Resize observer contentBoxSize binding is undefined

[DanielKerrigan]

Describe the bug

I am trying to use the new resize observer bindings that were released in 3.59.0. bind:borderBoxSize is working as expected, but I have not been able to get bind:contentBoxSize to work. Its value stays undefined. I've tested in Safari, Chrome, and Firefox on macOS.

I'm not familiar with the Svelte codebase, but I wonder if the issue might be in these lines:

{
	event_names: ['elementresizecontentbox'],
	filter: (_node: Element, name: string) =>
		regex_content_rect.test(name) ?? regex_content_box_size.test(name)
},

I think the check should be regex_content_rect.test(name) || regex_content_box_size.test(name). The regex test() method returns either true or false. The righthand side of ?? is only evaluated if the lefthand side is null or undefined, which can't happen here. I would be happy to submit a PR if this is the fix.

Reproduction

REPL demo showing that bind:borderBoxSize works, but bind:contentBoxSize does not.

Logs

No response

System Info

System:
    OS: macOS 13.2.1
    CPU: (8) arm64 Apple M1
    Memory: 53.31 MB / 16.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 18.9.0 - ~/.nvm/versions/node/v18.9.0/bin/node
    Yarn: 3.5.1 - ~/.nvm/versions/node/v18.9.0/bin/yarn
    npm: 8.19.1 - ~/.nvm/versions/node/v18.9.0/bin/npm
  Browsers:
    Chrome: 113.0.5672.92
    Firefox: 112.0.2
    Safari: 16.3
  npmPackages:
    svelte: ^3.59.0 => 3.59.1

Severity

annoyance

[samal-rasmussen]

Still broken in 4.2.9:

https://svelte.dev/repl/1d03a63e4c1e48d89e5c6404fa6b9bea?version=4.2.9

But fixed in Svelte 5:

https://svelte-5-preview.vercel.app/#H4sIAAAAAAAAE41TTU_DIBj-K9iYTJN2H4kxhtYaPenZg4dth7W8a8kYkEJnZ9P_Lm23daBZdoOHl-eLUHtrykB5eF57fLUFD3uvUnq-p_ey3agdMA1mr0RZpC0SqbSgUscLvtAMNEpEQaB4E9Un_YHwiKaCa-D6DDYHt3iY_qJE5-jZvo5e7P18uhxTziiH7hSjYBa6RO9As1xfw5QwkW4sop5q8Ho0Zbs3XDZwwdYwePJ1BdkFZ0owGDOR3Y36PCZWhZQZHflOmb7byX34H81B_ZzHKcD_k6JliibDw_OI0B1KKCfYbr2D7HxxNDHD_a2bIEAfCCoJqUY6pwppgRJAs-kUVehxioLADEYydrKaFms7bGPmaydvE01kfEHlqRV5GETcJloVp4pOxm3joGM4lN4z6H5C20fdLhZargihPMMmlazCHvtuybBxcELyjgobPycoWaWbrBAlJ0EqmCgwUhqAJazs_1XTPUInaT7kVhC6pkA8rIsSmmXzC35a4HvLAwAA

[Rich-Harris]

Closing since this is fixed in Svelte 5