Complex object Select field, no reasonable defaultValue, and validation

            <form.AppField
              name="model"
              validators={{
                onBlur: equipmentFormDataSchema().shape.model,  // this doesn't type check
              }}
              children={(field) => {
                return <field.ModelSelectorField label="Model" />;
              }}
            />

// A "selectable object" is a schema for fields that are populated as a subschema
// object by a Select; in this case, we don't want all of the subschema errors,
// we just want to know when a selection got skipped.
const selectableObject = <T extends z.ZodTypeAny>(schema: T, message: string) =>
  schema
    .optional()
    .catch(undefined)
    .refine((x) => !!x, { message });

const equipmentFormDataSchema = (
  required_error: string = "Equipment selection is required",
) =>
  z.object(
    {
      serialNumberOrVIN: z
        .string({ required_error: "Serial number or VIN is required" })
        .nonempty("Serial number or VIN is required"),
      plateNumber: z.string().nullish(),
      carNumber: z.string().nullish(),
      notes: z.string().nullish(),
      model: selectableObject(equipmentModelFormDataSchema(), "Model selection is required"),
      customer: selectableObject(customerFormDataSchema(), "Customer selection is required"),
    },
    { required_error },
  );