@schemashift/io-ts-effect

io-ts → Effect Schema transformer for SchemaShift. Migrates io-ts codecs to their Effect Schema equivalents — the official successor to io-ts after fp-ts merged into Effect.


Tier: Pro+

Installation

``bash
npm install @schemashift/io-ts-effect
`

Usage

`typescript
import { createIoTsToEffectHandler } from '@schemashift/io-ts-effect';
import { TransformEngine } from '@schemashift/core';

const engine = new TransformEngine();
engine.registerHandler('io-ts', 'effect', createIoTsToEffectHandler());
`

Why This Migration Path?

- io-ts is deprecated — fp-ts merged into Effect-TS
- Effect Schema is the official successor for FP-oriented validation
- Same philosophy — both use branded types, codecs, and composable validation
- Better DX — Effect Schema has simpler API with better TypeScript inference

Transformation Mappings

$3

| io-ts | Effect Schema |
|-------|---------------|
| import * as t from 'io-ts' | import { Schema as S } from '@effect/schema' |
| import { pipe } from 'fp-ts/function' | import { pipe } from 'effect/Function' |

$3

| io-ts | Effect Schema |
|-------|---------------|
| t.string | S.String |
| t.number | S.Number |
| t.boolean | S.Boolean |
| t.bigint | S.BigInt |
| t.unknown | S.Unknown |
| t.never | S.Never |
| t.null | S.Null |
| t.undefined | S.Undefined |
| t.void | S.Void |

$3

| io-ts | Effect Schema |
|-------|---------------|
| t.type({...}) | S.Struct({...}) |
| t.partial({...}) | S.partial(S.Struct({...})) |
| t.array(X) | S.Array(X) |
| t.record(K, V) | S.Record(K, V) |
| t.union([A, B]) | S.Union(A, B) |
| t.tuple([A, B]) | S.Tuple(A, B) |
| t.literal(X) | S.Literal(X) |

$3

| io-ts | Effect Schema |
|-------|---------------|
| t.TypeOf | S.Schema.Type |
| t.OutputOf | S.Schema.Type |
| t.InputOf | S.Schema.Encoded |

Patterns Requiring Manual Review

$3

`typescript
// io-ts
const result = schema.decode(input);

// Effect Schema
const result = S.decodeUnknownSync(schema)(input);
// or for Either result:
const result = S.decodeUnknownEither(schema)(input);
`

$3

`typescript
// io-ts
interface PositiveBrand { readonly Positive: unique symbol }
const Positive = t.brand(t.number, (n): n is t.Branded => n > 0, 'Positive');

// Effect Schema
const Positive = pipe(S.Number, S.positive(), S.brand("Positive"));
`

$3

`typescript
// io-ts
const Tree = t.recursion('Tree', () => t.type({ children: t.array(Tree) }));

// Effect Schema
const Tree = S.Struct({ children: S.Array(S.suspend(() => Tree)) });
``

Related Packages

- schemashift-cli — CLI tool for running migrations
- @schemashift/core — Core analysis engine
- @schemashift/io-ts-zod — Alternative: io-ts → Zod

License

MIT