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Declarative CBOR schema via annotations (CborId)

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
30/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
typescript
Domain
backend

Research direction

Start in CBOR.ts by reading the proposed CborId annotation types and codec engine design, then inspect the existing FromCDDL and CDDLSchema implementations for TransactionBody, TransactionWitnessSet, and Transaction. Done means converting all applicable modules, covering Tag-258 sets, redeemer map/array duality, nested maps, optional fields, and encoding preservation while maintaining backward compatibility.

Written by the indexing model from the issue text.

Description

enhancement exploration

Summary

Replace hand-written FromCDDL transforms with declarative schema annotations that describe CBOR wire format directly on Effect Schema types.

Motivation

Currently each module (TransactionBody, TransactionWitnessSet, Transaction, etc.) has:

  • A CDDLSchema (intermediate CBOR AST type)
  • A FromCDDL transform (hand-written 200-500 line encode/decode)
  • A FromCBORBytes that composes FromBytes with FromCDDL

This creates a two-hop pipeline (Uint8Array → CBOR AST → domain) with a validation boundary that clones objects and strips Symbol metadata (e.g. kEncoding for encoding preservation).

Proposal

A CborId Symbol annotation on Effect Schemas that carries CBOR layout metadata:

const CborId = Symbol.for("evolution/CborId")

const Address = Schema.Uint8ArrayFromSelf.annotations({
  [CborId]: { tag: 259 }
})

const Value = Schema.Struct({
  coin: Schema.BigIntFromSelf,
  multiasset: Schema.optional(MultiAsset),
}).annotations({
  [CborId]: { encoding: "array", fieldOrder: ["coin", "multiasset"] }
})

const TransactionOutput = Schema.Struct({
  address: Address,
  value: Value,
  datum: Schema.optional(Datum),
  scriptRef: Schema.optional(ScriptRef),
}).annotations({
  [CborId]: { encoding: "map", keys: { address: 0n, value: 1n, datum: 2n, scriptRef: 3n } }
})

A generic CBOR codec engine reads [CborId] annotations to:

  • Map struct fields to integer-keyed CBOR map entries or positional array slots
  • Wrap values in CBOR tags (e.g. #6.258 for sets)
  • Handle optional fields (omit from map when undefined)
  • Thread kEncoding preservation metadata automatically

Benefits

  • Eliminates FromCDDL — no hand-written encode/decode per module
  • Eliminates CDDLSchema — domain schema IS the codec schema, no intermediate type
  • Encoding preservation is free — single transform boundary, no clone/Symbol stripping
  • Self-documenting — annotations describe the wire format directly
  • Less code — TransactionBody goes from ~500 lines of transform to ~25 lines of annotated schema

Scope

  • Build CborId annotation types and codec engine in CBOR.ts (~200-400 lines)
  • Convert all modules with FromCDDL transforms to use annotated schemas
  • Handle edge cases: Tag-258 sets, redeemer map/array duality, nested maps, etc.
  • Maintain backward compatibility with existing domain types

Context

Discovered during CBOR encoding preservation work. The immediate fix (replacing MapFromSelf/Tuple CDDLSchemas with non-cloning Schema.declare) unblocks encoding preservation. This issue tracks the larger architectural improvement.

Dominant language
TypeScript
Stars
22
Forks
31
Avg merge
3d 4h
Merged PRs (30d)
27

Getting set up

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

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