CRITICAL: Type registry not wired into stores — heterogeneous event deserialization broken #32

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Closed

opened 2026-02-20 00:21:20 +00:00 by ash · 0 comments

ash commented

2026-02-20 00:21:20 +00:00

Owner

Problem

EventStore[E] is generic with single type E. Stores deserialize directly into E via json.Unmarshal. This works for single-type streams but breaks for real-world heterogeneous event streams where one stream has OrderCreated, ItemAdded, OrderSubmitted, etc.

EventRegistry exists but is NOT integrated into the store read path. It's orphaned.

The Real Flow Needed

Append: serialize event data + store event type name (from registry or struct tag)
Load: read type name from store → registry.New(typeName) → deserialize into correct struct → return

Options

Option A: E is an interface

type OrderEvent interface { isOrderEvent() }
store := eskit.NewMemoryStore[OrderEvent](registry)

Store uses registry to deserialize. Loses some compile-time safety.

Option B: E is a sum type / tagged union

type OrderEvent struct {
    Type string
    OrderCreated *OrderCreated
    ItemAdded *ItemAdded
}

Store deserializes into envelope. Ugly but type-safe.

Option C: E is any, registry does everything

Like Rita/Myrra. Maximum flexibility, minimum type safety.

Recommendation

Option A with registry integration. The store constructor takes a Registry, uses it on Load. Event type name stored alongside data (already in headers for NATS, need column for SQLite/Postgres).

Must Fix

Wire EventRegistry into MemoryStore, SQLiteStore, PGStore, NATSStore
Store event type name on write
Use registry on read to create correct type
Conformance suite must test heterogeneous streams

Priority: CRITICAL

Without this, eskit can't handle real-world event streams.

## Problem EventStore[E] is generic with single type E. Stores deserialize directly into E via json.Unmarshal. This works for single-type streams but breaks for real-world heterogeneous event streams where one stream has OrderCreated, ItemAdded, OrderSubmitted, etc. EventRegistry exists but is NOT integrated into the store read path. It's orphaned. ## The Real Flow Needed 1. Append: serialize event data + store event type name (from registry or struct tag) 2. Load: read type name from store → registry.New(typeName) → deserialize into correct struct → return ## Options ### Option A: E is an interface ```go type OrderEvent interface { isOrderEvent() } store := eskit.NewMemoryStore[OrderEvent](registry) ``` Store uses registry to deserialize. Loses some compile-time safety. ### Option B: E is a sum type / tagged union ```go type OrderEvent struct { Type string OrderCreated *OrderCreated ItemAdded *ItemAdded } ``` Store deserializes into envelope. Ugly but type-safe. ### Option C: E is any, registry does everything Like Rita/Myrra. Maximum flexibility, minimum type safety. ### Recommendation Option A with registry integration. The store constructor takes a Registry, uses it on Load. Event type name stored alongside data (already in headers for NATS, need column for SQLite/Postgres). ## Must Fix - Wire EventRegistry into MemoryStore, SQLiteStore, PGStore, NATSStore - Store event type name on write - Use registry on read to create correct type - Conformance suite must test heterogeneous streams ## Priority: CRITICAL Without this, eskit can't handle real-world event streams.