Serialize trait on ValidationState does not produce the expected output

[bcheidemann]

Hi,

I'm hoping to return the ValidationState struct from a Rust Node API using serde_wasm_bindgen. However, the struct does not serialize how I would expect it to.

println!("state = {state:#?}");
let json = serde_json::to_string(&state).unwrap();
println!("state (json) = {}", json);
let json = serde_json::to_string(&state.errors.get(0).unwrap()).unwrap();
println!("error (json) = {}", json);
let json = serde_json::to_string(&state.errors.get(0).unwrap().downcast::<OneOf>()).unwrap();
println!("error_downcast (json) = {}", json);

The above code produces the following output (formatted):

state = ValidationState {
  errors: [
      OneOf {
          path: "/jobs/example_job",
          states: [
              ValidationState {
                  errors: [
                      Required {
                          path: "/jobs/example_job/runs-on",
                      },
                  ],
                  missing: [],
                  replacement: None,
                  evaluated: {
                      "/jobs/example_job/steps/0",
                      "/jobs/example_job/steps/0/name",
                      "/jobs/example_job/steps",
                      "/jobs/example_job",
                      "/jobs/example_job/steps/0/with/submodules",
                      "/jobs/example_job/steps/0/uses",
                      "/jobs/example_job/steps/0/with",
                  },
              },
              ValidationState {
                  errors: [
                      Properties {
                          path: "/jobs/example_job",
                          detail: "Additional property 'steps' is not allowed",
                      },
                      Required {
                          path: "/jobs/example_job/uses",
                      },
                  ],
                  missing: [],
                  replacement: None,
                  evaluated: {
                      "/jobs/example_job",
                  },
              },
          ],
      },
  ],
  missing: [],
  replacement: None,
  evaluated: {
      "/on/pull_request/branches",
      "/on/pull_request",
      "/on/pull_request/branches/0",
      "/name",
      "/on",
      "",
      "/jobs",
  },
}

state (json) = {
  "errors": [
    {
      "code": "one_of",
      "path": "/jobs/example_job",
      "title": "OneOf conditions are not met"
    }
  ],
  "missing": []
}

error (json) = {
  "code": "one_of",
  "path": "/jobs/example_job",
  "title": "OneOf conditions are not met"
}

error_downcast (json) = {
  "code": "one_of",
  "path": "/jobs/example_job",
  "states": [
    {
      "errors": [
        {
          "code": "required",
          "path": "/jobs/example_job/runs-on",
          "title": "This property is required"
        }
      ],
      "missing": []
    },
    {
      "errors": [
        {
          "code": "properties",
          "detail": "Additional property 'steps' is not allowed",
          "path": "/jobs/example_job",
          "title": "Property conditions are not met"
        },
        {
          "code": "required",
          "path": "/jobs/example_job/uses",
          "title": "This property is required"
        }
      ],
      "missing": []
    }
  ],
  "title": "OneOf conditions are not met"
}

Note that the "states" field is missing from the serialized error unless it is downcast.

Is this the expected/intended behaviour?