A JavaScript template literal tag that parses GraphQL queries
JavaScript
Latest commit 41b6076 Feb 22, 2017 @jnwng jnwng committed on GitHub Update CHANGELOG.md

README.md

graphql-tag

npm version Build Status Get on Slack

GraphQL printing and parsing with bundled dependencies. Includes:

  • gql A JavaScript template literal tag that parses GraphQL query strings into the standard GraphQL AST.
  • /parser A bundled version of graphql/language/parser, that builds correctly in React Native.
  • /printer A bundled version of graphql/language/printer, that builds correctly in React Native.
  • /loader A webpack loader to preprocess queries

gql

This is a template literal tag you can use to concisely write a GraphQL query that is parsed into the standard GraphQL AST:

import gql from 'graphql-tag';

const query = gql`
  {
    user(id: 5) {
      firstName
      lastName
    }
  }
`

// query is now a GraphQL syntax tree object
console.log(query);

// {
//   "kind": "Document",
//   "definitions": [
//     {
//       "kind": "OperationDefinition",
//       "operation": "query",
//       "name": null,
//       "variableDefinitions": null,
//       "directives": [],
//       "selectionSet": {
//         "kind": "SelectionSet",
//         "selections": [
//           {
//             "kind": "Field",
//             "alias": null,
//             "name": {
//               "kind": "Name",
//               "value": "user",
//               ...

You can easily explore GraphQL ASTs on astexplorer.net.

This package is the way to pass queries into Apollo Client. If you're building a GraphQL client, you can use it too!

Why use this?

GraphQL strings are the right way to write queries in your code, because they can be statically analyzed using tools like eslint-plugin-graphql. However, strings are inconvenient to manipulate, if you are trying to do things like add extra fields, merge multiple queries together, or other interesting stuff.

That's where this package comes in - it lets you write your queries with ES2015 template literals and compile them into an AST with the gql tag.

Caching parse results

This package only has one feature - it caches previous parse results in a simple dictionary. This means that if you call the tag on the same query multiple times, it doesn't waste time parsing it again. It also means you can use === to compare queries to check if they are identical.

Webpack preprocessing

This package also includes a webpack loader. There are many benefits over this approach, which saves GraphQL ASTs processing time on client-side and enable queries to be separated from script over .graphql files.

loaders: [
  {
    test: /\.(graphql|gql)$/,
    exclude: /node_modules/,
    loader: 'graphql-tag/loader'
  }
]

then:

import query from './query.graphql';

console.log(query);
// {
//   "kind": "Document",
// ...

Testing environments that don't support Webpack require additional configuration. For Jest use jest-transform-graphql.

Parser and printer

This package also includes two submodules: graphql-tag/printer and graphql-tag/parser, which are bundled versions of the corresponding modules from the standard graphql package. These are included because the graphql package currently doesn't build in React Native. Use them the same way you would use the relevant modules from graphql:

import { parse } from 'graphql-tag/parser';
import { print } from 'graphql-tag/printer';

Why are these included in the source on GitHub?

We generate the bundles for the printer and parser with Webpack from the graphql package. You might notice the bundles are included in the package source on GitHub. This is to enable easy installation from a Git URL in cases where that is helpful. In the case of updates to graphql printing or parsing (which should be very rare since the syntax is stable at this point), we will be able to easily run the build script and republish.