Validate maps as records

[zyxw59]

This is necessary for resolving maps as records in unions.

[zyxw59]

The use case here is a REST server which receives JSON objects, converts them to avro based on a pre-existing schema, and sends them to a Kafka queue. The schema looks something like this:

{
  "name": "event",
  "type": "record",
  "fields": [
    {
      "name": "event_id",
      "doc": "unique uuid for the event",
      "type": "string"
    },
    {
      "name": "properties",
      "type": [
        "null",
        {
          "type": "record",
          "name": "Properties",
          "fields": [
            {
              "name": "tab",
              "type": "string"
            }
          ]
        }
      ],
      "default": null
    }
  ]
}

An example JSON object for this schema could be:

{
  "event_id": "3756d9d1-78b3-4c45-9190-d9ca9c523cb7",
  "properties": {
    "tab": "some tab name"
  }
}

When the JSON object is converted to Avro with avro_rs::types::Value::from, the properties field is represented as an Avro map. If the properties field in the schema were just a record, this would be fine, since Value::resolve already resolves maps as records (https://github.com/flavray/avro-rs/blob/main/src/types.rs#L682). But since the field is a union, it first has to resolve the union, which uses Value::validate to find the appropriate union variant. Since Value::validate does not accept a Value::Map for a Schema::Record, this fails, and the Avro object cannot be resolved with the schema.

More generally, I think there is the question of whether value.resolve(schema).is_ok() implies value.validate(schema) and vice-versa.

[flavray]

Got it! Thank you for the details! This looks good to me. 🙂