how to manipulate Joi messages by http request?

Question

I have a user schema like the code below:

const Joi = require("joi");
const message = require("./types/string");

const username = Joi.string()
  .regex(/^[A-Za-z0-9]+$/)
  .required()
  .min(5)
  .max(20)
  .messages(message);

const email = Joi.string()
  .regex(/^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/)
  .required()
  .min(5)
  .max(255)
  .email()
  .messages(message);

const password = Joi.string()
  .regex(/^[A-Za-z0-9]+$/)
  .required()
  .min(5)
  .max(255)
  .messages(message);

const userSchema = Joi.object({
  username,
  password,
  email,
});

exports.userSchema = { route: "/users", object: userSchema };

and a schema validation like the code below that I have found at https://www.digitalocean.com/community/tutorials/how-to-use-joi-for-node-api-schema-validation:

const _ = require("lodash");
const { StatusCodes } = require("http-status-codes");
const { Schemas } = require("../joi-schema-validation");

exports.schemaValidator = function (useJoiError = false) {
  const _useJoiError = _.isBoolean(useJoiError) && useJoiError;
  const _supportedMethods = ["post", "put", "patch"];

  const _validationOptions = {
    abortEarly: false,
    allowUnknown: true,
    stripUnknown: true,
  };

  return (req, res, next) => {
    const route = req.route.path;
    const method = req.method.toLowerCase();

    const schema = Schemas.find(
      (schema) => schema.route === route.replace("/:id", "")
    );

    if (_.includes(_supportedMethods, method) && schema) {
      const { object } = schema;
      const { error, value } = object.validate(req.body, _validationOptions);

      if (error) {
        const JoiError = {
          status: "failed",
          validationErrors: {
            details: _.map(error.details, ({ message, context }) => ({
              [context.label]: req.t(message.replace(/['"]/g, "")),
            })),
          },
        };

        const CustomError = {
          status: "failed",
          error: "Invalid request data. Please review request and try again.",
        };

        return res
          .status(StatusCodes.BAD_REQUEST)
          .json(_useJoiError ? JoiError : CustomError);
      } else {
        req.body = value;
        return next();
      }
    }
    return next();
  };
};

Let's say I have two locales joi messages, one in english and one in spanish. How can I switch to locale joi messages if "Accept-Language" header is "es-es" lcid?

Answer 1

After digging around and slept over it, I've manage to come up with an easy solution. In the beginning of the route handler middleware, i have a "messages" variable where I check the request header accept language. If the language LCID is "en" then I return the english error messages or return default error messages, in my case the dutch language error messages. Before validating, I pass the return error messages into the messages method of my schema and then chain the validate function to it.

The updated code looks now like code underneath:

const _ = require("lodash");
const { StatusCodes } = require("http-status-codes");
const { Schemas } = require("../joi-schema-validation");

exports.schemaValidator = function (useJoiError = false) {
  const _useJoiError = _.isBoolean(useJoiError) && useJoiError;
  const _supportedMethods = ["post", "put", "patch"];

  const _validationOptions = {
    abortEarly: false,
    allowUnknown: true,
    stripUnknown: true,
  };

  return (req, res, next) => {
    const messages =
      req.headers["accept-language"] === "en"
        ? require("../joi-schema-validation/types/string")
        : require("../joi-schema-validation/types/string-nl");
        
    const route = req.route.path;
    const method = req.method.toLowerCase();

    const schema = Schemas.find(
      (schema) => schema.route === route.replace("/:id", "")
    );

    if (_.includes(_supportedMethods, method) && schema) {
      const { object } = schema;
      const { error, value } = object
        .messages(messages)
        .validate(req.body, _validationOptions);

      if (error) {
        const JoiError = {
          status: "failed",
          validationErrors: {
            details: _.map(error.details, ({ message, context }) => ({
              [context.label]: message.replace(/['"]/g, ""),
            })),
          },
        };

        const CustomError = {
          status: "failed",
          error: "Invalid request data. Please review request and try again.",
        };

        return res
          .status(StatusCodes.BAD_REQUEST)
          .json(_useJoiError ? JoiError : CustomError);
      } else {
        req.body = value;
        return next();
      }
    }
    return next();
  };
};

If there are any comments or alternatives for this solution, I'm more than happy to read about them.

Happy coding