Add a check for extensibility Object.isExtensible(Element.prototype)

[andrey-ka-97-afp]

Describe the bug

In the file svelte\src\internal\client\dom\operations.js in the method init_operations there is an extension for Element. Please add the check Object.isExtensible(Element.prototype), without it an error occurs. Our code is used on different sites, on one of them there is the code Object.freeze(Element.prototype) and because of this our scripts break. We cannot influence this in any way. It would be great if the "svelte" project adds checks before Element.prototype extensions.

Reproduction

No reproduction required, description is as clear as possible

Logs

System Info

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Severity

blocking all usage of svelte

[paoloricciuti]

Adding the check will not fix this as we are extending the element protocol indeed

[Conduitry]

AFAICT, these specific assignments are just to improve performance later on - so we're not de-opting all the time by adding properties to individual elements that are outside their prototype. So long as later assignments of custom properties to existing objects doesn't also fail because of the frozen prototype, then I think this should all still work, just with reduced performance.

However, I'm not sure we want to commit to never doing functionally necessary things to different prototypes, which we would need to commit to in order to make skipping the prototype mutations actually be useful.

[trueadm]

It should be safe to do this, and we should probably do so as these exist for performance reasons to avoid de-opts at JIT time.

[andrey-ka-97-afp]

Unfortunately, this leads to situations where "svelte" breaks. If this optimization is so important, it might be worth adding an additional setting to disable it. At the moment, we see this as a real problem for using "svelte" in the future.

[andrey-ka-97-afp]

thanks for the quick solution!