graphql-constraint-directive

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

Install

npm install graphql-constraint-directive

Usage

1const { constraintDirective, constraintDirectiveTypeDefs } = require('graphql-constraint-directive')
2const express = require('express')
3const { ApolloServer } = require('apollo-server-express')
4const { makeExecutableSchema } = require('graphql-tools')
5const typeDefs = `
6  type Query {
7    books: [Book]
8  }
9  type Book {
10    title: String
11  }
12  type Mutation {
13    createBook(input: BookInput): Book
14  }
15  input BookInput {
16    title: String! @constraint(minLength: 5, format: "email")
17  }`
18const schema = makeExecutableSchema({
19  typeDefs: [constraintDirectiveTypeDefs, typeDefs],
20  schemaTransforms: [constraintDirective()]
21})
22const app = express()
23const server = new ApolloServer({ schema })
24
25server.applyMiddleware({ app })
26

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

oneOf

@constraint(oneOf: ['test', 'hello']) Value should be equal to one of the strings supplied

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

Lists

minListLength

@constraint(minListLengt: 10) Ensure list length is greater than

maxListLength

@constraint(maxListLengt: 10) Ensure list length is less than

ConstraintDirectiveError

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

1{
2  code: 'ERR_GRAPHQL_CONSTRAINT_VALIDATION',
3  fieldName: 'theFieldName',
4  context: [ { arg: 'argument name which failed', value: 'value of argument' } ]
5}

1const formatError = function (error) {
2  if (error.originalError && error.originalError.code === 'ERR_GRAPHQL_CONSTRAINT_VALIDATION') {
3    // return a custom object
4  }
5
6  return error
7}
8
9app.use('/graphql', bodyParser.json(), graphqlExpress({ schema, formatError }))
10

uniqueTypeName

@constraint(uniqueTypeName: "Unique_Type_Name") Override the unique type name generate by the library to the one passed as an argument