https://github.com/bcherny/flow-to-typescript

Convert Flow-annotated files to TypeScript
https://github.com/bcherny/flow-to-typescript

compiler flow flowtype javascript typescript

Last synced: 6 days ago
JSON representation

Convert Flow-annotated files to TypeScript

• Host: GitHub
• URL: https://github.com/bcherny/flow-to-typescript
• Owner: bcherny
• License: mit
• Created: 2017-11-29T07:56:14.000Z (almost 7 years ago)
• Default Branch: master
• Last Pushed: 2022-12-06T19:59:19.000Z (almost 2 years ago)
• Last Synced: 2024-10-18T11:26:28.120Z (18 days ago)
• Topics: compiler, flow, flowtype, javascript, typescript
• Language: TypeScript
• Size: 497 KB
• Stars: 430
• Watchers: 15
• Forks: 43
• Open Issues: 19
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.md

Awesome Lists containing this project

README

        
# Flow-to-TypeScript [![Build Status][build]](https://circleci.com/gh/bcherny/flow-to-typescript) [![npm]](https://www.npmjs.com/package/flow-to-typescript) [![mit]](https://opensource.org/licenses/MIT)

[build]: https://img.shields.io/circleci/project/bcherny/flow-to-typescript.svg?branch=master&style=flat-square

[npm]: https://img.shields.io/npm/v/flow-to-typescript.svg?style=flat-square

[mit]: https://img.shields.io/npm/l/flow-to-typescript.svg?style=flat-square

> Compile Flow files to TypeScript

**In Pre-Alpha - contributions welcome.**

## Installation

```sh

# Using Yarn:

yarn add flow-to-typescript

# Or, using NPM:

npm install flow-to-typescript --save

```

## Usage

### CLI

```sh

# Install globally

yarn global add flow-to-typescript

# Compile a file (all of these are equivalent)

flow2ts my/file.js.flow

flow2ts my/file.js.flow my/file.ts

flow2ts my/file.js.flow > my/file.ts

flow2ts -i my/file.js.flow -o my/file.ts

flow2ts --input my/file.js.flow --output my/file.ts

```

### Programmatic

```js

import { compile } from 'flow-to-typescript'

import { readFileSync, writeFileSync } from 'fs'

let path = 'path/to/file.js.flow'

let file = readFileSync(path, 'utf-8')

compile(file, path).then(ts =>

  writeFileSync('path/to/file.ts', ts)

)

```

## TypeScript vs. Flow

### Features

| Done? |             | Flow                                    | TypeScript |

|-------|-------------|-----------------------------------------|------------|

|   ✅  | Maybe       | `?type` (NullableTypeAnnotation)        | `type \| null \| undefined` |

|   ✅  | Null        | `null`                                  | `null` |

|   ✅  | Undefined   | `typeof undefined`                      | `undefined` |

|   ✅  | Mixed       | `mixed`                                 | `unknown` |

|   ✅  | Void        | `void`                                  | `void` |

|   ✅  | Functions   | `(A, B) => C`                           | `(a: A, b: B) => C` |

|   ⚔  | Predicates (0) | `(a: A, b: B) => %checks`            | `(a: A, b: B) => C` |

|   ⚔  | Predicates (1) | `(a: A, b: B) => C %checks`          | `(a: A, b: B) => C` |

|   ✅  | Exact types | `{\| a: A \|}`                            | `{ a: A }` |

|   ✅  | Indexers    | `{ [A]: B }`                            | `{ [a: A]: B }` |

|   ✅  | Opaque types | `opaque type A = B`                    | `type A = B` (not expressible) |

|   ✅  | Variance    | `interface A { +b: B, -c: C }`          | `interface A { readonly b: B, c: C }` |

|   ✅  | Bounds      | ``                           | `` |

|   ✅  | Casting     | `(a: A)`                                | `(a as A)` |

|   ✅  | Import default type | `import type A from './b'`          | `import A from './b'` |

|   ✅  | Import named type | `import type { A } from './b'`          | `import { A } from './b'` |


### Utilities

| Done? |             | Flow                                    | TypeScript |

|-------|-------------|-----------------------------------------|------------|

|       | Keys        | `$Keys`                              | `keyof A` |

|       | Values      | `$Values`                            | `A[keyof A]` |

|   ✅  | ReadOnly    | `$ReadOnly`                          | `Readonly` |

|   ✅  | Exact       | `$Exact`                             | `A` |

|       | Difference  | `$Diff`                           | TODO` |

|       | Rest        | `$Rest`                           | `Exclude` |

|       | Property type | `$PropertyType`                 | `T[k]` |

|       | Element type | `$ElementType`                   | `T[k]` |

|       | Dependent type | `$ObjMap`                      | TODO |

|       | Mapped tuple | `$TupleMap`                      | TODO |

|       | Return type | `$Call`                              | `ReturnType` |

|       | Class       | `Class`                              | `typeof A` |

|       | Supertype   | `$Supertype`                         | `any` (warn - vote for https://github.com/Microsoft/TypeScript/issues/14520) |

|       | Subtype     | `$Subtype`                           | `B extends A` |

|       | Existential type | `*`                                | `any` (warn - vote for https://github.com/Microsoft/TypeScript/issues/14466) |


✅ Done

⚔ Babylon doesn't support it (yet)