Lazy loading fontawesome icons in vue3 + vite not working in DEV - vuejs3

Question

In my vue3+vite project I'm using the official fontawesome vue3 package (see use with vue).
In order to enable tree-shaking you need to statically load the necessary icons (or possibly all of them) in advance using library.add. See for instance the following App.vue
<script setup>
import { ref, computed } from "vue";
import { library } from "#fortawesome/fontawesome-svg-core";
import { FontAwesomeIcon } from "#fortawesome/vue-fontawesome";
import { definition } from "#fortawesome/free-solid-svg-icons/faTruck";
library.add(definition);
const icon = ref("");
const showIcon = () => { icon.value = `fa-solid fa-truck`; };
</script>
<template>
<button #click="showIcon">Show Truck Icon</button>
<div v-if="icon">
<font-awesome-icon :icon="icon" />
</div>
</template>
here we statically load the truck icon and when you click the button the icon shows up.
What I was trying to do is loading the icons on demand (in this case, only when the button is clicked), using the following code:
<script setup>
import { ref, computed } from "vue";
import { library } from "#fortawesome/fontawesome-svg-core";
import { FontAwesomeIcon } from "#fortawesome/vue-fontawesome";
const modules = import.meta.glob(
"../node_modules/#fortawesome/free-solid-svg-icons/faTruck.js",
{ eager: false, import: "definition" }
);
const icon = ref("");
const showIcon = () => {
Object.values(modules)[0]().then((elem) => {
library.add(elem);
icon.value = `fa-solid fa-truck`;
});
};
</script>
<template>
<button #click="showIcon">Show Truck Icon</button>
<div v-if="icon">
<font-awesome-icon :icon="icon" />
</div>
</template>
But this doesn't work in "develpment" (npm run dev):
it makes a call to http://localhost:5173/node_modules/#fortawesome/free-solid-svg-icons/faTruck.js
then raises an error: Uncaught (in promise) ReferenceError: exports is not defined
while it works fine when the bundle is built (npm run build then for example serve the dist folder with http-server)
I suspect the problem is related to the fact that in development mode faTruck.js module is used "as is", while it is transpiled in the build phase.
Is there a solution?
NOTE:
The example contains only the "truck" because is over-simplified, but actually any icon should be loaded; i.e. the actual path in import.meta.glob should be ../node_modules/#fortawesome/free-solid-svg-icons/fa*.js
Full steps to reproduce the issue:
npm create vue#3 # accepts all defaults
cd vue-project
npm i #fortawesome/fontawesome-svg-core #fortawesome/free-solid-svg-icons #fortawesome/vue-fontawesome
# replace src/App.vue with the one indicated above
# run in dev with
npm run dev
# or build for prod and then expose using http-server
npm run build
npx http-server dist

Answer 1

Explaination
According to the Vite pre-bundling docs:
Vite's dev serves all code as native ESM. Therefore, Vite must convert dependencies that are shipped as CommonJS or UMD into ESM first
But when you use glob import with dynamic variables, your modules will not be pre-bundled. Since #fortawesome/free-solid-svg-icons/faTruck.js is a CommonJS file, it can not be used directly in ESM. And you are right that Vite does transform the module on production build, so it works well on production.
You may think about the optimizeDeps.include option but unfortunately, it does not help in this situation. Even if you add your module to the include list, Vite does pre-bundle your module but it will not use that pre-bundled file for your dynamic import. It still uses the file in node_modules/#fortawesome/free-solid-svg-icons/ folder.
I'm afraid that there is no straightforward solution to your problem. See this issue
Workaround
Just make it work differently on dev and prod.
const showIcon = async () => {
let x = 'faTruck'
let definition
if (import.meta.env.PROD) {
const iconModule = await import(
`../node_modules/#fortawesome/free-solid-svg-icons/${x}.js`
)
definition = iconModule.definition
} else {
const iconModule = await import(`#fortawesome/free-solid-svg-icons`)
definition = iconModule[x]
}
library.add(definition)
icon.value = `fa-solid fa-truck`
}
With this code, you still have the benefit of lazy loading on production and a smooth dev server to work
Another approach
Hard-coding your import list like so:
const showIcon = async (iconName) => {
const listImport = {
faTruck: () => import(`#fortawesome/free-solid-svg-icons/faTruck`),
faWarning: () => import(`#fortawesome/free-solid-svg-icons/faWarning`),
}
const iconModule = await listImport[iconName]()
console.log('iconModule', iconModule)
library.add(iconModule.definition)
}
But I bet you have hundreds of icons in your list so it hardly is an option