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GraphQL Tools

GraphQL Tools

A set of utilities for faster GraphQL development

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Resolvers composition#

Composition tool for GraphQL, with helpers to combine multiple resolvers into one, specify dependencies between fields, and more.

When developing a GraphQL server, it is common to perform some authorization logic on your resolvers, usually based on the context of a request. With Resolvers Composition you can easily accomplish that and still make the code decoupled - thus testable - by combining multiple single-logic resolvers into one.

The following is an example of a simple logged-in authorization logic:

Instead of doing this,

const resolvers = { Query: { myQuery: (root, args, context) => { // Make sure that the user is authenticated if (!context.currentUser) { throw new Error('You are not authenticated!') } // Make sure that the user has the correct roles if (!context.currentUser.roles || context.currentUser.roles.includes('EDITOR')) { throw new Error('You are not authorized!') } // Business logic if (args.something === '1') { return true } return false } } }

You can do;

const { composeResolvers } = require('@graphql-tools/resolvers-composition') const resolvers = { Query: { myQuery: (root, args, context) => { if (args.something === '1') { return true } return false } } } const isAuthenticated = () => next => async (root, args, context, info) => { if (!context.currentUser) { throw new Error('You are not authenticated!') } return next(root, args, context, info) } const hasRole = (role: string) => next => async (root, args, context, info) => { if (!context.currentUser.roles || context.currentUser.roles.includes(role)) { throw new Error('You are not authorized!') } return next(root, args, context, info) } const resolversComposition = { 'Query.myQuery': [isAuthenticated(), hasRole('EDITOR')] } const composedResolvers = composeResolvers(resolvers, resolversComposition)

composeResolvers is a method in @graphql-tools/resolvers-composition package that accepts IResolvers object and mappings for composition functions that would be run before resolver itself.

Supported path matcher format#

The paths for resolvers support * wildcard for types and glob patters for fields, eg:

  • *.* - all types and all fields
  • Query.* - all queries
  • Query.single - only a single query
  • Query.{first, second} - queries for first/second
  • Query.!first - all queries but first
  • Query.!{first, second} - all queries but first/second