Jackson module scala potentially breaks serialization for swagger Model

[nick-benoit14]

Hello, running into a bit of a weird case here. Our project is in scala, but I have reproduced minimally with the code below. When I run the following

`
ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new DefaultScalaModule());

    Model model = new ModelImpl();

    Property property = new IntegerProperty();

    Map<String, Property> map = new HashMap<String, Property>();
    map.put("foo", property);
    model.setProperties(map);
    System.out.println(mapper.writeValueAsString(model));

`

I end up with the following exception com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Direct self-reference leading to cycle

When I remove

mapper.registerModule(new DefaultScalaModule());

Things deserialize as I would expect. It could be that I have something misconfigured somewhere, but I am surprised that the inclusion of the DefaultScalaModule makes a difference as ModelImpl is not a scala collection or class. More details on ModelImpl: https://www.javadoc.io/doc/io.swagger/swagger-models/1.5.13/io/swagger/models/ModelImpl.html

Any thoughts?

From my minimal example:
compile "io.dropwizard:dropwizard-jackson:2.0.10" compile "io.swagger:swagger-jersey2-jaxrs:1.5.13" compile "com.fasterxml.jackson.module:jackson-module-scala_2.12:+"

[pjfanning]

swagger 1.5 is compiled with an older version of jackson and is very dependent on using the version that appears in its dependency list - arbitrarily updating jackson to latest version does not work - if you update both jackson and swagger, you'll find latest version of swagger is built with latest version of jackson

https://mvnrepository.com/artifact/io.swagger/swagger-jaxrs/1.5.23 -- depends on jackson 2.9.9
https://mvnrepository.com/artifact/io.swagger/swagger-jaxrs/1.6.1 -- depends on jackson 2.10.1
https://mvnrepository.com/artifact/io.swagger/swagger-jaxrs/1.6.2 -- depends on jackson 2.11.1

[nick-benoit14]

That did it! I would have had a very hard time finding that out on my own. Thanks!

[nick-benoit14]

@pjfanning I did a bit more poking around. It seems I am able to use other versions of jackson, but I still run into the error depending on my version of jackson-module-scala. Here is my build.gradle

plugins {
    id 'java'
}

group 'jackson-test-3'
version '1.0-SNAPSHOT'

sourceCompatibility = 1.8

repositories {
    mavenCentral()
}

dependencies {
    testCompile group: 'junit', name: 'junit', version: '4.12'
    compile "com.fasterxml.jackson.core:jackson-annotations:2.10.4"
    compile "com.fasterxml.jackson.core:jackson-core:2.10.4"
    compile "com.fasterxml.jackson.core:jackson-databind:2.10.4"
    
    compile "io.swagger:swagger-jaxrs:1.6.1"
    compile "com.fasterxml.jackson.module:jackson-module-scala_2.12:2.10.1" // This works
    /*This works*/ // compile "com.fasterxml.jackson.module:jackson-module-scala_2.12:2.10.2"
    /* This does not work*/ // compile "com.fasterxml.jackson.module:jackson-module-scala_2.12:2.10.3"
    /* This does not work*/ // compile "com.fasterxml.jackson.module:jackson-module-scala_2.12:2.10.4"
}

Does it even make sense to you that jackson-module-scala would come into play serializing a non scala collection?

[pjfanning]

similar issue - swagger-akka-http/swagger-akka-http#171 - but I was able to code around that problem

[pjfanning]

I added a test case to the 2.11 branch that reproduces the problem (SwaggerTest) - still need to find time to debug why adding the DefaultScalaModule makes the code fail

[pjfanning]

I have added a hacky fix in 2.11 branch, targeted for 2.11.2 release. I modified the code to get the jackson scala module to ignore the swagger model classes. I hope I can find a better solution but this will do as a transitional fix.