Serialization that works with Json codec does not work with protobuf

[vigoo]

ISSUE

This is in fact (very likely) a zio-schema issue, but it is reproducible with zio-flow tests.
Serialization of remote values in zio-flow is implemented using zio-schema. The library defines the schema of all the remote types we have, and the actual serialization is the responsibility of a zio-schema codec. This allows us to switch between different serialization formats without implementing codecs for them one by one.

There is a test suite that performs roundtrip serialization tests for all the supported zio-flow remote types: serializing with a given codec, then reading back and comparing the result with the original value.

The issue is that this test passes with the JSON codec, but fails with protobuf.

SOLUTION

Solving this issue requires debugging the protobuf implementation in zio-schema, comparing it with the JSON codec. Ideally the fix would be in zio-schema with a test reproducing the issue there. If that works you can also enable the roundtrip serialization tests in zio-flow for the protobuf codec.

IMPACT

Fixing this problem is potentially a fix for all libraries that want to serialize with zio-schema using the protobuf codec.

WHERE TO LOOK

• To reproduce the issue, uncomment this line: https://github.com/zio/zio-flow/blob/main/zio-flow/shared/src/test/scala/zio/flow/serialization/RemoteSerializationSpec.scala#L18
• The actual problem is most likely in this implementation: https://github.com/zio/zio-schema/blob/main/zio-schema-protobuf/shared/src/main/scala/zio/schema/codec/ProtobufCodec.scala

[petoalbert]

I can check this.