Support plan

• which support plan is this issue covered by?: Community
• is this issue currently blocking your project? (yes/no): yes
• is this issue affecting a production system? (yes/no): yes

Context

• node version: v10.16.3
• module version: 16.1.8
• environment (e.g. node, browser, native): node
• used with (e.g. hapi application, another framework, standalone, ...): none
• any other relevant information: none

What problem are you trying to solve?

I am currently working on upgrading Joi v15 to v16 and noticed using _ in rule names is not allowed in v16 because of the following regex.

For instance, with the following extension,

const Joi = require('@hapi/joi')

Joi.extend((joi) => {
  return {
    type: 'string',
    base: joi.string(),
    rules: {
      new_rule: {
        method() {
          return this.$_addRule('new_rule');
        },
        validate(value, helpers, args, options) {
          // validation goes here...
        },
      },
    },
  };
});

You will see this error:

[1] "rules.new_rule" is not allowed
    at Object.exports.process (/node_modules/@hapi/joi/lib/errors.js:183:16)
    at Object.internals.entry (/node_modules/@hapi/joi/lib/validator.js:140:26)
    at Object.exports.entry (/node_modules/@hapi/joi/lib/validator.js:26:30)
    at internals.Base.validate (/node_modules/@hapi/joi/lib/base.js:532:26)
    at Object.internals.assert (/node_modules/@hapi/joi/lib/index.js:221:27)
    at Object.assert (/node_modules/@hapi/joi/lib/index.js:102:19)
    at Object.extend (/node_modules/@hapi/joi/lib/index.js:166:18)
    at Object.<anonymous> (/test.js:3:5)
    at Module._compile (internal/modules/cjs/loader.js:778:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)

Is it possible to allow _ in rule names?

Do you have a new or modified API suggestion to solve the problem?

I would suggest just changing the regex to /^\w+$/(which is equivalent to /^[_a-zA-Z0-9]+$/) but I am not so sure how this would affect the entire functionality.