Embedded properties missing from schema in 3.1.0 with JPA and spring-boot-data-rest

[obecker]

Describe the bug

We are running a Kotlin application with spring-boot-starter-data-rest and spring-boot-starter-data-jpa.
Spring Boot version 4.1.0
Springdoc version 3.1.0

Some entity classes have embedded properties. These properties are missing in the corresponding Open API schema definitions.

Example:

@Entity
class Person {

    @Id
    var id: Long? = null

    @Embedded
    var name: Name? = null
}

@Embeddable
class Name {
    var firstName: String? = null
    var lastName: String? = null
}

Springdoc 3.0.2 works as expected and generates

...
 "components": {
    "schemas": {
      "EntityModelPerson": {
        "type": "object",
        "properties": {
          "id": {
            "type": "integer",
            "format": "int64"
          },
          "links": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/Link"
            }
          },
          "name": {
            "$ref": "#/components/schemas/Name"
          }
        }
      },
...

With Springdoc 3.1.0 both name property and Name object schema are missing.
(Note: Springdoc 3.0.3 doesn't work because of #3263)

To Reproduce
See https://github.com/obecker/springdoc-issue-demo

Run the main function in SpringdocIssueDemoApplication and open http://localhost:8080/swagger-ui/index.html

Downgrade the springdoc version in build.gradle.kts to see the old behavior.

[Mattias-Sehlstedt]

Could be a duplicate of #3328 (as in the same cause but another symptom)?

[obecker]

Well, I'm not sure. I have initially seen the exception described in #3328, too, but could get rid of it by setting useHalAsDefaultJsonMediaType to false:

@Configuration
class SpringRestConfiguration : RepositoryRestConfigurer {
    override fun configureRepositoryRestConfiguration(config: RepositoryRestConfiguration, cors: CorsRegistry) {
        config.useHalAsDefaultJsonMediaType(false)
    }
}

[Mattias-Sehlstedt]

Well, I'm not sure. I have initially seen the exception described in #3328, too, but could get rid of it by setting useHalAsDefaultJsonMediaType to false:

@Configuration
class SpringRestConfiguration : RepositoryRestConfigurer {
    override fun configureRepositoryRestConfiguration(config: RepositoryRestConfiguration, cors: CorsRegistry) {
        config.useHalAsDefaultJsonMediaType(false)
    }
}

It could be that your configuration makes the processing not reach the unexpected nullpointer, but that it rather instead drops the embedded processors entirely and proceeds as if they were not even there in any sense (while the entire configuration is actually designed around them having to be there).

Is it possible to get HateoasProperties on the classpath easily without issue in your test application? That would be the easiest way to verify, since if it exists then the application correctly loads the needed configurations from SpringDocHateoasConfiguration.