Issue with WeakMap and Proxy in Vite's Hot Module Replacement (HMR)

[ltxhhz]

Describe the bug

Hello Vite team,

I’ve encountered an issue when using Vite's Hot Module Replacement (HMR) with libraries(@tonejs/midi src/Note.ts:87) that store instance-specific data in a WeakMap. It appears that HMR wraps modules in a Proxy for hot reloading, and this leads to problems with WeakMap when accessing values based on this.

Here’s the problem:

• In a class, I store instance-specific data using WeakMap.set(this, value).
• When the class instance is proxied by Vite (due to HMR), the proxy object and the original object are treated as different references.
• This causes issues because the proxy object does not match the original object stored in the WeakMap, and as a result, I cannot retrieve the value correctly from the WeakMap after the module is hot-reloaded.

Expected behavior:

I expect the class to retrieve the value correctly from the WeakMap, regardless of whether it is proxied by Vite’s HMR.

Actual behavior:

The value is not retrievable from the WeakMap after HMR because the this in the class and the proxy object are not the same reference.

Possible solutions:

• One possible solution would be to provide an option to disable Proxy wrapping for certain modules or instances during HMR.
• Another solution could involve providing a way to access the original instance even when it is wrapped in a proxy.

This issue may affect other libraries(e.g. @tonejs/midi src/Note.ts:87) that rely on WeakMap for instance-specific data storage and is related to how HMR interacts with Proxy.

Thank you for your time, and I appreciate any guidance or potential solutions to this issue!

Reproduction

https://stackblitz.com/edit/vitejs-vite-remkcupg?file=src%2Fmain.js

Steps to reproduce

1. Create a class that stores instance-specific data in a WeakMap using this as the key.
2. Use Vite for development with HMR enabled.
3. Access the value stored in the WeakMap after the module is hot-reloaded.

System Info

System:
    OS: Windows 11 10.0.22631
    CPU: (16) x64 AMD Ryzen 7 7735H with Radeon Graphics
    Memory: 6.79 GB / 27.69 GB
  Binaries:
    Node: 18.20.4 - d:\Program Files\nodejs\node.EXE
    Yarn: 4.3.0 - D:\node_global\yarn.CMD
    npm: 10.9.1 - d:\Program Files\nodejs\npm.CMD
    pnpm: 9.15.0 - ~\AppData\Local\pnpm\pnpm.CMD
    bun: 1.1.26 - D:\node_global\bun.CMD
  npmPackages:
    @vitejs/plugin-vue: ^5.2.1 => 5.2.1
    vite: ^6.0.7 => 6.0.7

Used Package Manager

pnpm

Logs

No response

Validations

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• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to vuejs/core instead.
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• The provided reproduction is a minimal reproducible example of the bug.

[ltxhhz]

Closed because I can't confirm if the issue is vite related or not.