HMR confuses global signals

[rjvdw]

Describe the bug

When using preact with vite, a conflict arises when multiple contexts are defined using the same variable name. Even if these contexts are created in separate files, if they are assigned to the same variable name, they seem to override each other. This only happens when running npm run dev, not when running npm run build or npm run preview.

To Reproduce

I created a minimal example exhibiting this behavior: https://github.com/rjvdw/preact-context-bug. Foo.jsx, Bar.jsx and Baz.jsx all define their own context. Foo.jsx and Bar.jsx use const ctx = createContext, whereas Baz.jsx uses const ctxBaz = createContext.

Expected behavior

When running this app, you are presented with three buttons. I would expect each button to only increment the counter directly next to this button, but instead the counters for Foo.jsx and Bar.jsx are linked. I.e. when I increment Foo, Bar is also incremented and vice versa. The counter for Baz is working as intended.

[marvinhagemeister]

I took a look into this and it seems to be caused by Prefresh our HMR implementation. When enabled two of the three signals share the exact same reference.

When Prefresh is disabled it works as expected.

It can be disabled by changing the vite config to this:

export default defineConfig({
  plugins: [preact({ prefreshEnabled: false })],
});

I wonder if something isn't properly unsubscribed or something.

[rschristian]

Might be related to #488?

In the linked issue there's an additional bug report of the fileHash being borked when the consumer uses the same default value and variableDeclaration for the createContext

[JoviDeCroock]

This should be resolved by #524