Description

Currently, CBOR support in Fiber is implemented with direct imports of the github.com/fxamacker/cbor/v2 library, while the new MsgPack implementation (PR #3565) uses an opt-in pattern with binder mock functions to avoid forcing dependencies on rarely used serialization libraries.

Current State

CBOR (current implementation):

• Direct import of github.com/fxamacker/cbor/v2
• Uses cbor.Marshal and cbor.Unmarshal as defaults
• Forces dependency on all users

MsgPack (new pattern):

• Uses binder.UnimplementedMsgpackMarshal and binder.UnimplementedMsgpackUnmarshal as defaults
• Mock functions panic if called without explicit setup
• Allows users to opt-in by configuring their preferred MsgPack library

Proposed Changes

Refactor CBOR implementation to follow the MsgPack pattern:

1. Create binder.UnimplementedCborMarshal and binder.UnimplementedCborUnmarshal functions
2. Set these as defaults in the Config struct instead of cbor.Marshal/cbor.Unmarshal
3. Remove direct github.com/fxamacker/cbor/v2 import from core app
4. Update documentation to show users how to explicitly configure CBOR support
5. Maintain backward compatibility where possible

Benefits

• Reduces binary size for users who don't use CBOR
• Follows the opt-in philosophy for non-standard serialization formats
• Consistent approach across MsgPack and CBOR implementations
• Allows users to choose their preferred CBOR library

Context

This refactoring was discussed in PR #3565 (MsgPack implementation):

• PR: 🔥 feat: Add support for Msgpack #3565
• Comment: 🔥 feat: Add support for Msgpack #3565 (comment)

Related

• Part of the broader serialization architecture improvements
• Could be extended to other non-standard formats in the future
• Aligns with the plugin-based registry pattern discussion for Fiber v3