panic when encoding array that can contain null values

[jgresty]

When trying to encode the data type:

type Data struct {
        Data *[]*string `json:"data"`
}

which is generated with avrogo from the schema

{
  "type": "record",
  "name": "Data",
  "namespace": "test",
  "connect.version": 1,
  "connect.name": "test.Data",
  "default": null,
  "fields": [
    {
      "name": "data",
      "default": null,
      "type": [
        "null",
        {
          "type": "array",
          "items": ["null", "string"]
        }
      ]
    }
  ]
}

results in the error:

panic: runtime error: index out of range [0] with length 0

goroutine 1 [running]:
github.com/heetch/avro.(*encoderBuilder).typeEncoder(0xc000137cc8, {0x539498?, 0xc00012e190?}, {0x53a0a0, 0x4eb000}, {{0x53a0a0, 0x4eb700}, {0x0, 0x0}, 0x0, ...})
	/home/jgresty/go/pkg/mod/github.com/heetch/avro@v0.4.4/encode.go:173 +0x190f
github.com/heetch/avro.(*encoderBuilder).typeEncoder(0xc000137cc8, {0x538e08?, 0xc0001282b8?}, {0x53a0a0, 0x4eb700}, {{0x53a0a0, 0x4eb700}, {0x0, 0x0}, 0x0, ...})
	/home/jgresty/go/pkg/mod/github.com/heetch/avro@v0.4.4/encode.go:208 +0xbd6
github.com/heetch/avro.(*encoderBuilder).typeEncoder(0xc000137cc8, {0x539498?, 0xc00012e1e0?}, {0x53a0a0, 0x4e8fc0}, {{0x53a0a0, 0x4e8fc0}, {0x4e63e1, 0x4}, 0x0, ...})
	/home/jgresty/go/pkg/mod/github.com/heetch/avro@v0.4.4/encode.go:176 +0x3c6
github.com/heetch/avro.(*encoderBuilder).typeEncoder(0xc000177cc8, {0x5393b8?, 0xc00011ca20?}, {0x53a0a0, 0x4f8640}, {{0x53a0a0, 0x4f8640}, {0x0, 0x0}, 0x0, ...})
	/home/jgresty/go/pkg/mod/github.com/heetch/avro@v0.4.4/encode.go:149 +0x15b6
github.com/heetch/avro.typeEncoder(0xc00012c120, {0x53a0a0?, 0x4f8640})
	/home/jgresty/go/pkg/mod/github.com/heetch/avro@v0.4.4/encode.go:71 +0x210
github.com/heetch/avro.marshalAppend(0xc000164100?, {0xc00016e000, 0x1, 0x64}, {0x4f8640?, 0x0?, 0x0?})
	/home/jgresty/go/pkg/mod/github.com/heetch/avro@v0.4.4/encode.go:38 +0xd3
github.com/heetch/avro.(*SingleEncoder).Marshal(0xc000164100, {0x538850, 0xc000120000}, {0x4f8640?, 0x0?})
	/home/jgresty/go/pkg/mod/github.com/heetch/avro@v0.4.4/singleencoder.go:64 +0x1ad
main.main()

I have a runnable example at: https://github.com/jgresty/avrotest

[skateinmars]

Hey @jgresty thanks a lot for opening that issue and especially for the code to reproduce this, and apologies for the delay in responding to this.
Unfortunately we do not have much bandwidth currently to work on this.

If you have control over the schema, I would suggest maybe wrapping the value in a record that has a nullable field?

{
  "type": "record",
  "name": "Data",
  "namespace": "test",
  "connect.version": 1,
  "connect.name": "test.Data",
  "default": null,
  "fields": [
    {
      "name": "data",
      "default": null,
      "type": [
        "null",
        {
          "type": "array",
          "items":{
                "name":"ArrayValue",
                "type":"record",
                "fields":[
                    {"name":"value", "type":["null", "string"]}
                ]
            }
        }
      ]
    }
  ]
}