Populate context.options with the default values when no options are present

The version of ESLint you are using.

7.14.0

The problem you want to solve.

When writing a plugin, I want to specify some default value for the rules. However, when the end-user don’t specify any option, nothing is passed to the rule context.

This kind of kill the point of default values in the schema.

Your take on the correct solution to problem.

Apparently, AJV fill the schema with the default value in place. It means that is no object is passed down, it can’t fill it.

I think, passing an empty object if no options are specified could solve the issue.

Are you willing to submit a pull request to implement this change?

Yes

I already made a minimal reproduction repo.

[mdjermanovic]

why there’s a difference between “no options” and “empty option”

That’s how Ajv works, probably for a good reason. Is there a JSON Schema validator that works differently? I think that modifying the schema validation process to a (most likely) uncommon behavior is too complex and out of scope for ESLint.

What does seem to work with Ajv is setting defaults for objects, which then also get validated against the object’s schema in the same way, including applying defaults:

const schema = {
  type: "array",
  items: [
      {
          type: "object",
          properties: {
              first: {
                  type: "string",
                  default: "Here I am !"
              },
              second: {
                  type: "string",
                  default: "Me too"
              }
          },
          additionalProperties: false,
          default: {} // <--
      }
  ],
  minItems: 0,
  maxItems: 1
};

const Ajv = require("ajv");

const ajv = new Ajv({ useDefaults: true });

const validate = ajv.compile(schema);

const data = [ /* nothing */ ];

validate(data);

console.log(data); // [ { first: 'Here I am !', second: 'Me too' } ]

So it looks like you could add default: {} in the rule’s schema to enforce creating an object with default values when user doesn’t specify anything.

An issue with this approach is that ESLint currently doesn’t support default in top-level arrays, as noticed in https://github.com/eslint/eslint/issues/11749. We’re passing a temporary array (Array.isArray(options) ? options.slice(1) : []) to Ajv, so any changes that validation makes directly on the provided array are lost, unlike changes on deep objects. I think we can consider making this enhancement/bug fix.

[eslint-deprecated[bot]]

Unfortunately, it looks like there wasn’t enough interest from the team or community to implement this change. While we wish we’d be able to accommodate everyone’s requests, we do need to prioritize. We’ve found that issues failing to reach accepted status after 21 days tend to never be accepted, and as such, we close those issues. This doesn’t mean the idea isn’t interesting or useful, just that it’s not something the team can commit to.

Thanks for contributing to ESLint and we appreciate your understanding.