Tiva

⏱️ EXPENSIVE plain object type validator leverages TypeScript language service.

Why

Category	Complex Type	Extended Validation	Zero Build Setups	Performance
Tiva	Yes	Yes	Yes	In many case not tolerable
ajv alike	Yes	Yes*	No	Much much better than Tiva
io-ts alike	Limited**	Yes	Yes	Much much better than Tiva

* Extra efforts might be needed for extended validation to work with TypeScript declarations.

** We have many types that are evaluated from pure type declarations, and those type declarations are used in other part of our project for type checking and intellisense purpose. And aside from that, writing complex type with those tools will not be as pleasant as natural type declarations.

Usage

yarn add tiva

import {Tiva} from 'tiva';
 
let tiva = new Tiva();
 
tiva.validate('string[]', ['foo', 'bar']).then(console.info, console.error);
 
tiva
  .validate(
    {module: 'module-specifier', type: 'AwesomeType'},
    {foo: 'abc', bar: 123},
  )
  .then(console.info, console.error);

Extensions

Tiva can validate with extended validator functions that matches by @tag in JSDoc comments (one tag per line):

interface Foo {
  /** @uuid */
  id: string;
}

There are a few built-in extensions:

• @pattern <pattern> Validate by regular expression pattern.
• @uuid [version] UUID.
• @unique [group] Validate that there's no more than one occurrence.

Checkout @built-in-extensions.ts for implementation details.

Writing custom extensions is easy:

let tiva = new Tiva({
  extensions: {
    custom(value) {
      if (value === 'custom') {
        return undefined;
      }
 
      return `Value "${value}" must be "custom"`;
    },
  },
});

How it works

Tiva provides a Validator class that synchronously manipulates TypeScript language service to do the heavy lifting; and a Tiva class that creates a worker to run Validator in another thread.

The type check part is simple: it just gets the diagnostic messages from TypeScript by fabricating a variable statement. The tricky part is the extended validation.

Here's how Tiva does it:

1. It recursively visits the types used by the type to be validate against.
2. It find tags like @uuid in those types, and asks TypeScript to find the implementations within the plain object to be validated.
3. It then validates the value against the extension.

Again the heavy lifting is done by the TypeScript language service. And doing this way also makes it possible to have Tiva work with complex types including condition types, mapping types etc.

License

MIT License.