Auto Register Union Types

[Khalid-Nowaf]

After using Avrogen, I noticed my union types (more than two complex types ) become an "any" type, which I must manually register them explicitly (I got more than 20 types in my app).

Is there any way to register them implicitly? For example, parsing the schema should register them for me.

[nrwiersma]

How would that function? How would parsing the schema know what object implements it? What happens when there are multiple objects that implement the same schema for different situations?

[Khalid-Nowaf]

Once, I was trying to solve #284 (comment)

I added the following code to the decode/encode function (it is just a hack, but I believe there is a better way)

package schema

import (
	"bytes"

	"github.com/hamba/avro/v2"
)

type InfoType struct {
	Name string `avro:"name"`
	ID   int64  `avro:"id"`
}

type LocType struct {
	Latitude  int64 `avro:"latitude"`
	Longitude int64 `avro:"longitude"`
	Altitude  int64 `avro:"altitude"`
}

type MetaType struct {
	Priority int `avro:"priority"`
	Weight   int `avro:"weight"`
}

type Device struct {
	RecordA any `avro:"RecordA"`
	RecordB any `avro:"RecordB"`
	RecordC any `avro:"RecordC"`
}

func DeviceDecoder() func([]byte) (*Device, error) {
	schema := `{"name":"some.org.device.Device","type":"record","fields":[{"name":"RecordA","type":[{"name":"some.org.device.InfoType","type":"record","fields":[{"name":"name","type":"string"},{"name":"id","type":"long"}]},{"name":"some.org.device.LocType","type":"record","fields":[{"name":"latitude","type":"long"},{"name":"longitude","type":"long"},{"name":"altitude","type":"long"}]},{"name":"some.org.device.MetaType","type":"record","fields":[{"name":"priority","type":"int"},{"name":"weight","type":"int"}]}]},{"name":"RecordB","type":["some.org.device.InfoType","some.org.device.LocType","some.org.device.MetaType"]},{"name":"RecordC","type":[null,"some.org.device.InfoType","some.org.device.LocType","some.org.device.MetaType"]}]}`

	// the generator should have the full name of the type, and also the implementation, so it could inject such code
	avro.Register("some.org.device.InfoType", &InfoType{})
	avro.Register("some.org.device.LocType", &LocType{})
	avro.Register("some.org.device.MetaType", &MetaType{})

	r := bytes.NewReader([]byte{})

	decoder, err := avro.NewDecoder(schema, r)
	if err != nil {
		panic(err)
	}

	return func(encoded []byte) (*Device, error) {
		decoded := &Device{}
		r.Reset(encoded)
		if err := decoder.Decode(decoded); err != nil {
			return nil, err
		}
		return decoded, nil

	}
}

func DeviceEncoder() func(*Device) ([]byte, error) {
	schema := `{"name":"some.org.device.Device","type":"record","fields":[{"name":"RecordA","type":[{"name":"some.org.device.InfoType","type":"record","fields":[{"name":"name","type":"string"},{"name":"id","type":"long"}]},{"name":"some.org.device.LocType","type":"record","fields":[{"name":"latitude","type":"long"},{"name":"longitude","type":"long"},{"name":"altitude","type":"long"}]},{"name":"some.org.device.MetaType","type":"record","fields":[{"name":"priority","type":"int"},{"name":"weight","type":"int"}]}]},{"name":"RecordB","type":["some.org.device.InfoType","some.org.device.LocType","some.org.device.MetaType"]},{"name":"RecordC","type":[null,"some.org.device.InfoType","some.org.device.LocType","some.org.device.MetaType"]}]}`

	// the generator should have the full name of the type, and also the implementation, so it could inject such code
	avro.Register("some.org.device.InfoType", &InfoType{})
	avro.Register("some.org.device.LocType", &LocType{})
	avro.Register("some.org.device.MetaType", &MetaType{})

	w := bytes.NewBuffer([]byte{})

	encoder, err := avro.NewEncoder(schema, w)
	if err != nil {
		panic(err)
	}

	return func(decoded *Device) ([]byte, error) {
		w.Reset()
		if err = encoder.Encode(decoded); err != nil {
			return nil, err
		}
		return w.Bytes(), nil
	}

}

Also if the decoder/encoder is not needed, the function can like the following:

func getDeviceSchema() avro.Schema {
	schema := `{"name":"some.org.device.Device","type":"record","fields":[{"name":"RecordA","type":[{"name":"some.org.device.InfoType","type":"record","fields":[{"name":"name","type":"string"},{"name":"id","type":"long"}]},{"name":"some.org.device.LocType","type":"record","fields":[{"name":"latitude","type":"long"},{"name":"longitude","type":"long"},{"name":"altitude","type":"long"}]},{"name":"some.org.device.MetaType","type":"record","fields":[{"name":"priority","type":"int"},{"name":"weight","type":"int"}]}]},{"name":"RecordB","type":["some.org.device.InfoType","some.org.device.LocType","some.org.device.MetaType"]},{"name":"RecordC","type":[null,"some.org.device.InfoType","some.org.device.LocType","some.org.device.MetaType"]}]}`

	// the generator should have the full name of the type, and also the implementation, it could inject such code
	avro.Register("some.org.device.InfoType", &InfoType{})
	avro.Register("some.org.device.LocType", &LocType{})
	avro.Register("some.org.device.MetaType", &MetaType{})

	return avro.MustParse(schema)
}