[JAVA] Retrofit2 Observable<Void> should be Observable<Response<Void>>

[zkdzegede]

Description

API calls that have no response content causes a null pointer in retrofit.

Null is not a valid element

This is currently what is produced:

  @POST("logout")
  Observable<Void> logout();

This causes the: Observable onNext to never be called

Swagger-codegen version

2.2.3

Swagger declaration file content or url

  /logout:
    post:
      operationId: logout
      responses:
        200:
          description: success
        401:
          description: 401

Command line used for generation

{
  "library": "retrofit2",
  "groupId": "com.test",
  "artifactVersion":"0.0.2",
  "invokerPackage": "com.test",
  "modelPackage": "com.test.model",
  "apiPackage": "com.test.api",
  "useRxJava2": true,
  "hideGenerationTimestamp": true
}

swagger-codegen generate -i doc/api/definitions/test.yaml -c doc/api/config/test.json -l java -o libs/api/test

Using:
Kotlin, Java, Retrofit2

Steps to reproduce

1. generate the api
2. subscribe to api.logout()

Related issues/PRs

---

Suggest a fix/enhancement

Swagger-codgen produces Observable<Void> when it should produce Observable<Response<Void>>

I found the solution here: https://stackoverflow.com/questions/41914037/rxjava2-retrofit2-handling-null-for-204-put-and-delete-requests

[zkdzegede]

I tested by manually overwriting with Observable<Response<Void>> and everything works as expected.

[jschoedt]

I think it would be more clean to use Completable as the return type although Response also works.

[zkdzegede]

@wing328 Any information on what swagger.yml response would lead to a Completable being generated?

Or is this not supported?

in RxJava2 Observable<Void> is an error [in RxJava2] but the swagger-codegen generates this...

[wing328]

@zkdzegede sorry for late reply on this. Please kindly try the latest stable release v2.3.0. If it's still an issue, we will look into it.

[zkdzegede]

It seems like v2.3.0 is not in brew...

[zkdzegede]

I just confirmed that this still happens in v2.3.0
@wing328

[wing328]

cc @bbdouglas @JFCote @sreeshas @jfiala @lukoyanov @cbornet

[wingsofovnia]

I confirm this still happens in v2.3.0 too. It's a really big problem because typical DELETE or any other endpoint that returns noting just doesn't work.

We should set Completable instead of Observable<Void> as @jschoedt proposed. I tested such replacement (Observable<Void> -> Completable), works as expected.

For those who generate client out of swagger defs directly during compile time, you may want use this dirty temporary hack (Gradle):

yourSwaggerGenTask.doLast {
    // Temporary fix https://github.com/swagger-api/swagger-codegen/issues/6553
    fileTree(dir: "$buildDir/yourSwaggerGenOutputFolder", include: '**/*Api.java').each {File file ->
        String apiContent = file.getText()
        apiContent = apiContent.replaceAll("Observable<Void>", "Completable")
        apiContent = apiContent.replaceAll("import io.reactivex.Observable;",
            "import io.reactivex.Observable;import io.reactivex.Completable;")
        file.write(apiContent)
    }
}

[cbornet]

The problem is that with Completable you lose response headers (typically the location header in a 201 created op)

[zkdzegede]

Even if temporary it seems better than the current situation which is an Error since RxJava2 Observables cannot contain Void.

I think Flowables can so would it be reasonable to change it to Flowable<Void> ?
I may be mistaken of course.