Vite dev server bundles two versions of a file causing `svelte-routing` to break

Describe the bug

Using svelte-routing as the router, when navigate() is called, the address bar url changes, but the displayed route component doesn’t change. It appears that triggering of some event listeners are not working when running with Vite. (https://github.com/EmilTholin/svelte-routing/issues/199#issuecomment-826684338)

The same code works when used with plain Rollup, and when used with vite build + vite preview. Only vite dev server has the issue.

This could be related to https://github.com/vitejs/vite/issues/443.

Reproduction

https://codesandbox.io/s/distracted-star-uhss6?file=/src/App.svelte

System Info

Output of npx envinfo --system --npmPackages vite,@vitejs/plugin-vue --binaries --browsers: I don’t think this matters because I have tested the repro locally in different machines and inside codesandbox.io. Happy to provide if needed.

Used package manager: yarn

Logs

Not available. No errors are shown in the browser console either.

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[itsfarseen]

Okay it’s not being reloaded. Vite bundles two versions of history.js to the browser. The versions received by App.svelte and Router.svelte are different, so the listener variable changed by navigate() call in App.svelte is different from the one Router.svelte gets.

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Details:

Path to Version 1: Goes to Which goes to

Version 1 of history.js shown in red.

Version 2 is loaded by Router.svelte Which goes to

[itsfarseen]

@sidharthramesh I don’t think svelte routing is doing anything wrong here.
It’s an edge case that happens due to the way Vite dev server optimizes things.
We can easily opt out of that from the configuration. It doesn’t affect dev server performance much. It also doesn’t happen with the final build.