assert: handle sparse arrays in deepStrictEqual

Detect sparse array ends and add a fail early path for unequal array length. PR-URL: #15027 Reviewed-By: Rich Trott <[email protected]> Reviewed-By: Yuta Hiroto <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Tobias Nießen <[email protected]>
nodejs · Sep 12, 2017 · 7174dc2 · 7174dc2
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commit 7174dc2
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diff --git a/lib/assert.js b/lib/assert.js
@@ -178,7 +178,14 @@ function strictDeepEqual(actual, expected) {
   if (Object.getPrototypeOf(actual) !== Object.getPrototypeOf(expected)) {
     return false;
   }
-  if (isObjectOrArrayTag(actualTag)) {
+  if (actualTag === '[object Array]') {
+    // Check for sparse arrays and general fast path
+    if (actual.length !== expected.length)
+      return false;
+    // Skip testing the part below and continue in the callee function.
+    return;
+  }
+  if (actualTag === '[object Object]') {
     // Skip testing the part below and continue in the callee function.
     return;
   }

diff --git a/test/parallel/test-assert-deep.js b/test/parallel/test-assert-deep.js
@@ -404,4 +404,7 @@ assertOnlyDeepEqual(
   assertDeepAndStrictEqual(m3, m4);
 }
 
+assertDeepAndStrictEqual([1, , , 3], [1, , , 3]);
+assertOnlyDeepEqual([1, , , 3], [1, , , 3, , , ]);
+
 /* eslint-enable */