---
status: draft
last_updated: 2026-04-30
---

# Build & Distribution

Dependencies, project structure, tree-shaking, sub-path exports, and build targets.

## Dependencies

| Package | Type | Purpose |
|---------|------|---------|
| `@repeaterjs/repeater` | direct | Small (~3KB). Core async iterable primitive for `subscribe()`. |
| `ioredis` | peer (optional) | Redis client. Only imported by `event-target-redis.ts`. Type-only import at compile time. |
| `@rayhanadev/iroh` | peer (optional, future) | Iroh NAPI-RS binding. Only imported by `event-target-iroh.ts`. |

No other external dependencies. No logger dependency.

## Project Structure

```
@alkdev/pubsub/
  src/
    index.ts              # Barrel: re-exports core API
    types.ts              # TypedEvent, TypedEventTarget, etc.
    create_pubsub.ts      # createPubSub factory
    operators.ts          # filter, map, pipe
    event-target-redis.ts # createRedisEventTarget (peer dep: ioredis)
    # Future adapters (each is its own entry point + peer dep island):
    # event-target-websocket.ts  # peer dep: none (web standard)
    # event-target-iroh.ts       # peer dep: @rayhanadev/iroh
  test/
    create_pubsub.test.ts
    operators.test.ts
    event-target-redis.test.ts
    # event-target-websocket.test.ts
    # event-target-iroh.test.ts
  docs/
    architecture.md
    architecture/
    research/
  package.json
  tsconfig.json
  tsup.config.ts
  vitest.config.ts
```

## Sub-Path Exports

We use explicit sub-path exports rather than barrel-only + tree-shaking. Each adapter is importable by its own path:

```json
{
  "exports": {
    ".": { ... },
    "./event-target-redis": { ... },
    "./event-target-websocket": { ... },
    "./event-target-iroh": { ... }
  }
}
```

### Why Sub-Path Exports

- **Explicit** — doesn't rely on bundler tree-shaking behavior
- **Peer dep isolation** — `import from '@alkdev/pubsub/event-target-redis'` makes the dependency on ioredis explicit at the import site
- **Consistent with typemap pattern** — typemap's peer deps (zod, valibot, typebox) are each their own module; sub-path exports make this explicit at the package boundary

Sub-path entries are added as adapters are implemented. The barrel `index.ts` also re-exports everything for convenience — consumers who want tree-shaking can import from the barrel and rely on their bundler.

## Peer Dependencies

| Peer Dep | Required By | Optional |
|----------|-------------|----------|
| `ioredis@^5.0.0` | `event-target-redis` | Yes |
| `@rayhanadev/iroh` | `event-target-iroh` (future) | Yes |

Optional peer deps means `npm install @alkdev/pubsub` does NOT install ioredis or iroh. Consumers opt in by installing the peer dep and importing from the sub-path.

## Build

- **Tool**: `tsup` — produces dual ESM + CJS with declarations automatically
- **Entry points**: `src/index.ts`, `src/event-target-redis.ts`, plus future adapters
- **Format**: ESM + CJS
- **Target**: `es2022`
- **Splitting**: enabled (tsup code splitting for shared chunks)

```ts
// tsup.config.ts
import { defineConfig } from 'tsup';

export default defineConfig({
  entry: ['src/index.ts', 'src/event-target-redis.ts'],
  format: ['esm', 'cjs'],
  dts: true,
  sourcemap: true,
  clean: true,
  splitting: true,
  target: 'es2022',
});
```

## Testing

- **Runner**: `vitest` — matches taskgraph, natural fit with tsup/Node build pipeline
- **Config**: `vitest.config.ts` with `globals: true`

## Targets

- **Publish**: npm (`@alkdev/pubsub`)
- **Runtime**: Node 18+, Deno, Bun — pure JS (except iroh adapter which requires NAPI-RS)
- **Deno compatibility**: Source is standard TypeScript with no Deno-specific APIs. Deno can import from npm or JSR.