Swiffy runtime causes issues with Vue's internals

[alexthunder3]

Hello.
We've built an ionic app with Vue3, which has been super fun so far. Problem is, we need to load an old script in order to show some animations. The script is swiffy, it's a tool that google developed and retired back in 2016 that converted flash animations.
The app does seem to work, animations are visible, but vue starts spamming with warning about every single prop on every component in the page where it's included (including all parent components), and the warnings continue to spam the console.log across the pages. So visiting the page where the script is included causes some kind of "permanent" damage to Vue's internals, and I've no clue where to look.

The warnings look like this:
[Vue warn]: Invalid prop: type check failed for prop "size". Expected , got String with value "default".
where the "default" value is coming from the components passing their correct props, but Expected is apparently nothing. So sounds like Vue "forgets" what props it's supposed to expect.

We include swiffy with a simple component that loads the js script, like so:

<template>
    <component :is="'script'" src="script/swiffy/swiffy_v7.4.1_runtime.js" />
</template>

Swiffy has to be loaded before the html, so in the page we set a ref to true when :onload resolves, which we use as a condition for rendering the html. Swiffy runtime can be seen here: https://www.gstatic.com/swiffy/v7.4.1/runtime.js

Does anyone have an idea what I can look for?
I've tried asking copilot to look into the script to find something that would conflict with Vue's internals, but of course it couldn't find anything. We have other scripts included as well, but only swiffy causes these issues.
I've tried poking around in Vue's internals, but I'm new to Vue/javascript, so I'm not really sure where to look. The swiffy runtime does do a lot, and touches all sorts of global things and uses Object.defineProperty abundantly, which according to copilot is a possible conflict, but that's as far as I got.

Is this even a real problem? The app seems to work, but does get slow with time (likely due to massive console.log spam), but as far as I can see from the Vue runtime-core, these warnings don't get logged in NODE_ENV=production.

Any pointers/advice is much appreciated 🙏

[LinusBorg]

I poked around a bit in the minified source of swiffy. It seems that it overrrides the toString() method of all global constructors like String.prototype.toString, and I assume this method now returns something that breaks our getTypeimplementation here:

core/packages/runtime-core/src/componentProps.ts

Line 600 in 9ea2b86

const match = ctor && ctor.toString().match(/^\s*(function|class) (\w+)/)

What does this mean for you?

1. This is not breaking your app. prop validation warning are meant as a hint during development and are removed in production. So your app will work fine.
2. You likely won't be able to get rid of these warnings in production without patching either swiffy or vue.

We will not adjust Vue's code to accommodate for whatever swiffy breaks here.

[alexthunder3]

Thank you very much 🙏