xai-org/x-algorithm · error

Not implemented: to_thrift for Action

Error message

Not implemented: to_thrift for Action

What it means

Action's MValCodec implementation is decode-only; calling to_thrift panics with an explicit 'not implemented' message. The type is meant to be read from Thrift responses, not written back.

Source

Thrown at visibility-filtering-client/models.rs:255

                        proto.read_field_end().unwrap();
                    }
                    proto.read_struct_end().unwrap();
                    if has_avoid {
                        result = Action::Avoid;
                    }
                }
                _ => {
                    proto.skip(field.field_type).unwrap();
                }
            }
            proto.read_field_end().unwrap();
        }
        proto.read_struct_end().unwrap();
        result
    }

    fn to_thrift(&self, _proto: &mut dyn TOutputProtocol) {
        panic!("Not implemented: to_thrift for Action")
    }
}

impl MValCodec for DropReason {
    fn thrift_type() -> TType {
        TType::Struct
    }

    fn from_thrift(proto: &mut dyn TInputProtocol) -> Self {
        proto.read_struct_begin().unwrap();
        loop {
            let field = proto.read_field_begin().unwrap();
            if field.field_type == TType::Stop {
                break;
            }
            proto.skip(field.field_type).unwrap();
            proto.read_field_end().unwrap();
        }

View on GitHub (pinned to 24c60942c5)

Solutions

  1. Do not serialize Action via this codec.
  2. Implement to_thrift by writing the same discriminators/tags the from_thrift reader consumes.
  3. Use the protobuf equivalent (vf_pb) if wire serialization is required.

Example fix

// before
fn to_thrift(&self, _proto: &mut dyn TOutputProtocol) {
    panic!("Not implemented: to_thrift for Action")
}

// after
fn to_thrift(&self, proto: &mut dyn TOutputProtocol) {
    // write the same tag/discriminator layout from_thrift parses
    proto.write_struct_begin(&TStructIdentifier::new("Action")).unwrap();
    /* field writes mirroring the reader */
    proto.write_field_stop().unwrap();
    proto.write_struct_end().unwrap();
}
Defensive patterns

Strategy: type-guard

Type guard

trait WriteCodec { fn to_thrift(&self, p: &mut dyn TOutputProtocol); }
// Action does not implement WriteCodec -> accidental encode fails at compile time

Try / catch

let r = std::panic::catch_unwind(|| a.to_thrift(proto));
if r.is_err() { /* skip field or use protobuf representation */ }

Prevention

When it happens

Trigger: Encoding an Action enum/struct via MValCodec::to_thrift — e.g. persisting it, sending it in a request, or a round-trip serialization test.

Common situations: Generic serializers that iterate all codec impls; new code forwarding Action values over Thrift; test utilities asserting encode/decode symmetry.

Related errors

AI-assisted analysis of xai-org/x-algorithm@24c60942c5 (2026-08-28). Data as JSON: /api/errors/41035907e64b7a89. Report an issue: GitHub.