Kotlin value classes get an incorrect name

[serandel]

Describe the bug

Springdoc is putting a random (?) suffix to the end of my fields when they're a Kotlin value class.

This is my DTO for this example:

@Serializable
data class Address(
    val streetName: String? = null,
    val postalCode: String? = null,
    val town: String? = null,
    val country: Country,
)

@JvmInline
@Serializable
value class Country(val isoCode: String)

Please, bear in mind that the other properties should also be value classes. I don't have it this way yet because I was researching this issue.

The problem is that when a schema is generated through

@Operation(summary = "foobar")
fun fooBar(
    @Parameter(schema = Schema(implementation = Address::class))
    address: Address
)

the country field is documented as being called country-GvCqL24, which is just wrong.

I've tested that KotlinX Serialization (which we're using instead of Jackson) is correctly defining the field name as country in the Json objects.

To Reproduce Steps to reproduce the behavior:

• Spring Boot: 3.2.3
• SpringDoc: org.springdoc:springdoc-openapi-starter-webmvc-ui 2.5.0
• Expected description:

    "Address": {
      "type": "object",
      "properties": {
        "streetName": {
          "type": "string"
        },
        "postalCode": {
          "type": "string"
        },
        "town": {
          "type": "string"
        },
        "country": {
          "type": "string"
        }
      }
    },

• Actual description:

    "Address": {
      "type": "object",
      "properties": {
        "streetName": {
          "type": "string"
        },
        "postalCode": {
          "type": "string"
        },
        "town": {
          "type": "string"
        },
        "country-GvCqL24": {
          "type": "string"
        }
      }
    },

• Sample code: see above

Expected behavior

The field should be named as the field is in the enclosing object, in this case: "country". That it is a value class for better domain modelling in my Kotlin service should be irrelevant. (The type is already being translated to string, which is right, it's only the name what's being garbled.)

Screenshots

Here we can see the wrong name being generated.

Additional context

This is a sample object when serialized from my controller:

{
    "streetName":"Main St",
    "postalCode":"12345",
    "town":"Smallville",
    "country":"US"
}

[bnasslahsen]

@serandel,

Not reproducible. Feel free to provide a Minimal, Reproducible Example - with HelloController that reproduces the problem.

This ticket will be closed, but can be reopened if your provide the reproducible sample.

[serandel]

Hi, @bnasslahsen , reopening this issue with a PoC in a repo, as asked.

https://github.com/serandel/springdoc-bug-poc

While doing this I realized the problem does not happen when we use Jackson to serialize the types, but just when changing to KotlinX Serialization. If you look at my repo, the first commit works, and then the second doesn't.

[serandel]

(Well, asking for the issue to be reopened, of course. :D)

[serandel]

{
  "openapi": "3.0.1",
  "info": {
    "title": "Foo API",
    "version": "v1"
  },
  "servers": [
    {
      "url": "http://localhost:8080",
      "description": "Generated server url"
    }
  ],
  "tags": [
    {
      "name": "Foo",
      "description": "Foo operations"
    }
  ],
  "paths": {
    "/foo/": {
      "post": {
        "tags": [
          "Foo"
        ],
        "summary": "Post a foo",
        "operationId": "postFoo",
        "parameters": [
          {
            "name": "foo",
            "in": "query",
            "required": true,
            "schema": {
              "$ref": "#/components/schemas/Foo"
            }
          }
        ],
        "responses": {
          "204": {
            "description": "Foo posted"
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "Foo": {
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "format": "uuid"
          },
          "bar-kCuQ4ew": {
            "type": "string"
          }
        }
      }
    }
  }
}

with bar-kCuQ4ew being the problem here.

[bnasslahsen]

@serandel,

There is an important Note in the docs you are missing: https://springdoc.org/#kotlin-support

If you add, that should work better:

implementation("com.fasterxml.jackson.module:jackson-module-kotlin") 

[serandel]

Yes, I had missed that indeed. Good catch! Thanks a lot!

Now I just have to ask... would it be feasible and reasonable to ask, as a feature request, to not depend on Jackson and also work with KotlinX Serialization?

[bnasslahsen]

@serandel,

If you are having better proposal than jackson-module-kotlin and willing to submit a PR, we can have look to it!