Starting in 0.8 we can get: TypeError: useContext is not a function or its return value is not iterable

[bertbarabas]

Describe the bug

Forcing a recompile by just adding a blank line causes the exception below.

The exception never happened in 0.7.14

[Reflex Frontend Exception]
 TypeError: useContext is not a function or its return value is not iterable
    at http://localhost:3000/utils/components.jsx?t=1752717277114:67:38
    at react-stack-bottom-frame (http://localhost:3000/node_modules/.vite/deps/react-dom_client.js?v=03abd703:17424:20)
    at renderWithHooks (http://localhost:3000/node_modules/.vite/deps/react-dom_client.js?v=03abd703:4206:24)
    at updateFunctionComponent (http://localhost:3000/node_modules/.vite/deps/react-dom_client.js?v=03abd703:6619:21)
    at updateSimpleMemoComponent (http://localhost:3000/node_modules/.vite/deps/react-dom_client.js?v=03abd703:6528:16)
    at beginWork (http://localhost:3000/node_modules/.vite/deps/react-dom_client.js?v=03abd703:7923:20)
    at runWithFiberInDEV (http://localhost:3000/node_modules/.vite/deps/react-dom_client.js?v=03abd703:1485:72)
    at performUnitOfWork (http://localhost:3000/node_modules/.vite/deps/react-dom_client.js?v=03abd703:10868:98)
    at workLoopSync (http://localhost:3000/node_modules/.vite/deps/react-dom_client.js?v=03abd703:10728:43)
    at renderRootSync (http://localhost:3000/node_modules/.vite/deps/react-dom_client.js?v=03abd703:10711:13)

To Reproduce The error only ever happened in a large project and not when I tried to create a small test case from scratch. To get around that I started with my large project and kept removing stuff until the exception went away then restored the last remove and kept going with removing other stuff. Eventually I got down to the repo below which is valid but a bit non-sensical from a use perspective.

To reproduce:

1. Clone the repo
2. Setup venv and install requirements
3. Reflex run
4. Visit the web page
5. Go to a python file like application.py
6. Insert a blank line somewhere and wait for the recompile.
7. You should get an exception but if not keep trying adding or removing a line and waiting for recompile and see if the exception appears after the recompile. If it still doesn't happen try restarting the app and doing that again.

https://github.com/bertbarabas/test-reflex-regen#

Specifics (please complete the following information):

• Python Version: 3.12.3
• Reflex Version: 0.8.2
• OS: Ubuntu on WSL

*Additional context It seems unrelated to any specific component, perhaps it is timing related. For instance I include a dummy project db on neon. When reproducing the bug a closer region didn't cause the bug so maybe you have to cause some kind of latency to get the timing just right. But it's not just the db, if I removed the @memo it went away. So like I said I don't think it's related to a specific component and it's more likely to show up in larger projects.

[linear[bot]]

ENG-6727 Starting in 0.8 we can get: TypeError: useContext is not a function or its return value is not iterable

[masenf]

This issue occurs when vite hmr causes two different versions of React to be loaded in the browser. We're trying to find a way around it, but it's a bit lower level than what reflex generates/manages

[bertbarabas]

Hi @masenf, any luck with this one? It pretty much blocks development since it requires stopping reflex run and restarting after most changes...

[bertbarabas]

@masenf - Thinking about your point above that this exception is a problem with vite HMR,

I tried both env variables:

VITE_FORCE_FULL_RELOAD=1 VITE_HMR=0

But the useContext exception still happens...