JSON response with special chars truncated since 2.2.0

[LeBenLeBen]

Prerequisites

• I confirm my issue is not in the opened issues
• I confirm the Frequently Asked Questions didn't contain the answer to my issue

Environment check

• I'm using the latest msw version
• I'm using Node.js version 18 or higher

Node.js version

20.9.0

Reproduction repository

https://github.com/LeBenLeBen/msw-truncated

Reproduction steps

Clone the reproduction repo, then:

1. npm install
2. npm start
3. Visit http://localhost:7051/user

Current behavior

The JSON response is truncated a few characters before the end and cannot be parsed by the browser. It’s caused by the special char é in the response. The problem does not occur before MSW 2.2.0, so I’m guessing it’s a regression caused by #1658

Expected behavior

The JSON response should be complete.

[ZeroCho]

I left a comment in #1658 but as this is the same problem with mine, I'll copy it here.

I have an issue with 2.2.0+ version of MSW, when I put CJK(Chinese, Japanese, Korean character) in MSW response.
Until msw@2.1.0, it was fine. I checked out what was changed in 2.2.0, and I found this commit could be the problem.

For example, the length of string '조현영' (which is Korean) is 9 bytes in network, whereas 'abc' is 3 bytes. But both are 3 lengths in JavaScript. I think current implementation which calculate length by just string.length can be problem.
I think using new TextEncoder().encode(str).length would be better to calculate Content-Length. Thank you

[kettanaito]

Root cause

Right now, we are relying on the string length to determine the value of the automatic Content-Length response header.

Instead, we should convert the string to buffer and measure its byte length. There are a couple of ways to do that:

1. new TextEncoder().encode(text).byteLength
2. new Blob([text]).size

Pull requests are welcome! I'd start with a failing test for special characters right here:

msw/src/core/HttpResponse.test.ts

Line 16 in 23fc364

describe('HttpResponse.text()', () => {

[kettanaito]

Released: v2.2.2 🎉

This has been released in v2.2.2!

• 📄 Release notes
• 📦 npm package

Make sure to always update to the latest version (npm i msw@latest) to get the newest features and bug fixes.

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