Validate GraphQL fields
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Latest commit 13e0985 Sep 22, 2018

README.md

graphql-constraint-directive

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Allows using @constraint as a directive to validate input data. Inspired by Constraints Directives RFC and OpenAPI

Install

npm install graphql-constraint-directive

Usage

const ConstraintDirective = require('graphql-constraint-directive')
const express = require('express')
const bodyParser = require('body-parser')
const { graphqlExpress } = require('apollo-server-express')
const { makeExecutableSchema } = require('graphql-tools')
const typeDefs = `
  type Query {
    books: [Book]
  }
  type Book {
    title: String
  }
  type Mutation {
    createBook(input: BookInput): Book
  }
  input BookInput {
    title: String! @constraint(minLength: 5, format: "email")
  }`
const schema = makeExecutableSchema({
  typeDefs, schemaDirectives: { constraint: ConstraintDirective }
})
const app = express()

app.use('/graphql', bodyParser.json(), graphqlExpress({ schema }))

API

String

minLength

@constraint(minLength: 5) Restrict to a minimum length

maxLength

@constraint(maxLength: 5) Restrict to a maximum length

startsWith

@constraint(startsWith: "foo") Ensure value starts with foo

endsWith

@constraint(endsWith: "foo") Ensure value ends with foo

contains

@constraint(contains: "foo") Ensure value contains foo

notContains

@constraint(notContains: "foo") Ensure value does not contain foo

pattern

@constraint(pattern: "^[0-9a-zA-Z]*$") Ensure value matches regex, e.g. alphanumeric

format

@constraint(format: "email") Ensure value is in a particular format

Supported formats:

  • byte: Base64
  • date-time: RFC 3339
  • date: ISO 8601
  • email
  • ipv4
  • ipv6
  • uri
  • uuid

Int/Float

min

@constraint(min: 3) Ensure value is greater than or equal to

max

@constraint(max: 3) Ensure value is less than or equal to

exclusiveMin

@constraint(exclusiveMin: 3) Ensure value is greater than

exclusiveMax

@constraint(exclusiveMax: 3) Ensure value is less than

multipleOf

@constraint(multipleOf: 10) Ensure value is a multiple

ConstraintDirectiveError

Each validation error throws a ConstraintDirectiveError. Combined with a formatError function, this can be used to customise error messages.

{
  code: 'ERR_GRAPHQL_CONSTRAINT_VALIDATION',
  fieldName: 'theFieldName',
  context: [ { arg: 'argument name which failed', value: 'value of argument' } ]
}
const formatError = function (error) {
  if (error.originalError && error.originalError.code === 'ERR_GRAPHQL_CONSTRAINT_VALIDATION') {
    // return a custom object
  }

  return error
}

app.use('/graphql', bodyParser.json(), graphqlExpress({ schema, formatError }))