A simple package for throwing graphql validation error with localization.

Installing

npm install --save gql-error

How to use

This library provides two function validate() and error()
validate() can be used for form validations and error() can be used to throw normal graphql error.

validate(input, rules[, options]) takes 3 parameter
First parameter: input object we get from graphql. Ex: {email: "[email protected]", password: "gqlvalidator"}
Second parameter: rules for validation (example below).
Third parameter: options for localization and others.

error(message[, options]) takes 2 parameter
First parameter: concatenated string that matches json path in config files as shown below.
Second parameter: same as above third parameter.

localizeString(message[, options]) takes 2 parameter (This API actually doesn't throw any error but returns a localized message from our locale config files.) First parameter: concatenated string that matches json path in config files as shown below.

Options

• lang (string) - Which localization to use. Default 'en'.
• gql (boolean) - If true uses throws graphql error. If false, throws error as original nodejs error. Default true.

Example

Authentication example:
auth.resolver.js

import GQLError from 'gql-validator';
import rules from './auth.validation';

const resolvers = {
  Mutation: {
    login: (_, { input }, req) => {
      let lang = req.header('Accept-Language'); //en
      GQLError.validate(input, rules.login(), { lang: lang });

      return User
        .findOne({email: input.email})
        .then(user => {
          if (!user) GQLError.error('user.email.notFound', {lang: lang});

          if (input.password == 'gqlvalidator') {
            GQLError.error('user.password.incorrect', {lang: lang});
          }

          return user;
        })
        .catch(err => {
          throw err;
        })
    },

    register: (_, { input }, req) => {
      let lang = req.header('Accept-Language'); //se
      GQLError.validate(input, rules.register(), { lang: lang });

      return User
        .findOne({ where: { email: input.email } })
        .then(res => {
            if (res) GQLError.error('user.email.notAvailable', { lang: lang });

            return User
              .create({
                email: input.email,
                password: input.password
              })
              .then(user => {
                return user;
              })
              .catch(err => {
                throw err;
              });
        })
        .catch(err => {
          throw err;
        });
    }

validation rules (I used a different file ./auth.validation.js)
To learn more about rule convention, see how to make constraints here: http://validatejs.org

const rules = {
  register: () => {
    return {
      email: {
        presence: { message: "user.email.required" },
        email: { message: "user.email.invalid" }
      },
      password: {
        presence: { message: "user.password.required" },
        length: {
          minimum: 3, message: "user.password.minimum"
        }
      }
    };
  },
  
  login: () => {
    // rules here
  }
}

Message config files: en.json

{
  "user": {
    "email": {
      "required": "Email is required",
      "invalid": "Invalid email address",
      "notAvailable": "Email address not available",
      "notFound": "Email address not found"
    },
    "password": {
      "required": "Password is required",
      "minimum": "Minimum 3 character required",
      "incorrect": "Password is incorrect"
    }
  }
}

se.json (Used google translator, you get the idea :D)

{
  "user": {
    "email": {
      "required": "E-post krävs",
      "invalid": "Ogiltig e-postadress",
      "notAvailable": "E-postadressen är inte tillgänglig",
      "notFound": "E-postadressen hittades inte"
    },
    "password": {
      "required": "Lösenord krävs",
      "minimum": "Minst 3 tecken krävs",
      "incorrect": "Lösenord är inkorrekt"
    }
  }
}

You need to create separate files for different locales. Name should match exactly what you will use in option {lang: en}.

Example:
app\
--config\
----locales
------en.json
------se.json
------fr.json

For now your json file structure and path should look exactly like above.

Note:

In order to provide lang option either you will need to have access to 'Accept-Language' header option found in request inside graphql resolver or you need to find a way to provide lang option for third parameter for localisation. In above example I have passed req object as a third parameter in resolver.