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Using debug package causes bug with turbopack and @svgr/webpack #78804

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paul-vd opened this issue May 3, 2025 · 4 comments · May be fixed by #78962
Open

Using debug package causes bug with turbopack and @svgr/webpack #78804

paul-vd opened this issue May 3, 2025 · 4 comments · May be fixed by #78962
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linear: turbopack Confirmed issue that is tracked by the Turbopack team. Turbopack Related to Turbopack with Next.js.

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@paul-vd
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paul-vd commented May 3, 2025

Link to the code that reproduces this issue

https://github.com/paul-vd/nextjs-debug-reproduction

To Reproduce

  1. Ensure you have a .env with DEBUG="acme*" (acme can be anything)
  2. Start the application bun run dev
  3. Open http://localhost:3000

Current vs. Expected behavior

I expected to see the next.js logo, but I observed the following error instead:

 ⨯ ./app/next.svg
Error evaluating Node.js code
TypeError: 'process.env' only accepts a configurable, writable, and enumerable data descriptor
    [at Function.save (/private/tmp/reproduction-app/node_modules/debug/src/node.js:205:21)]
    [at Function.enable (/private/tmp/reproduction-app/node_modules/debug/src/common.js:163:15)]
    [at setup (/private/tmp/reproduction-app/node_modules/debug/src/common.js:287:14)]
    [at Object.<anonymous> (/private/tmp/reproduction-app/node_modules/debug/src/node.js:240:37)]
    [at Module._compile (node:internal/modules/cjs/loader:1562:14)]
    [at Object..js (node:internal/modules/cjs/loader:1699:10)]
    [at Module.load (node:internal/modules/cjs/loader:1313:32)]
    [at Function._load (node:internal/modules/cjs/loader:1123:12)]
    [at TracingChannel.traceSync (node:diagnostics_channel:322:14)]
    [at wrapModuleLoad (node:internal/modules/cjs/loader:217:24)]



./app/page.tsx:1:1
Export default doesn't exist in target module
> 1 | import NextLogo from "./next.svg";
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  2 | export default function Home() {
  3 |   return (
  4 |     <div>

The export default was not found in module [project]/app/next.svg.js [app-rsc] (ecmascript).
The module has no exports at all.
All exports of the module are statically known (It doesn't have dynamic exports). So it's known statically that the requested export doesn't exist.

 ○ Compiling /_error ...
 ✓ Compiled /_error in 931ms
 GET / 500 in 4004ms
 ✓ Compiled /favicon.ico in 470ms
 GET /favicon.ico 500 in 524ms

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.4.0: Fri Apr 11 18:33:47 PDT 2025; root:xnu-11417.101.15~117/RELEASE_ARM64_T6000
  Available memory (MB): 16384
  Available CPU cores: 8
Binaries:
  Node: 22.13.1
  npm: 10.9.2
  Yarn: 1.22.22
  pnpm: 8.8.0
Relevant Packages:
  next: 15.4.0-canary.19 // Latest available version is detected (15.4.0-canary.19).
  eslint-config-next: N/A
  react: 19.1.0
  react-dom: 19.1.0
  typescript: 5.8.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Turbopack

Which stage(s) are affected? (Select all that apply)

next dev (local)

Additional context

I have also tested without installing the debug, but the same issue occurs, I believe it might be a peer of other depenencies, from lock file:

  • @babel/traverse
  • @babel/helper-define-polyfill-provider
@github-actions github-actions bot added the Turbopack Related to Turbopack with Next.js. label May 3, 2025
@timneutkens
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Used the reproduction to create a more minimal reproduction that highlights the Node.js error:

// custom-loader.js
module.exports = (source) => {
  process.env.TEST_THIS_THING = "def";

  return "export default () => null";
};

// next.config.ts
import type { NextConfig } from "next";
import { join } from "path";

const nextConfig: NextConfig = {
  /* config options here */
  reactStrictMode: true,
  turbopack: {
    rules: {
      "*.svg": {
        as: "*.js",
        loaders: [join(__dirname, "./custom-loader.js")],
      },
    },
  },
};

export default nextConfig;

TEST_THIS_THING=abc next dev --turbopack

It seems to only happen when trying to assign values to an env var that was already set before.

@timneutkens
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Seems the root cause is here where process.env is turned into a proxy for webpack loaders:

next.js/turbopack/crates/turbopack-node/js/src/transforms/webpack-loaders.ts

Line 159 in dbb3d14

process.env = new Proxy(originalEnv, {

@timneutkens
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Verified it's indeed caused by that Proxy, even smaller reproduction in isolation:

// testthis.js
// Patch process.env to track which env vars are read
const originalEnv = process.env
const readEnvVars = new Set()
process.env = new Proxy(originalEnv, {
  get(target, prop) {
    if (typeof prop === 'string' && !readEnvVars.has(prop)) {
      // We register the env var as dependency on the
      // current transform and all future transforms
      // since the env var might be cached in module scope
      // and influence them all
      readEnvVars.add(prop)
    }
    return Reflect.get(target, prop)
  },
})

process.env.TEST_THIS_THING = 'def'

TEST_THIS_THING=abc node testthis.js        
/Users/timneutkens/projects/next.js/testthis.js:17
process.env.TEST_THIS_THING = 'def'
                            ^

TypeError: 'process.env' only accepts a configurable, writable, and enumerable data descriptor
    at Object.<anonymous> (/Users/timneutkens/projects/next.js/testthis.js:17:29)
    at Module._compile (node:internal/modules/cjs/loader:1364:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1422:10)
    at Module.load (node:internal/modules/cjs/loader:1203:32)
    at Module._load (node:internal/modules/cjs/loader:1019:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:128:12)
    at node:internal/main/run_main_module:28:49 {
  code: 'ERR_INVALID_OBJECT_DEFINE_PROPERTY'
}

Node.js v18.20.6

TEST_THIS_THING=abc node testthis.js

@timneutkens timneutkens added the linear: turbopack Confirmed issue that is tracked by the Turbopack team. label May 8, 2025
@timneutkens timneutkens linked a pull request May 8, 2025 that will close this issue
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@timneutkens
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Fixed the problem in #78962. Thanks for the reproduction! Very helpful 🙏

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Turbopack: Fix setting existing env var in webpack loader vercel/next.js
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