Svelte + Vite double import error

The problem

Using npm run dev, Vite serves two copies of the same module to the client.

This does not happen when running npm run build and serving the created bundle with an http server, for example using npx http-server -p3000 -c-1 ./dist.

This repository

This repository contains an app directory with a minimal example based on the template obtained by running npm init vite@latest test-vite-svelte -- --template svelte

It also contains svelte-vite-double-import-lib which is a minimal library that can cause this behavior.

How to run

Development mode showing the weird behavior

• download this repository
• open the app directory
• run npm install
• run npm run dev
• open a browser at http://localhost:3000
• open the javascript console, you should see "module initialized" two times

Production mode working as expected

• download this repository
• open the app directory
• run npm install
• run npm run build
• run npx http-server -p3000 -c-1 ./dist
• open a browser at http://localhost:3000
• open the javascript console, you should see "module initialized" one time