[sudorandom]

The buf CLI can do this.

Here's how it looks to convert from encoded protobuf to json (protojson).

  buf convert schema.proto \
    --type YourMessageName \
    --from payload.binpb \
    --to output.json

And just invert the arguments to convert back.

  buf convert schema.proto \
    --type YourMessageName \
    --from data.json \
    --to encoded.binpb