Detail of sveltejs/kit#13894 | Svelte Changelog

fix: Dumber fix for error assertions
#13894

Closing issue

Describe the bug

After upgrading to SvelteKit 2.21.5 from SvelteKit 2.21.2, I am starting to get ReferenceError: require is not defined in ES module scope whenever I import a package that uses require in any capacity. This did not happen before SvelteKit 2.21.3.

I thought it might be an issue with specific packages or projects, but it's not. I tested three different projects, all with different dependencies, and the same problem occurred.

Examples of affected packages:

marked (https://www.npmjs.com/package/marked)
highlight.js (https://www.npmjs.com/package/highlight.js)
@google/genai (https://www.npmjs.com/package/@google/genai)
nodemailer (https://www.npmjs.com/package/nodemailer)

I concluded that the issue is caused by SvelteKit versions >= 2.21.3 because I kept downgrading, and once I went below 2.21.3, things worked as expected.

Reproduction

Create a new SvelteKit project
Install one or more of the packages mentioned above
Import one or more of them in a server module (e.g. +page.server.ts, code inside a .server.ts file, or files inside the $lib/server directory)
Build your app
Run the app and execute any code that would cause the module to be loaded

Logs

ReferenceError: require is not defined in ES module scope, you can use import instead
This file is being treated as an ES module because it has a '.js' file extension and '[REDACTED_PATH]/package.json' contains "type": "module". To treat it as a CommonJS script, rename it to use the '.cjs' file extension.
    at ExportsCache.has (file://[REDACTED_PATH]/build/server/chunks/hooks.server-MojicEX3.js:15490:20)
    at Module.patchedRequire (file://[REDACTED_PATH]/build/server/chunks/hooks.server-MojicEX3.js:15618:22)
    at Hook._require.Module.require (file://[REDACTED_PATH]/build/server/chunks/hooks.server-MojicEX3.js:15557:28)
    at require (node:internal/modules/helpers:135:16)
    at Object.<anonymous> ([REDACTED_PATH]/node_modules/highlight.js/lib/index.js:1:12)
    at Module._compile (node:internal/modules/cjs/loader:1730:14)
    at Object..js (node:internal/modules/cjs/loader:1895:10)
    at Module.load (node:internal/modules/cjs/loader:1465:32)
    at Function._load (node:internal/modules/cjs/loader:1282:12)
    at TracingChannel.traceSync (node:diagnostics_channel:322:14)

System Info

System:
    OS: Windows 11 10.0.26100
    CPU: (28) x64 Intel(R) Core(TM) i7-14700K
    Memory: 35.78 GB / 63.70 GB
  Binaries:
    Node: 22.16.0 - C:\Program Files\nodejs\node.EXE
    npm: 11.4.1 - ~\AppData\Roaming\npm\npm.CMD
    bun: 1.2.16 - ~\.bun\bin\bun.EXE
  Browsers:
    Edge: Chromium (137.0.3296.68)
    Internet Explorer: 11.0.26100.1882
  npmPackages:
    @sveltejs/adapter-node: ^5.2.12 => 5.2.12
    @sveltejs/kit: ^2.21.5 => 2.21.5
    @sveltejs/vite-plugin-svelte: ^5.1.0 => 5.1.0
    svelte: ^5.34.2 => 5.34.2
    vite: ^6.3.5 => 6.3.5

Severity

blocking an upgrade

Additional Information

No response

👍 6

Open #13888 on GitHub

Pull request

Closed

elliott-with-the-longest-name-on-github Jun 17, 2025, 12:17 AM

fixes #13888

We've had issues in the past because isHttpError, isRedirect, and isActionFailure can start reporting false negatives when something somewhere decides to load two copies of the modules the classes are declared in. This switches to a tagged, structural approach that will survive these boundaries. The downside is that some library could throw { _tag: 'SvelteKitRedirect' } and isRedirect would report true, but... I mean, at that point, "hack the library at your own peril", I guess.

This would let us revert our prior attempt at externalizing dependencies, which has caused additional bugs.

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
This message body should clearly illustrate what problems it solves.
Ideally, include a test that fails without this PR but passes with it.

Tests

Run the tests with pnpm test and lint the project with pnpm lint and pnpm check

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Info

Closed at Jul 9, 2025, 12:26 PM

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