Bean Validation on 'double' Nested Fields doesn't work

[LeeJaeDoo]

I'm trying to use ConstrainedFields for Bean Validation but unable to get it to work.

testImplementation("com.epages:restdocs-api-spec-mockmvc:0.16.2")

As you can see below, WorkflowDefinitionRequest has property SwitchBackBucketGroupParams[].SwitchBackBucketParams[].activity and it should not be null.

@Getter
@NoArgsConstructor
public class WorkflowDefinitionRequest {

    @NotBlank
    private String name;
    private String defDescription;

    @Valid
    @NotEmpty
    private List<SwitchBackBucketGroupParams> switchBackBucketGroupList;
}

@Getter
@NoArgsConstructor
public class SwitchBackBucketGroupParams {

    @NotNull
    private BucketType bucketType;

    private String description;

    @Valid
    @NotEmpty
    private List<SwitchBackBucketParams> switchBackBucketList;

}

@Getter
@NoArgsConstructor
public class SwitchBackBucketParams {

    @Valid
    @NotNull
    private ExperimentalActivityParams activity;

}

@Getter
@NoArgsConstructor
public class ExperimentalActivityParams {

    @NotBlank
    private String name;

    private String description;

    @NotNull
    private ActivityType type;
}

    @Test
    void createWorkflowDefinition() throws Exception {
        given(workflowService.registerWorkflow(any())).willReturn(1L);
        ConstrainedFields constrainedFields = new ConstrainedFields(WorkflowDefinitionRequest.class);

        this.mockMvc
            .perform(RestDocumentationRequestBuilders.post(URL_WORKFLOW)
                                                     .contentType(APPLICATION_JSON)
                                                     .content(readJson("workflowDefinitionRequest.json")))
            .andExpect(status().isCreated())
            .andDo(document("create-workflow-definition",
                            resource(ResourceSnippetParameters.builder()
                                         .description("create test")
                                         .requestSchema(Schema.schema("workflow create request"))
                                         .responseSchema(Schema.schema("201 response"))
                                         .tag(TAG_WORKFLOW_BUILD)
                                         .requestFields(constrainedFields.withPath("name").type(JsonFieldType.STRING).description("name"),
            constrainedFields.withPath("description").type(JsonFieldType.STRING).optional().description("description"),
            constrainedFields.withPath("switchBackBucketGroupList").type(JsonFieldType.ARRAY).description("bucket group"),
            constrainedFields.withMappedPath("switchBackBucketGroupList[].bucketType", 
"switchBackBucketGroupList").type(JsonFieldType.STRING).description("type of bucket group"),
constrainedFields.withMappedPath("switchBackBucketGroupList[].description", "switchBackBucketGroupList").type(JsonFieldType.STRING).optional().description("description of bucket group"),
            constrainedFields.withMappedPath("switchBackBucketGroupList[].switchBackBucketList", "switchBackBucketGroupList").type(JsonFieldType.ARRAY).description("bucket list of bucket group"),
            constrainedFields.withMappedPath("switchBackBucketGroupList[].switchBackBucketList[].activity", "switchBackBucketGroupList[].switchBackBucketList[]").type(JsonFieldType.OBJECT).description("activity of bucket list"),
            constrainedFields.withMappedPath("switchBackBucketGroupList[].switchBackBucketList[].activity.name", "switchBackBucketGroupList[].switchBackBucketList[].activity").type(JsonFieldType.STRING).optional().description("name of activity"),
            constrainedFields.withMappedPath("switchBackBucketGroupList[].switchBackBucketList[].activity.description", "switchBackBucketGroupList[].switchBackBucketList[].activity").type(JsonFieldType.STRING).optional().description("description of activity"),
            constrainedFields.withMappedPath("switchBackBucketGroupList[].switchBackBucketList[].activity.type", "switchBackBucketGroupList[].switchBackBucketList[].activity").type(JsonFieldType.STRING).description("type of activity")
                                                              .build())));
}

Generated openapi-3.0.yml file. As you can see below, author should be required but it doesn't show up in the required fields.

components:
  schemas:
    workflow create request:
      title: workflow create request
      required:
      - name
      - switchBackBucketGroupList
      type: object
      properties:
        name:
          minLength: 1
          type: string
          description: name
        defDescription:
          type: string
          description: definition description
        switchBackBucketGroupList:
          type: array
          description: bucket group
          items:
            required:
            - bucketType
            - description     // 'switchBackBucketGroupList' is a required object, 'switchBackBucketGroupList.description' is not a required field, but 'switchBackBucketGroupList.description' is exposed as a required field
            - switchBackBucketList
            type: object
            properties:
              switchBackBucketList:
                type: array
                description: bucket list of bucket group
                items:
                // 'required' not exposed
                  type: object
                  properties:
                    activity:
                      type: object
                      properties:
                        description:
                          type: string
                          description: description of activity
                        type:
                          type: string
                          description: type of activity
                        name:
                          type: string
                          description: name of activity
                      description: activity of bucket list

(+ Required is marked on property other than required within the marked object)

Is it a bug or am I missing something?