bun.sh/test/js/web/structured-clone-fastpath.test.ts

import { describe, expect, test } from "bun:test";

describe("Structured Clone Fast Path", () => {
  test("structuredClone should work with empty object", () => {
    const object = {};
    const cloned = structuredClone(object);
    expect(cloned).toStrictEqual({});
  });

  test("structuredClone should work with empty string", () => {
    const string = "";
    const cloned = structuredClone(string);
    expect(cloned).toStrictEqual("");
  });

  const deOptimizations = [
    {
      get accessor() {
        return 1;
      },
    },
    Object.create(Object.prototype, {
      data: {
        value: 1,
        writable: false,
        configurable: false,
      },
    }),
    Object.create(Object.prototype, {
      data: {
        value: 1,
        writable: true,
        configurable: false,
      },
    }),
    Object.create(Object.prototype, {
      data: {
        get: () => 1,
        configurable: true,
      },
    }),
    Object.create(Object.prototype, {
      data: {
        set: () => {},
        enumerable: true,
        configurable: true,
      },
    }),
  ];

  for (const deOptimization of deOptimizations) {
    test("structuredCloneDeOptimization", () => {
      structuredClone(deOptimization);
    });
  }

  test("structuredClone should use a constant amount of memory for string inputs", () => {
    const clones: Array<string> = [];
    // Create a 512KB string to test fast path
    const largeString = Buffer.alloc(512 * 1024, "a").toString();
    for (let i = 0; i < 100; i++) {
      clones.push(structuredClone(largeString));
    }
    Bun.gc(true);
    const rss = process.memoryUsage.rss();
    for (let i = 0; i < 10000; i++) {
      clones.push(structuredClone(largeString));
    }
    Bun.gc(true);
    const rss2 = process.memoryUsage.rss();
    const delta = rss2 - rss;
    expect(delta).toBeLessThan(1024 * 1024 * 8);
    expect(clones.length).toBe(10000 + 100);
  });

  test("structuredClone should use a constant amount of memory for simple object inputs", () => {
    // Create a 512KB string to test fast path
    const largeValue = { property: Buffer.alloc(512 * 1024, "a").toString() };
    for (let i = 0; i < 100; i++) {
      structuredClone(largeValue);
    }
    Bun.gc(true);
    const rss = process.memoryUsage.rss();
    for (let i = 0; i < 10000; i++) {
      structuredClone(largeValue);
    }
    Bun.gc(true);
    const rss2 = process.memoryUsage.rss();
    const delta = rss2 - rss;
    expect(delta).toBeLessThan(1024 * 1024);
  });

  test("structuredClone on object with simple properties can exceed JSFinalObject::maxInlineCapacity", () => {
    let largeValue = {};
    for (let i = 0; i < 100; i++) {
      largeValue["property" + i] = i;
    }

    for (let i = 0; i < 100; i++) {
      expect(structuredClone(largeValue)).toStrictEqual(largeValue);
    }
    Bun.gc(true);
    for (let i = 0; i < 100; i++) {
      expect(structuredClone(largeValue)).toStrictEqual(largeValue);
    }
  });
});