From 7174dc2e8a5f4486ebc795eb06a184b1bf7445b1 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Sat, 19 Aug 2017 02:47:27 -0300
Subject: [PATCH] assert: handle sparse arrays in deepStrictEqual
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Detect sparse array ends and add a fail early path for
unequal array length.

PR-URL: https://github.com/nodejs/node/pull/15027
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
---
 lib/assert.js                     | 9 ++++++++-
 test/parallel/test-assert-deep.js | 3 +++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/lib/assert.js b/lib/assert.js
index 6e4b9effbe5549..e120a981346640 100644
--- 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
index c240d1a33efd9f..068950a33d3c39 100644
--- 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 */