assert: fix deepEqual inconsistencies

PR-URL: https://github.com/nodejs/node/pull/14491
Fixes: https://github.com/nodejs/node/issues/14441
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Khaidi Chu <i@2333.moe>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

lib/assert.js

@@ -271,8 +271,15 @@ function innerDeepEqual(actual, expected, strict, memos) {
       position: 0
     };
   } else {
-    if (memos.actual.has(actual)) {
+    // We prevent up to two map.has(x) calls by directly retrieving the value
-      return memos.actual.get(actual) === memos.expected.get(expected);
+    // and checking for undefined. The map can only contain numbers, so it is
+    // safe to check for undefined only.
+    const expectedMemoA = memos.actual.get(actual);
+    if (expectedMemoA !== undefined) {
+      const expectedMemoB = memos.expected.get(expected);
+      if (expectedMemoB !== undefined) {
+        return expectedMemoA === expectedMemoB;
+      }
     }
     memos.position++;
   }

test/parallel/test-assert-deep.js

@@ -303,6 +303,26 @@ assertOnlyDeepEqual(
   new Set([undefined])
 );
 
+// Circular structures
+{
+  const a = {};
+  const b = {};
+  a.a = a;
+  b.a = {};
+  b.a.a = a;
+  assertDeepAndStrictEqual(a, b);
+}
+
+{
+  const a = new Set();
+  const b = new Set();
+  const c = new Set();
+  a.add(a);
+  b.add(b);
+  c.add(a);
+  assertDeepAndStrictEqual(b, c);
+}
+
 {
   const values = [
     123,

test/parallel/test-assert.js

@@ -578,8 +578,8 @@ a.throws(makeBlock(thrower, TypeError), function(err) {
 
   const h = { ref: g };
 
-  a.throws(makeBlock(a.deepEqual, f, h), /AssertionError/);
+  a.doesNotThrow(makeBlock(a.deepEqual, f, h));
-  a.throws(makeBlock(a.deepStrictEqual, f, h), /AssertionError/);
+  a.doesNotThrow(makeBlock(a.deepStrictEqual, f, h));
 }
 // GH-7178. Ensure reflexivity of deepEqual with `arguments` objects.
 const args = (function() { return arguments; })();