chore(v2): use joi for config validation

[anshulrgoyal]

Motivation

More robust validation for config. Validating more fields and types. It fixes #2978.

Have you read the Contributing Guidelines on pull requests?

yes

Test Plan

I have added tests for validation and update old ones

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[slorber]

That looks good

Would just factorize a bit the tests, and test for empty config

[slorber]

What about extracting this in a "baseConfig" variable?

Maybe it could be more convenient to have such method to make tests less "verbose"

const testConfig = (config) => Joi.attempt({...baseConfig,...config})

[anshulrgoyal]

Good idea , I will fix it.

[slorber]

see comments

[slorber]

This is not really what I meant :p

The idea is that you don't need to mention the 4 required attributes in every test to avoid unnecessary boilerplate.

There are many ways to do here, here's an idea:

const baseTestConfig = {
  baseUrl: "/",
  favicon: "some.ico",
  title: "my site",
  url: "https://mysite.com"
};

const testConfig = config =>
  Joi.attempt({...baseTestConfig,...config}, ConfigSchema);

const expectConfig = config =>     expect(config).toEqual({
      ...DEFAULT_CONFIG,
      ...baseTestConfig,
      ...config,
    });

  test('custom fields', () => {
    const value = testConfig({
      customFields: {
        author: 'anshul',
      },
    });
    expectConfig({
      customFields: {
        author: 'anshul',
      },
    });
}

[slorber]

here it would be better to abortEarly: false

so you need to catch the potential validationError, extract all the errors, and rethrow as a well-formatted regular error (with line breaks etc...)

[anshulrgoyal]

pr failed due to weird "no internet connection".

[slorber]

LGTM