assert: fix deepEqual RangeError: Maximum call stack size exceeded

Fixes: https://github.com/nodejs/node/issues/13314
Refs: https://github.com/nodejs/node/issues/6416

This commit changes semantics of the memos cycles tracker. Before
the change it was used to track all currently wisited nodes of an
object tree, which is a bit shifted from its original intention of
tracking cycles. The change brings intended semantics, by tracking
only objects of the current branch of the object tree.

PR-URL: https://github.com/nodejs/node/pull/13318
Fixes: https://github.com/nodejs/node/issues/13314
Ref: https://github.com/nodejs/node/issues/6416
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

1 files changed, 16 insertions, 13 deletions

diff --git a/lib/assert.js b/lib/assert.js
index 0f0f3f165a..5aca511194 100644
--- a/lib/assert.js
+++ b/lib/assert.js
@@ -262,24 +262,27 @@ function _deepEqual(actual, expected, strict, memos) {
   // Use memos to handle cycles.
   if (!memos) {
     memos = {
-      actual: { map: new Map(), position: 0 },
-      expected: { map: new Map(), position: 0 }
+      actual: new Map(),
+      expected: new Map(),
+      position: 0
     };
-  }
-
-  const actualPosition = memos.actual.map.get(actual);
-  if (actualPosition !== undefined) {
-    if (actualPosition === memos.expected.map.get(expected)) {
-      return true;
-    }
   } else {
-    memos.actual.map.set(actual, memos.actual.position++);
+    memos.position++;
   }
-  if (!memos.expected.map.has(expected)) {
-    memos.expected.map.set(expected, memos.expected.position++);
+
+  if (memos.actual.has(actual)) {
+    return memos.actual.get(actual) === memos.expected.get(expected);
   }
 
-  return objEquiv(actual, expected, strict, memos);
+  memos.actual.set(actual, memos.position);
+  memos.expected.set(expected, memos.position);
+
+  const areEq = objEquiv(actual, expected, strict, memos);
+
+  memos.actual.delete(actual);
+  memos.expected.delete(expected);
+
+  return areEq;
 }
 
 function setHasSimilarElement(set, val1, strict, memo) {