feat: merge rule.meta.defaultOptions before validation

lib/shared/config-validator.js

@@ -19,6 +19,7 @@ import util from "util";
 import * as ConfigOps from "./config-ops.js";
 import { emitDeprecationWarning } from "./deprecation-warnings.js";
 import ajvOrig from "./ajv.js";
+import { deepMergeArrays } from "./deep-merge-arrays.js";
 import configSchema from "../../conf/config-schema.js";
 import BuiltInEnvironments from "../../conf/environments.js";
 
@@ -148,7 +149,10 @@ export default class ConfigValidator {
         const validateRule = ruleValidators.get(rule);
 
         if (validateRule) {
-            validateRule(localOptions);
+            const mergedOptions = deepMergeArrays(rule.meta?.defaultOptions, localOptions);
+
+            validateRule(mergedOptions);
+
             if (validateRule.errors) {
                 throw new Error(validateRule.errors.map(
                     error => `\tValue ${JSON.stringify(error.data)} ${error.message}.\n`

lib/shared/deep-merge-arrays.js

@@ -0,0 +1,58 @@
+/**
+ * @fileoverview Applies default rule options
+ * @author JoshuaKGoldberg
+ */
+
+/**
+ * Check if the variable contains an object strictly rejecting arrays
+ * @param {unknown} value an object
+ * @returns {boolean} Whether value is an object
+ */
+function isObjectNotArray(value) {
+    return typeof value === "object" && value !== null && value !== void 0 && !Array.isArray(value);
+}
+
+/**
+ * Deeply merges second on top of first, creating a new {} object if needed.
+ * @param {T} first Base, default value.
+ * @param {U} second User-specified value.
+ * @returns {T | U | (T & U)} Merged equivalent of second on top of first.
+ */
+function deepMergeObjects(first, second) {
+    if (second === void 0) {
+        return first;
+    }
+
+    if (!isObjectNotArray(first) || !isObjectNotArray(second)) {
+        return second;
+    }
+
+    const result = { ...first, ...second };
+
+    for (const key of Object.keys(second)) {
+        if (Object.prototype.propertyIsEnumerable.call(first, key)) {
+            result[key] = deepMergeObjects(first[key], second[key]);
+        }
+    }
+
+    return result;
+}
+
+/**
+ * Deeply merges second on top of first, creating a new [] array if needed.
+ * @param {T[]} first Base, default values.
+ * @param {U[]} second User-specified values.
+ * @returns {(T | U | (T & U))[]} Merged equivalent of second on top of first.
+ */
+function deepMergeArrays(first, second) {
+    if (!first || !second) {
+        return second || first || [];
+    }
+
+    return [
+        ...first.map((value, i) => deepMergeObjects(value, i < second.length ? second[i] : void 0)),
+        ...second.slice(first.length)
+    ];
+}
+
+export { deepMergeArrays };

tests/lib/shared/config-validator.js

@@ -73,6 +73,21 @@ const mockInvalidJSONSchemaRule = {
     }
 };
 
+const mockMaxPropertiesSchema = {
+    meta: {
+        defaultOptions: [{
+            foo: 42
+        }],
+        schema: [{
+            type: "object",
+            maxProperties: 2
+        }]
+    },
+    create() {
+        return {};
+    }
+};
+
 //------------------------------------------------------------------------------
 // Tests
 //------------------------------------------------------------------------------
@@ -253,4 +268,19 @@ describe("ConfigValidator", () => {
         });
 
     });
+
+    describe("validateRuleSchema", () => {
+
+        it("should throw when rule options are invalid after defaults are applied", () => {
+            const fn = validator.validateRuleSchema.bind(validator, mockMaxPropertiesSchema, [{ bar: 6, baz: 7 }]);
+
+            nodeAssert.throws(
+                fn,
+                {
+                    message: '\tValue {"foo":42,"bar":6,"baz":7} should NOT have more than 2 properties.\n'
+                }
+            );
+        });
+
+    });
 });

tests/lib/shared/deep-merge-arrays.js

@@ -0,0 +1,138 @@
+/* eslint-disable no-undefined -- `null` and `undefined` are different in options */
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+import assert from "node:assert";
+
+import { deepMergeArrays } from "../../../lib/shared/deep-merge-arrays.js";
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+/**
+ * Turns a value into its string equivalent for a test name.
+ * @param {unknown} value Value to be stringified.
+ * @returns {string} String equivalent of the value.
+ */
+function toTestCaseName(value) {
+    return typeof value === "object" ? JSON.stringify(value) : `${value}`;
+}
+
+describe("deepMerge", () => {
+    for (const [first, second, result] of [
+        [undefined, undefined, []],
+        [[], undefined, []],
+        [["abc"], undefined, ["abc"]],
+        [undefined, ["abc"], ["abc"]],
+        [[], ["abc"], ["abc"]],
+        [[undefined], ["abc"], ["abc"]],
+        [[undefined, undefined], ["abc"], ["abc", undefined]],
+        [[undefined, undefined], ["abc", "def"], ["abc", "def"]],
+        [[undefined, null], ["abc"], ["abc", null]],
+        [[undefined, null], ["abc", "def"], ["abc", "def"]],
+        [[null], ["abc"], ["abc"]],
+        [[123], [undefined], [123]],
+        [[123], [null], [null]],
+        [[123], [{ a: 0 }], [{ a: 0 }]],
+        [["abc"], [undefined], ["abc"]],
+        [["abc"], [null], [null]],
+        [["abc"], ["def"], ["def"]],
+        [["abc"], [{ a: 0 }], [{ a: 0 }]],
+        [[["abc"]], [null], [null]],
+        [[["abc"]], ["def"], ["def"]],
+        [[["abc"]], [{ a: 0 }], [{ a: 0 }]],
+        [[{ abc: true }], ["def"], ["def"]],
+        [[{ abc: true }], [["def"]], [["def"]]],
+        [[null], [{ abc: true }], [{ abc: true }]],
+        [[{ a: undefined }], [{ a: 0 }], [{ a: 0 }]],
+        [[{ a: null }], [{ a: 0 }], [{ a: 0 }]],
+        [[{ a: null }], [{ a: { b: 0 } }], [{ a: { b: 0 } }]],
+        [[{ a: 0 }], [{ a: 1 }], [{ a: 1 }]],
+        [[{ a: 0 }], [{ a: null }], [{ a: null }]],
+        [[{ a: 0 }], [{ a: undefined }], [{ a: 0 }]],
+        [[{ a: 0 }], ["abc"], ["abc"]],
+        [[{ a: 0 }], [123], [123]],
+        [[[{ a: 0 }]], [123], [123]],
+        [
+            [{ a: ["b"] }],
+            [{ a: ["c"] }],
+            [{ a: ["c"] }]
+        ],
+        [
+            [{ a: [{ b: "c" }] }],
+            [{ a: [{ d: "e" }] }],
+            [{ a: [{ d: "e" }] }]
+        ],
+        [
+            [{ a: { b: "c" }, d: true }],
+            [{ a: { e: "f" } }],
+            [{ a: { b: "c", e: "f" }, d: true }]
+        ],
+        [
+            [{ a: { b: "c" } }],
+            [{ a: { e: "f" }, d: true }],
+            [{ a: { b: "c", e: "f" }, d: true }]
+        ],
+        [
+            [{ a: { b: "c" } }, { d: true }],
+            [{ a: { e: "f" } }, { f: 123 }],
+            [{ a: { b: "c", e: "f" } }, { d: true, f: 123 }]
+        ],
+        [
+            [{ hasOwnProperty: true }],
+            [{}],
+            [{ hasOwnProperty: true }]
+        ],
+        [
+            [{ hasOwnProperty: false }],
+            [{}],
+            [{ hasOwnProperty: false }]
+        ],
+        [
+            [{ hasOwnProperty: null }],
+            [{}],
+            [{ hasOwnProperty: null }]
+        ],
+        [
+            [{ hasOwnProperty: undefined }],
+            [{}],
+            [{ hasOwnProperty: undefined }]
+        ],
+        [
+            [{}],
+            [{ hasOwnProperty: null }],
+            [{ hasOwnProperty: null }]
+        ],
+        [
+            [{}],
+            [{ hasOwnProperty: undefined }],
+            [{ hasOwnProperty: undefined }]
+        ],
+        [
+            [{
+                allow: [],
+                ignoreDestructuring: false,
+                ignoreGlobals: false,
+                ignoreImports: false,
+                properties: "always"
+            }],
+            [],
+            [{
+                allow: [],
+                ignoreDestructuring: false,
+                ignoreGlobals: false,
+                ignoreImports: false,
+                properties: "always"
+            }]
+        ]
+    ]) {
+        it(`${toTestCaseName(first)}, ${toTestCaseName(second)}`, () => {
+            assert.deepStrictEqual(deepMergeArrays(first, second), result);
+        });
+    }
+});
+
+/* eslint-enable no-undefined -- `null` and `undefined` are different in options */