Hacktoberfest 2026：メンテナが10月に向けて印を付けた、オープンで初心者向けの issue。 Hacktoberfest の issue を見る

EventJournal: after #7461, a custom journal cannot decode EventLog payloads with one union codec

クローズ
  • 何か問題がありますか？
#8,476 コメント 1 件 リアクション 0 件 担当者 0 名 GitHub で見る

メンテナーはふだん 1 日以内に返信

@Marve10s がすでに取り組んでいます。

2026年10月17日 から。

  • #9465 @Marve10s による — オープン

評価

難易度
4/5
見積もり時間
3〜5日
初心者へのやさしさ
55/100
issue の種類
バグ
明瞭さ
おおむね明確
活発さ
活発
技術スタック
typescript
領域
backend

調査の方向性

Run the supplied repro with bun repro.ts, then inspect the EventJournal.write and Entry.payload contracts alongside the #7461 changeset. Determine whether the documentation, migration note, or a group decoding helper best makes the per-event payloadSchemaBinary requirement explicit, and confirm the repro no longer leaves custom journals decoding payloads with an incompatible union codec.

索引モデルが issue の本文から書いたものです。

説明

What version of Effect is running?

effect 4.0.0-rc.117 (upgrading from 4.0.0-rc.112)

What steps can reproduce the bug?

A custom EventJournal receives write({ event, primaryKey, payload }) from EventLog and must decode payload itself, for example to validate the entry or to store it in its own format. On rc.112 the payload was MessagePack, which describes itself, so a journal could decode every event in a group with one codec built from the union of the payload schemas.

#7461 removed effect/unstable/encoding/Msgpack. The obvious port, Msgpack.schema(Union) → SchemaBinary.toCodec(Union), compiles and type-checks, but it rejects every payload that EventLog writes. SchemaBinary bytes follow the layout of the codec that wrote them, and EventLog writes each payload with its own event's payloadSchemaBinary, not with a codec for the union.

Minimal repro (both versions installed side by side):

{
  "type": "module",
  "dependencies": {
    "effect-old": "npm:[email protected]",
    "effect": "4.0.0-rc.117"
  }
}

import * as OldSchema from 'effect-old/Schema'
import * as OldMsgpack from 'effect-old/unstable/encoding/Msgpack'
import * as OldEventGroup from 'effect-old/unstable/eventlog/EventGroup'
import * as Schema from 'effect/Schema'
import * as SchemaBinary from 'effect/unstable/encoding/SchemaBinary'
import * as EventGroup from 'effect/unstable/eventlog/EventGroup'

const oldPayloads = [
  OldSchema.Struct({ name: OldSchema.Literal('user/create'), id: OldSchema.String }),
  OldSchema.Struct({ name: OldSchema.Literal('user/rename'), id: OldSchema.String, to: OldSchema.String })
] as const
const payloads = [
  Schema.Struct({ name: Schema.Literal('user/create'), id: Schema.String }),
  Schema.Struct({ name: Schema.Literal('user/rename'), id: Schema.String, to: Schema.String })
] as const

const OldGroup = OldEventGroup.empty
  .add({ tag: 'user/create', primaryKey: (p) => p.id, payload: oldPayloads[0] })
  .add({ tag: 'user/rename', primaryKey: (p) => p.id, payload: oldPayloads[1] })
const Group = EventGroup.empty
  .add({ tag: 'user/create', primaryKey: (p) => p.id, payload: payloads[0] })
  .add({ tag: 'user/rename', primaryKey: (p) => p.id, payload: payloads[1] })

const input = { name: 'user/rename', id: 'u1', to: 'Ada' } as const

// rc.112: EventLog writes event.payloadMsgPack bytes; one union codec decodes them.
const oldBytes = OldSchema.encodeSync(OldGroup.events['user/rename'].payloadMsgPack)(input)
console.log('rc.112 union decode:', OldSchema.decodeUnknownSync(OldMsgpack.schema(OldSchema.Union(oldPayloads)))(oldBytes))

// rc.117: EventLog writes event.payloadSchemaBinary bytes; the direct port of the same journal code fails.
const bytes = Schema.encodeSync(Group.events['user/rename'].payloadSchemaBinary)(input)
Schema.decodeUnknownSync(SchemaBinary.toCodec(Schema.Union(payloads)))(bytes)

Run it with bun repro.ts.

What is the expected behavior?

Either a journal can decode an EventLog payload without knowing which event wrote it, as on rc.112, or the API makes the per-event contract hard to miss.

What do you see instead?
rc.112 union decode: { name: "user/rename", id: "u1", to: "Ada" }
SchemaError(Missing key)

The union codec fails for every member of the union, not only for later ones. So every EventLog write through such a journal fails at runtime, and nothing in the types warns about it. The fix is to look up group.events[tag].payloadSchemaBinary for each entry, but nothing in the EventJournal docs or the #7461 changeset points to it.

Additional information

Possible fixes, from smallest to largest:

  1. Document on EventJournal.write and Entry.payload that the bytes are encoded with the writing event's payloadSchemaBinary, so a reader must decode them with that same codec.
  2. Add a migration note to the #7461 changeset: SchemaBinary.toCodec(schema) is not a drop-in replacement for Msgpack.schema(schema) when the reader's schema differs from the writer's, for example a union reading a member's bytes.
  3. Export a helper that decodes an entry for a group, for example EventGroup.decodePayload(group, entry), so custom journals do not have to write their own lookup by tag.
主要言語
TypeScript
スター
16.7k
フォーク
808
平均マージ
10時間 15分
マージ済み PR（30日）
845

環境構築

このプロジェクトには開発コンテナ、Dockerfile、コントリビューションガイドがありません。まず README を読み、一般的な手順ははじめてのコントリビューションガイドを参照してください。

はじめの一歩

  1. issue を最後まで読み、次にプロジェクトのコントリビューションガイドを読みます。
  2. 着手することを issue にコメントします — 二人が同じ作業をするのを防げます。
  3. リポジトリをフォークし、ブランチを切って変更します。
  4. issue 番号を参照したプルリクエストを送ります。

Effect-TS/effect のほかの issue

Effect-TS/effect の issue をすべて見る

似ている issue

TypeScript の issue をもっと見る

新しい issue をメールで受け取る

初心者向けの GitHub issue を短くまとめたダイジェスト。