assert,util: improve array comparison

Sparse arrays and arrays containing undefined are now compared faster
using assert.deepStrictEqual() or util.isDeepStrictEqual().

Author: BridgeAR

benchmark/assert/deepequal-simple-array-and-set.js

@@ -11,6 +11,8 @@ const bench = common.createBenchmark(main, {
   method: [
     'deepEqual_Array',
     'notDeepEqual_Array',
+    'deepEqual_sparseArray',
+    'notDeepEqual_sparseArray',
     'deepEqual_Set',
     'notDeepEqual_Set',
   ],
@@ -25,18 +27,30 @@ function run(fn, n, actual, expected) {
 }
 
 function main({ n, len, method, strict }) {
-  const actual = [];
-  const expected = [];
+  let actual = Array.from({ length: len }, (_, i) => i);
+  // Contain one undefined value to trigger a specific code path
+  actual[0] = undefined;
+  let expected = actual.slice(0);
 
-  for (let i = 0; i < len; i++) {
-    actual.push(i);
-    expected.push(i);
-  }
   if (method.includes('not')) {
     expected[len - 1] += 1;
   }
 
   switch (method) {
+    case 'deepEqual_sparseArray':
+    case 'notDeepEqual_sparseArray':
+      actual = new Array(len);
+      for (let i = 0; i < len; i += 2) {
+        actual[i] = i;
+      }
+      expected = actual.slice(0);
+      if (method.includes('not')) {
+        expected[len - 2] += 1;
+        run(strict ? notDeepStrictEqual : notDeepEqual, n, actual, expected);
+      } else {
+        run(strict ? deepStrictEqual : deepEqual, n, actual, expected);
+      }
+      break;
     case 'deepEqual_Array':
       run(strict ? deepStrictEqual : deepEqual, n, actual, expected);
       break;

lib/internal/assert/myers_diff.js

@@ -29,6 +29,7 @@ function myersDiff(actual, expected, checkCommaDisparity = false) {
   const actualLength = actual.length;
   const expectedLength = expected.length;
   const max = actualLength + expectedLength;
+  // TODO(BridgeAR): Cap the input in case the values go beyond the limit of 2^31 - 1.
   const v = new Int32Array(2 * max + 1);
   const trace = [];
 

lib/internal/util/comparisons.js

@@ -196,11 +196,9 @@ function innerDeepEqual(val1, val2, mode, memos) {
     }
   } else {
     if (val1 === null || typeof val1 !== 'object') {
-      if (val2 === null || typeof val2 !== 'object') {
-        // eslint-disable-next-line eqeqeq
-        return val1 == val2 || (NumberIsNaN(val1) && NumberIsNaN(val2));
-      }
-      return false;
+      return (val2 === null || typeof val2 !== 'object') &&
+             // eslint-disable-next-line eqeqeq
+             (val1 == val2 || (NumberIsNaN(val1) && NumberIsNaN(val2)));
     }
     if (val2 === null || typeof val2 !== 'object') {
       return false;
@@ -384,9 +382,7 @@ function keyCheck(val1, val2, mode, memos, iterationType, keys2) {
       }
     } else if (keys2.length !== ObjectKeys(val1).length) {
       return false;
-    }
-
-    if (mode === kStrict) {
+    } else if (mode === kStrict) {
       const symbolKeysA = getOwnSymbols(val1);
       if (symbolKeysA.length !== 0) {
         let count = 0;
@@ -758,9 +754,9 @@ function sparseArrayEquiv(a, b, mode, memos, i) {
   if (keysA.length !== keysB.length) {
     return false;
   }
-  for (; i < keysA.length; i++) {
-    const key = keysA[i];
-    if (!hasOwn(b, key) || !innerDeepEqual(a[key], b[key], mode, memos)) {
+  for (; i < keysB.length; i++) {
+    const key = keysB[i];
+    if ((a[key] === undefined && !hasOwn(a, key)) || !innerDeepEqual(a[key], b[key], mode, memos)) {
       return false;
     }
   }
@@ -782,17 +778,14 @@ function objEquiv(a, b, mode, keys2, memos, iterationType) {
       return partialArrayEquiv(a, b, mode, memos);
     }
     for (let i = 0; i < a.length; i++) {
-      if (!innerDeepEqual(a[i], b[i], mode, memos)) {
-        return false;
-      }
-      const isSparseA = a[i] === undefined && !hasOwn(a, i);
-      const isSparseB = b[i] === undefined && !hasOwn(b, i);
-      if (isSparseA !== isSparseB) {
+      if (b[i] === undefined) {
+        if (!hasOwn(b, i))
+          return sparseArrayEquiv(a, b, mode, memos, i);
+        if (a[i] !== undefined || !hasOwn(a, i))
+          return false;
+      } else if (a[i] === undefined || !innerDeepEqual(a[i], b[i], mode, memos)) {
         return false;
       }
-      if (isSparseA) {
-        return sparseArrayEquiv(a, b, mode, memos, i);
-      }
     }
   } else if (iterationType === kIsSet) {
     if (!setEquiv(a, b, mode, memos)) {