https://github.com/zth/graphql-generate-flow-schema-assets

Generate Flow assets from GraphQL schema.
https://github.com/zth/graphql-generate-flow-schema-assets

flow flowtype graphql graphql-schema javascript

Last synced: about 1 month ago
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Generate Flow assets from GraphQL schema.

• Host: GitHub
• URL: https://github.com/zth/graphql-generate-flow-schema-assets
• Owner: zth
• License: mit
• Created: 2017-12-10T19:55:08.000Z (almost 7 years ago)
• Default Branch: master
• Last Pushed: 2021-03-25T04:17:23.000Z (over 3 years ago)
• Last Synced: 2024-09-28T21:41:16.989Z (about 2 months ago)
• Topics: flow, flowtype, graphql, graphql-schema, javascript
• Language: JavaScript
• Size: 42 KB
• Stars: 13
• Watchers: 2
• Forks: 1
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE

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README

        
# graphql-generate-flow-schema-assets

A small lib to help generating various Flow assets from a GraphQL schema.

It currently finds all `enum` and `object` types in your schema and outputs them both as JS constants and as Flow types.

The point of this lib is to:

1. Make you rely on auto generated code straight from the source of truth (the schema),

instead of hard coding constants into your code.

1. Help type check and by that make your code resilient to change by providing a fully typed 

extraction of assets from your GraphQL schema. 

Ideally, this lib is used in combination with saving your schema from your backend.

Example in `package.json`:

```

"scripts": {

  ...

  "graphql:save-schema": "some-script-to-save-your-schema && npm run graphql:generate-assets",

  "graphql:generate-assets": "graphql-generate-flow-schema-assets -s path/to/schema.json --enums --object-types --enum-file-path ./src/constants/enums.js --object-types-file-path ./src/constants/object-types.js"

  ...

```

This way, your code always relies auto generated code 100% in sync with your backend.

If something changes in a incompatible way in the schema, Flow will tell you since the generated types will change.

## Installation

```

npm install -g graphql-generate-flow-schema-assets

```

## Usage

All options can be seen by running:

```

graphql-generate-flow-schema-assets -h

```

### Generating Enum constants

```

graphql-generate-flow-schema-assets -s path/to/schema.json --enums

```

This will generate a file containing all enums from your GraphQL schema

both as types and as actual objects. This means that instead of doing:

```

if (user.status === 'Active') {

...

```

You can do:

```javascript

import { UserStatuses } from '../path/to/enums.js';

if (user.status === UserStatuses.Active) {

...

```

...meaning it'll be type checked, auto completed by your editor/IDE, and all 

of that good stuff.

### Generating Object types

```

graphql-generate-flow-schema-assets -s path/to/schema.json --object-types

```

This will generate a file containing all object types from your GraphQL schema

both as types and as properties on one root object. This means that instead of doing:

```javascript

if (userOrSomeOtherType.__typename === 'User') {

  ...

```

You can do:

```javascript

import { ObjectTypes } from '../path/to/object-types.js';

if (userOrSomeOtherType.__typename === ObjectTypes.User) {

  ...

```

...meaning it'll be type checked, auto completed by your editor/IDE, and all 

of that good stuff.

### Extra

The lib `flow-enum-validator` is well suited to work with the enum output of this library to help validate unknown strings to enums. An example:

```javascript

// @flow

import { UserStatuses } from '../path/to/enums.js';

import { createEnumValidator } from 'flow-enum-validator';

// This will return a function that takes a string and returns if it's a valid part of the UserStatuses enum object, or void if it's not

const validateUserStatus = createEnumValidator(UserStatuses);

const userStatus = validateUserStatus(someRandomStringHere);

/**

 * Say UserStatuses is an object that looks like this: { Active: 'Active', Inactive: 'Inactive' }

 * Flow will now have refined userStatus to 'Active' | 'Inactive' | null | void.

 */

if (userStatus) {

  // userStatus is now 'Active' | 'Inactive'

}

```

Check out `flow-enum-validator` [here for more info and examples](https://github.com/zth/flow-enum-validator).