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graphql-tag

graphql-tag

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GraphQL printing and parsing with bundled dependencies. Includes:

  • gql A JavaScript template literal tag that parses GraphQL query strings into the standard GraphQL AST.
  • /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.

Babel preprocessing

GraphQL queries can be compiled at build time using babel-plugin-graphql-tag. Pre-compiling queries decreases the script initialization time and reduces the bundle size by potentially removing the need for graphql-tag at runtime.

React Native, Next.js

Additionally, in certain situations, preprocessing queries via the webpack loader is not possible. babel-plugin-inline-import-graphql-ast will allow one to import graphql files directly into your JavaScript by preprocessing GraphQL queries into ASTs at compile-time.

E.g.:

import myImportedQuery from './productsQuery.graphql'
 
class ProductsPage extends React.Component {
  ...
}

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.

Warnings

This package will emit a warning if you have multiple fragments of the same name. You can disable this with:

import { disableFragmentWarnings } from 'graphql-tag';
 
disableFragmentWarnings()