signaltree-schema

Using @signaltree/schema

Enhancer for schema-driven validation. Register StandardSchema-compatible schemas (Zod / Valibot / ArkType / Effect Schema / any StandardSchemaV1) against dotted leaf paths; read errors per path or in aggregate. Observe-only: never blocks writes. Async-first with a write-sequence guard that drops stale verdicts.

Install:

npm install @signaltree/schema @signaltree/core @standard-schema/spec
npm install zod   # or valibot, arktype, etc.

Peer: @signaltree/core ^9, @standard-schema/spec ^1, @angular/core ^20 || ^21.

Basic — sync leaf schemas

import { signalTree } from '@signaltree/core';
import { schemas } from '@signaltree/schema';
import { z } from 'zod';

interface State {
  user: { email: string; age: number };
}

const tree = signalTree<State>({ user: { email: '', age: 0 } }).with(
  schemas({
    schemas: {
      'user.email': z.string().email(),
      'user.age': z.number().int().min(0),
    },
  })
);

tree.$.user.email.set('not-an-email');
tree.schemas.errorsAt('user.email')(); // 'Invalid email'
tree.schemas.isValid(); // false

Async schemas — pending state + write-sequence guard

import { z } from 'zod';

const usernameSchema = z.string().refine(
  async (value) => {
    const r = await fetch(`/api/check-username?u=${value}`);
    return (await r.json()).available;
  },
  { message: 'Username taken' }
);

const tree = signalTree({ user: { username: '' } }).with(schemas({ schemas: { 'user.username': usernameSchema } }));

tree.$.user.username.set('jonathan');
tree.schemas.isPendingAt('user.username')(); // true (in flight)
// On settle:
tree.schemas.errorsAt('user.username')(); // null or 'Username taken'

The write-sequence guard drops stale verdicts. If a newer write arrives mid-flight, the older schema run is orphaned — its promise still resolves (we can't abort it), but its verdict is discarded.

Debounce validate() for I/O-bound schemas. Calling validate() per keystroke piles up orphaned network requests. Wrap in a debounce.