@thelabnyc/ts-to-io

Converts TypeScript type and interface definitions into io-ts type validators.

Usage

As a script

npm install -g @thelabnyc/ts-to-io
ts-to-io file.ts

or

npx @thelabnyc/ts-to-io file.ts

From code

NOTE: The validator generation is not intended to be performed at runtime. You should first generate the validators locally and then include them in the program source.

import { getValidatorsFromString } from "@thelabnyc/ts-to-io";

const sourceString = `
  type Person = { name: string; age: number | null }
`;

const validators = getValidatorsFromString(sourceString);

Configuration

ts-to-io supports the following config options

| Key | CLI opt | Default | Description | | --------------- | --------------------- | ------- | ---------------------------------------------------- | | followImports | --follow-imports | false | output codecs for types declared in imported files | | includeHeader | --no-include-header | true | omit io-ts import from the output | | newtypeMode | --newtype-mode | none | newtype generation mode: none or all (see below) |

Newtype Mode

When newtypeMode is set to all, primitive type aliases are converted to newtype-ts nominal types, providing type safety for distinguishing between different uses of the same primitive type.

Example

// Input
export type Latitude = string;
export type Longitude = string;
export interface Location {
    lat: Latitude;
    lng: Longitude;
}

With newtypeMode: 'none' (default):

import * as t from "io-ts";

const Latitude = t.string;
const Longitude = t.string;
const Location = t.type({ lat: t.string, lng: t.string });

With newtypeMode: 'all':

import * as t from "io-ts";
import { fromNewtype } from "io-ts-types/lib/fromNewtype";
import { Newtype, iso } from "newtype-ts";

export interface ILatitude
    extends Newtype<{ readonly ILatitude: unique symbol }, string> {}
export const Latitude = fromNewtype<ILatitude>(t.string);
export const isoLatitude = iso<ILatitude>();

export interface ILongitude
    extends Newtype<{ readonly ILongitude: unique symbol }, string> {}
export const Longitude = fromNewtype<ILongitude>(t.string);
export const isoLongitude = iso<ILongitude>();

const Location = t.type({ lat: Latitude, lng: Longitude });

CLI Usage

ts-to-io --newtype-mode all input.ts

Programmatic Usage

import { defaultConfig, getValidatorsFromString } from "@thelabnyc/ts-to-io";

const validators = getValidatorsFromString(sourceString, {
    ...defaultConfig,
    newtypeMode: "all",
});

Peer Dependencies

When using newtypeMode: 'all', the following peer dependencies are required:

• io-ts-types (^0.5.19)
• newtype-ts (^0.3.4)
• fp-ts (^2.16.0)

Supported types

| Type | Supported | TypeScript | codec | | --------------- | --------- | ---------------------------------- | ------------------------------- | | string | ✅ | string | t.string | | number | ✅ | number | t.number | | boolean | ✅ | boolean | t.boolean | | null | ✅ | null | t.null | | undefined | ✅ | undefined | t.undefined | | void | ✅ | void | t.void | | any, unknown | ✅ | any, unknown | t.unknown | | array | ✅ | Array<A> | t.array(A) | | record | ✅ | Record<K, A> | t.record(K, A) | | object type | ✅ | { name: string } | t.type({ name: t.string }) | | interface | ✅ | interface I { name: string } | t.type({ name: t.string }) | | literal | ✅ | 'ABC' | t.literal('ABC') | | partial | ✅ | Partial<{ name: string }> | t.partial({ name: t.string }) | | readonly | ❌ | Readonly<A> | - | | readonly array | ❌ | ReadonlyArray<A> | - | | tuple | ✅ | [ A, B ] | t.tuple([ A, B ]) | | tuple with rest | ❌ | [ A, B, ...C ] | - | | union | ✅ | A \| B | t.union([ A, B ]) | | intersection | ✅ | A & B | t.intersection([ A, B ]) | | keyof | ❌ | keyof M | - | | recursive type | ❌ | type Node = { children: Node[] } | - | | function | ✅ | type fn = () => string | t.Function |