om/node_modules/eslint-visitor-keys/lib/index.js

/**
 * @author Toru Nagashima <https://github.com/mysticatea>
 * See LICENSE file in root directory for full license.
 */
"use strict";

const KEYS = require("./visitor-keys.json");

// Types.
const NODE_TYPES = Object.freeze(Object.keys(KEYS));

// Freeze the keys.
for (const type of NODE_TYPES) {
    Object.freeze(KEYS[type]);
}
Object.freeze(KEYS);

// List to ignore keys.
const KEY_BLACKLIST = new Set([
    "parent",
    "leadingComments",
    "trailingComments"
]);

/**
 * Check whether a given key should be used or not.
 * @param {string} key The key to check.
 * @returns {boolean} `true` if the key should be used.
 */
function filterKey(key) {
    return !KEY_BLACKLIST.has(key) && key[0] !== "_";
}

//------------------------------------------------------------------------------
// Public interfaces
//------------------------------------------------------------------------------

module.exports = Object.freeze({

    /**
     * Visitor keys.
     * @type {{ [type: string]: string[] | undefined }}
     */
    KEYS,

    /**
     * Get visitor keys of a given node.
     * @param {Object} node The AST node to get keys.
     * @returns {string[]} Visitor keys of the node.
     */
    getKeys(node) {
        return Object.keys(node).filter(filterKey);
    },

    // Disable valid-jsdoc rule because it reports syntax error on the type of @returns.
    // eslint-disable-next-line valid-jsdoc
    /**
     * Make the union set with `KEYS` and given keys.
     * @param {Object} additionalKeys The additional keys.
     * @returns {{ [type: string]: string[] | undefined }} The union set.
     */
    unionWith(additionalKeys) {
        const retv = Object.assign({}, KEYS);

        for (const type of Object.keys(additionalKeys)) {
            if (retv.hasOwnProperty(type)) {
                const keys = new Set(additionalKeys[type]);

                for (const key of retv[type]) {
                    keys.add(key);
                }

                retv[type] = Object.freeze(Array.from(keys));
            } else {
                retv[type] = Object.freeze(Array.from(additionalKeys[type]));
            }
        }

        return Object.freeze(retv);
    }
});