--- /dev/null
+/**
+ * @fileoverview Rule Validator
+ * @author Nicholas C. Zakas
+ */
+
+"use strict";
+
+//-----------------------------------------------------------------------------
+// Requirements
+//-----------------------------------------------------------------------------
+
+const ajv = require("../shared/ajv")();
+
+//-----------------------------------------------------------------------------
+// Helpers
+//-----------------------------------------------------------------------------
+
+/**
+ * Finds a rule with the given ID in the given config.
+ * @param {string} ruleId The ID of the rule to find.
+ * @param {Object} config The config to search in.
+ * @returns {{create: Function, schema: (Array|null)}} THe rule object.
+ */
+function findRuleDefinition(ruleId, config) {
+ const ruleIdParts = ruleId.split("/");
+ let pluginName, ruleName;
+
+ // built-in rule
+ if (ruleIdParts.length === 1) {
+ pluginName = "@";
+ ruleName = ruleIdParts[0];
+ } else {
+ ruleName = ruleIdParts.pop();
+ pluginName = ruleIdParts.join("/");
+ }
+
+ if (!config.plugins || !config.plugins[pluginName]) {
+ throw new TypeError(`Key "rules": Key "${ruleId}": Could not find plugin "${pluginName}".`);
+ }
+
+ if (!config.plugins[pluginName].rules || !config.plugins[pluginName].rules[ruleName]) {
+ throw new TypeError(`Key "rules": Key "${ruleId}": Could not find "${ruleName}" in plugin "${pluginName}".`);
+ }
+
+ return config.plugins[pluginName].rules[ruleName];
+
+}
+
+/**
+ * Gets a complete options schema for a rule.
+ * @param {{create: Function, schema: (Array|null)}} rule A new-style rule object
+ * @returns {Object} JSON Schema for the rule's options.
+ */
+function getRuleOptionsSchema(rule) {
+
+ if (!rule) {
+ return null;
+ }
+
+ const schema = rule.schema || rule.meta && rule.meta.schema;
+
+ if (Array.isArray(schema)) {
+ if (schema.length) {
+ return {
+ type: "array",
+ items: schema,
+ minItems: 0,
+ maxItems: schema.length
+ };
+ }
+ return {
+ type: "array",
+ minItems: 0,
+ maxItems: 0
+ };
+
+ }
+
+ // Given a full schema, leave it alone
+ return schema || null;
+}
+
+//-----------------------------------------------------------------------------
+// Exports
+//-----------------------------------------------------------------------------
+
+/**
+ * Implements validation functionality for the rules portion of a config.
+ */
+class RuleValidator {
+
+ /**
+ * Creates a new instance.
+ */
+ constructor() {
+
+ /**
+ * A collection of compiled validators for rules that have already
+ * been validated.
+ * @type {WeakMap}
+ * @property validators
+ */
+ this.validators = new WeakMap();
+ }
+
+ /**
+ * Validates all of the rule configurations in a config against each
+ * rule's schema.
+ * @param {Object} config The full config to validate. This object must
+ * contain both the rules section and the plugins section.
+ * @returns {void}
+ * @throws {Error} If a rule's configuration does not match its schema.
+ */
+ validate(config) {
+
+ if (!config.rules) {
+ return;
+ }
+
+ for (const [ruleId, ruleOptions] of Object.entries(config.rules)) {
+
+ // check for edge case
+ if (ruleId === "__proto__") {
+ continue;
+ }
+
+ /*
+ * If a rule is disabled, we don't do any validation. This allows
+ * users to safely set any value to 0 or "off" without worrying
+ * that it will cause a validation error.
+ *
+ * Note: ruleOptions is always an array at this point because
+ * this validation occurs after FlatConfigArray has merged and
+ * normalized values.
+ */
+ if (ruleOptions[0] === 0) {
+ continue;
+ }
+
+ const rule = findRuleDefinition(ruleId, config);
+
+ // Precompile and cache validator the first time
+ if (!this.validators.has(rule)) {
+ const schema = getRuleOptionsSchema(rule);
+
+ if (schema) {
+ this.validators.set(rule, ajv.compile(schema));
+ }
+ }
+
+ const validateRule = this.validators.get(rule);
+
+ if (validateRule) {
+
+ validateRule(ruleOptions.slice(1));
+
+ if (validateRule.errors) {
+ throw new Error(`Key "rules": Key "${ruleId}": ${
+ validateRule.errors.map(
+ error => `\tValue ${JSON.stringify(error.data)} ${error.message}.\n`
+ ).join("")
+ }`);
+ }
+ }
+ }
+ }
+}
+
+exports.RuleValidator = RuleValidator;