Sample 34 test breaks with superjson 2.2.3 due to exact JSON matching

[mag123c]

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

Summary
Sample 34 (sample/34-using-esm-packages) E2E test fails with superjson 2.2.3

Error Message
expected '{"jsonString":"{"json":{"big":"10"},"meta":{"values":{"big":["bigint"]}}}"}'
got '{"jsonString":"{"json":{"big":"10"},"meta":{"values":{"big":["bigint"]},"v":1}}"}'

superjson 2.2.3 was published to npm on Oct 22, 2025 (06:20 UTC), and CI tests started failing immediately after. The package added a "v": 1 field to the meta object for backward compatibility

Context

• Sample 34 demonstrates how to import and use ESM-only packages in a CommonJS
  NestJS project (Node 18.8+)
• Uses superjson as an example ESM package
• superjson 2.2.3 added a "v": 1 field to the meta object (PR A way to create own console commands #311)
• Test uses exact JSON string matching, making it fragile to format changes

Minimum reproduction code

https://github.com/nestjs/nest/tree/master/sample/34-using-esm-packages

Steps to reproduce

1. cd sample/34-using-esm-packages
2. npm install (installs superjson 2.2.3 due to "superjson": "2.x")
3. npm run test:e2e
4. Test fails

Expected behavior

• ESM package is successfully imported
• ESM package functions correctly
• NOT verify superjson's internal serialization format

Better approach example

.expect((res) => {
  const result = JSON.parse(res.body.jsonString);
  expect(result.json.big).toBe('10');
  expect(result.meta.values.big).toEqual(['bigint']);
});

NestJS version

11.1.7

Packages versions

{
  "@nestjs/common": "11.x",
  "@nestjs/core": "11.x",
  "@nestjs/platform-express": "11.x",
  "superjson": "2.x"
}

Node.js version

18.8+

In which operating systems have you tested?

• macOS
• Windows
• Linux

Other

Purpose of Sample 34 is demonstrates importing ESM-only packages in CommonJS NestJS projects using Node 18.8+'s --experimental-vm-modules flag with dynamic imports.

Related

• superjson issue: Input mapping is buggy flightcontrolhq/superjson#310
• superjson PR: fix: input escape mapping flightcontrolhq/superjson#311

Proposed solutions

1. Fix test to be format-agnostic (recommended)
2. Pin superjson to 2.2.2
3. Update expected output to include "v": 1