[JAVA] Cannot generate API because of requestBody that contains $ref based on importMappings

Description

For some reason, I cannot generate my API because of the patch request described below. I played around with the definition and found out that the requestBody is the source of the problem.

The generation works if I put the $ref inside a list :

 requestBody:
        description: The object
        required: true
        content:
          application/json:
            schema:
              type: array
              items:
                $ref: "#/components/schemas/TestObject"
              minItems: 1

or if the $ref is on a component defined in the api.yml itself instead of an import mapping.

Swagger-codegen version

3.2.3 and tested with 3.3.3 and it does not work either.

Swagger declaration file content

...

patch:
      summary: Update a specific object
      operationId: updateObject
      parameters:
      - name: objectId
        in: path
        required: true
        description: object id
        schema:
          type: string
      requestBody:
        description: The object
        required: true
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/TestObject"
      responses:
        default:
          description: Updated object
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/TestObject"

....

Command line used for generation

Java, using the following gradle task, ran with Intellij :

openApiGenerate {
    generatorName = "spring"
    inputSpec = file("src/main/openapi/api.yml").toString()
    outputDir = file("${buildDir}/openapi-generated-code").toString()
    apiPackage = "com.test.api"
    modelPackage = "com.test.model"
    configOptions = [
        dateLibrary      : "java8",
        java8            : true,
        interfaceOnly    : true,
        serializableModel: true
    ]
    importMappings = [
        TestObject: "com.test.model.TestObject"
    ]
}

Start by reproducing the Spring generation from src/main/openapi/api.yml with the shown openApiGenerate Gradle configuration and importMappings. Trace how a requestBody schema containing a direct $ref is handled compared with the array case, then verify that generation succeeds and produces the expected API using the imported TestObject model.