Update checked-in dependencies

node_modules/eslint/lib/config/flat-config-schema.js

@@ -53,6 +53,15 @@ function isNonNullObject(value) {
     return typeof value === "object" && value !== null;
 }
 
+/**
+ * Check if a value is a non-null non-array object.
+ * @param {any} value The value to check.
+ * @returns {boolean} `true` if the value is a non-null non-array object.
+ */
+function isNonArrayObject(value) {
+    return isNonNullObject(value) && !Array.isArray(value);
+}
+
 /**
  * Check if a value is undefined.
  * @param {any} value The value to check.
@@ -63,19 +72,27 @@ function isUndefined(value) {
 }
 
 /**
- * Deeply merges two objects.
+ * Deeply merges two non-array objects.
  * @param {Object} first The base object.
  * @param {Object} second The overrides object.
+ * @param {Map<string, Map<string, Object>>} [mergeMap] Maps the combination of first and second arguments to a merged result.
  * @returns {Object} An object with properties from both first and second.
  */
-function deepMerge(first = {}, second = {}) {
+function deepMerge(first, second, mergeMap = new Map()) {
 
-    /*
-     * If the second value is an array, just return it. We don't merge
-     * arrays because order matters and we can't know the correct order.
-     */
-    if (Array.isArray(second)) {
-        return second;
+    let secondMergeMap = mergeMap.get(first);
+
+    if (secondMergeMap) {
+        const result = secondMergeMap.get(second);
+
+        if (result) {
+
+            // If this combination of first and second arguments has been already visited, return the previously created result.
+            return result;
+        }
+    } else {
+        secondMergeMap = new Map();
+        mergeMap.set(first, secondMergeMap);
     }
 
     /*
@@ -89,27 +106,25 @@ function deepMerge(first = {}, second = {}) {
         ...second
     };
 
+    delete result.__proto__; // eslint-disable-line no-proto -- don't merge own property "__proto__"
+
+    // Store the pending result for this combination of first and second arguments.
+    secondMergeMap.set(second, result);
+
     for (const key of Object.keys(second)) {
 
         // avoid hairy edge case
-        if (key === "__proto__") {
+        if (key === "__proto__" || !Object.prototype.propertyIsEnumerable.call(first, key)) {
             continue;
         }
 
         const firstValue = first[key];
         const secondValue = second[key];
 
-        if (isNonNullObject(firstValue)) {
-            result[key] = deepMerge(firstValue, secondValue);
-        } else if (isUndefined(firstValue)) {
-            if (isNonNullObject(secondValue)) {
-                result[key] = deepMerge(
-                    Array.isArray(secondValue) ? [] : {},
-                    secondValue
-                );
-            } else if (!isUndefined(secondValue)) {
-                result[key] = secondValue;
-            }
+        if (isNonArrayObject(firstValue) && isNonArrayObject(secondValue)) {
+            result[key] = deepMerge(firstValue, secondValue, mergeMap);
+        } else if (isUndefined(secondValue)) {
+            result[key] = firstValue;
         }
     }