assert: improve myers diff performance

benchmark/assert/assertion-error.js

@@ -0,0 +1,38 @@
+'use strict';
+const common = require('../common.js');
+const assert = require('assert');
+
+const bench = common.createBenchmark(main, {
+ n: [10, 50, 200, 500],
+ size: [10, 100],
+ datasetName: ['objects'],
+});
+
+const baseObject = {
+ a: 1,
+ b: {
+ c: 2,
+ d: [3, 4, 5],
+ e: 'fghi',
+ j: {
+ k: 6,
+ },
+ },
+};
+
+function createObjects(size) {
+ return Array.from({ length: size }, () => baseObject);
+}
+
+function main({ n, size }) {
+ bench.start();
+ for (let i = 0; i < n; ++i) {
+ new assert.AssertionError({
+ actual: {},
+ expected: createObjects(size),
+ operator: 'partialDeepStrictEqual',
+ stackStartFunction: () => {},
+ });
+ }
+ bench.end(n);
+}

lib/internal/assert/myers_diff.js

@@ -2,7 +2,6 @@
 
 const {
  ArrayPrototypePush,
- ArrayPrototypeSlice,
  Int32Array,
  StringPrototypeEndsWith,
 } = primordials;
@@ -16,7 +15,7 @@ function areLinesEqual(actual, expected, checkCommaDisparity) {
  return true;
  }
  if (checkCommaDisparity) {
- return `${actual},` === expected || actual === `${expected},`;
+ return (actual + ',') === expected || actual === (expected + ',');
  }
  return false;
 }
@@ -26,12 +25,10 @@ function myersDiff(actual, expected, checkCommaDisparity = false) {
  const expectedLength = expected.length;
  const max = actualLength + expectedLength;
  const v = new Int32Array(2 * max + 1);
-
  const trace = [];
 
  for (let diffLevel = 0; diffLevel <= max; diffLevel++) {
- const newTrace = ArrayPrototypeSlice(v);
- ArrayPrototypePush(trace, newTrace);
+ ArrayPrototypePush(trace, new Int32Array(v)); // Clone the current state of `v`
 
  for (let diagonalIndex = -diffLevel; diagonalIndex <= diffLevel; diagonalIndex += 2) {
  const offset = diagonalIndex + max;
@@ -89,22 +86,17 @@ function backtrack(trace, actual, expected, checkCommaDisparity) {
 
  while (x > prevX && y > prevY) {
  const actualItem = actual[x - 1];
- const value =
- !checkCommaDisparity || StringPrototypeEndsWith(actualItem, ',') ?
- actualItem :
- expected[y - 1];
+ const value = checkCommaDisparity && !StringPrototypeEndsWith(actualItem, ',') ? expected[y - 1] : actualItem;
  ArrayPrototypePush(result, { __proto__: null, type: 'nop', value });
  x--;
  y--;
  }
 
  if (diffLevel > 0) {
  if (x > prevX) {
- ArrayPrototypePush(result, { __proto__: null, type: 'insert', value: actual[x - 1] });
- x--;
+ ArrayPrototypePush(result, { __proto__: null, type: 'insert', value: actual[--x] });
  } else {
- ArrayPrototypePush(result, { __proto__: null, type: 'delete', value: expected[y - 1] });
- y--;
+ ArrayPrototypePush(result, { __proto__: null, type: 'delete', value: expected[--y] });
  }
  }
  }