gcanti/babel-plugin-tcomb

npm install --save-dev tcomb
npm install --save-dev babel-plugin-tcomb

{
  "plugins" : [
    "syntax-flow",
    "tcomb",
    "transform-flow-strip-types"
  ]
}

"plugins" : [
  ["tcomb", {
    globals: [
      // flow
      {
        'Class': true
      }
      // react
      {
        'SyntheticEvent': true,
        ...
      },
      // your custom global types (if any)
      ...
    ]
  }],
]

// index.js

function sum(a: number, b: number) {
  return a + b
}

sum(1, 'a') // <= typo

index.js:7
  7: sum(1, 'a')
     ^^^^^^^^^^^ function call
  7: sum(1, 'a')
            ^^^ string. This type is incompatible with
  3: function sum(a: number, b: number) {
                                ^^^^^^ number

Uncaught TypeError: [tcomb] Invalid value "a" supplied to b: Number

// index.js

type Person = {
  name: string, // required string
  surname?: string, // optional string
  age: number,
  tags: Array<string>
};

function getFullName(person: Person) {
  return `${person.name} ${person.surname}`
}

getFullName({ surname: 'Canti' })

index.js:14
 14: getFullName({
     ^ function call
 10: function getFullName(person: Person) {
                                  ^^^^^^ property `name`. Property not found in
 14: getFullName({
                 ^ object literal

TypeError: [tcomb] Invalid value undefined supplied to person: Person/name: String

import type { $Refinement } from 'tcomb'

// define your predicate...
const isInteger = n => n % 1 === 0

// ...and pass it to the suitable intersection type
type Integer = number & $Refinement<typeof isInteger>;

function foo(n: Integer) {
  return n
}

foo(2)   // flow ok, tcomb ok
foo(2.1) // flow ok, tcomb throws [tcomb] Invalid value 2.1 supplied to n: Integer
foo('a') // flow throws, tcomb throws

import type { $Reify } from 'tcomb'

type Person = { name: string };

const ReifiedPerson = (({}: any): $Reify<Person>)
console.log(ReifiedPerson.meta) // => { kind: 'interface', props: ... }

type User = { name: string };

export function loadUser(userId: string): Promise<User> {
  return axios.get('...').then(p => (p: User)) // <= type cast
}

// recursive
type Path = {
  node: Node,
  parentPath: Path
};

import { createStore } from 'redux'

// types
type State = number;
type ReduxInitAction = { type: '@@redux/INIT' };
type Action = ReduxInitAction
  | { type: 'INCREMENT', delta: number }
  | { type: 'DECREMENT', delta: number };

function reducer(state: State = 0, action: Action): State {
  switch(action.type) {
    case 'INCREMENT' :
      return state + action.delta
    case 'DECREMENT' :
      return state - action.delta
  }
  return state
}

type Store = {
  dispatch: (action: Action) => any;
};

const store: Store = createStore(reducer)

store.dispatch({ type: 'INCREMEN', delta: 1 }) // <= typo

// throws [tcomb] Invalid value { "type": "INCREMEN", "delta": 1 } supplied to action: Action
// Flow throws as well

// @flow

import React from 'react'
import ReactDOM from 'react-dom'
import { props } from 'tcomb-react'

type Props = {
  name: string
};

@props(Props)
class Hello extends React.Component<void, Props, void> {
  render() {
    return <div>Hello {this.props.name}</div>
  }
}


ReactDOM.render(<Hello />, document.getElementById('app'))

index.js:12
 12: class Hello extends React.Component<void, Props, void> {
                                               ^^^^^ property `name`. Property not found in
 19: ReactDOM.render(<Hello />, document.getElementById('app'))
                     ^^^^^^^^^ props of React element `Hello`

Warning: Failed propType: [tcomb] Invalid prop "name" supplied to Hello, should be a String.

Detected errors (1):

  1. Invalid value undefined supplied to String

{
  "presets": ["react", "es2015"],
  "passPerPreset": true,
  "plugins" : [
    "tcomb",
    "transform-decorators-legacy"
  ]
}

// @flow

import React from 'react'
import ReactDOM from 'react-dom'
import { propTypes } from 'tcomb-react'
import type { $Reify } from 'tcomb'

type Props = {
  name: string
};

class Hello extends React.Component<void, Props, void> {
  render() {
    return <div>Hello {this.props.name}</div>
  }
}

Hello.propTypes = propTypes((({}: any): $Reify<Props>))

ReactDOM.render(<Hello />, document.getElementById('app'))

type MyString = string;
type MyNumber = number;
type MyBoolean = boolean;
type MyVoid = void;
type MyNull = null;

import _t from "tcomb";

const MyString = _t.String;
const MyNumber = _t.Number;
const MyBoolean = _t.Boolean;
const MyVoid = _t.Nil;
const MyNull = _t.Nil;

const x: number = 1

const x = _assert(x, _t.Number, "x");

function sum(a: number, b: number): number {
  return a + b
}

import _t from "tcomb";

function sum(a, b) {
  _assert(a, _t.Number, "a");
  _assert(b, _t.Number, "b");

  const ret = function (a, b) {
    return a + b;
  }.call(this, a, b);

  _assert(ret, _t.Number, "return value");
  return ret;
}

type Person = {
  name: string,
  surname: ?string,
  age: number,
  tags: Array<string>
};

import _t from "tcomb";

const Person = _t.interface({
  name: _t.String,
  surname: _t.maybe(_t.String),
  age: _t.Number,
  tags: _t.list(_t.String)
}, "Person");