported :(

[jgavazzisp]

Moved to #2867

[JakeWharton]

That is not related to this issue. It's #2867.

[JavierSegoviaCordoba]

So at this moment we should force an exception with a interceptor for 204 responses?

[JakeWharton]

This issue has nothing to do with 204 handling and when it's fixed 204 handling won't have changed in any way. That's #2867.

[claucookie]

Just in case it helps. I was experiencing the exact same KotlinNPE issue over the last 2 days and after trying Converters and Adapters what really worked was to return Response<Unit> in the retrofit method declaration.

I use Retrofit 2.6.0.

[Pitel]

Any progress? We've just changed some of our REST endpoints to 204. So I thought it would be enought to just remove response type (making it Unit), but no.

Using Response<Unit> works :+1:

[vladimirfx]

Why not:

https://github.com/Kotlin/kotlinx.reflect.lite

[JakeWharton]

Because it doesn't provide the necessary info

[september669]

Using Response<Unit> works

In this case retrofit does not throw any exception when got 4xx codes Reproduced at 2.6.2

[JakeWharton]

That is the expected behavior for that return type.

[MiSikora]

Is it something that is open for a PR or do you want to implement it yourself in Retrofit or as an external project and use it here? I see that there is an old branch so I'd like to ask first before spending some time on it.

[JakeWharton]

Feel free to give it a shot

On Tue, Feb 25, 2020, at 5:31 AM, Michał Sikora wrote:

Is it something that is open for a PR or do you want to implement it yourself in Retrofit or as an external project and use it here? I see that there is an old branch https://github.com/square/retrofit/tree/jakew/nully/2019-02-15 so I'd like to ask first before spending some time on it.

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[RoarGronmo]

Found that empty response failed with the NPE mentioned. To cope with that problem, I wrapped all my backend json calls (on the backend side) inside an array. So if the result was empty, I returned an empty array at least.

Just a tip to solve the problem if you have access and ability to change your backend data source.

RG

[jemshit]

Using Response<Unit> works

In this case retrofit does not throw any exception when got 4xx codes Reproduced at 2.6.2

Hi, to handle empty response only choice seems like Response<Void> but that makes 4xx look like success. Any proper way to handle both empty response AND see 4xx as error (e.g. @GET suspend fun should throw exception) ?

Update: Using custom response converter suggested in #1554 works fine, (not converting empty body and returning null in such cases). But return type in API interface must be Unit instead of Any?. Otherwise it throws exception written above by OP

[magneticflux-]

https://github.com/square/retrofit/issues/3075#issuecomment-586156499

Why not:

https://github.com/Kotlin/kotlinx.reflect.lite

https://github.com/square/retrofit/issues/3075#issuecomment-586279157

Because it doesn't provide the necessary info

Are you sure? It looks to me like you can read "one isNullable boolean" right here: https://github.com/Kotlin/kotlinx.reflect.lite/blob/47bfb95540f361143add39300017c6904720812a/src/main/java/kotlinx/reflect/lite/api.kt#L45-L47

[klaszlo8207]

Any new on this?

How to handle 400 codes and empty body? I tried everything in this topic, but nothing worked.

Success called with the 400 error

[GiridharaSPK]

I have added wrong headers that caused me that HTTP 400 Bad request error.

removing the following worked .addHeader("Content-Encoding", "UTF-8") .header("Accept-Encoding", "identity")

  might help someone

[rezznov]

@JakeWharton not any updates about this? Its been 2 years since issue has open :D

[rezznov]

right now I handled this by a simple try catch like this

try {
                ResultWrapper.Success(request.invoke())
            } catch (e: KotlinNullPointerException) {
                ResultWrapper.NoContentError
            }

[LouisCAD]

Having an interceptor that rewrites the http 204 and 205 responses to 200 should work best.

[ferinagy]

Hi, I hit this a few times recently, so I thought I'd give it a shot: https://github.com/square/retrofit/pull/3544. Any feedback is welcome.

[Snailedlt]

If you get No type arguments expected for class Response when using Response<Unit>, make sure you're using retrofit2.Response<> and not something like okhttp3.Response. That fixed the issue for me

[tamimattafi]

If you get No type arguments expected for class Response when using Response<Unit>, make sure you're using retrofit2.Response<> and not something like okhttp3.Response. That fixed the issue for me

This saved me a lot of digging, was using a Response<T> class from my module

[MoustafaElsaghier]

any suggestion for flow?