Svelte 5: TypeError while setting an attribute on a custom element in Adobe UXP

[kapooostin]

Describe the bug

Adobe UXP supports a subset of custom elements from Spectrum web components. They work fine in Svelte 4. With Svelte 5 it's impossible to use them as setting an attribute:

<sp-button variant="primary">Button</sp-button>

throws an error:

Uncaught TypeError: Cannot read properties of null (reading 'constructor')

But setting an event handler works as expected:

<sp-button onclick={()=>counter++}>Inc</sp-button>

I wrapped in the compiled script a troublesome call of

set_custom_element_data(sp_button, "variant", "primary")

into try/catch block and somehow it works if I attempt to set an attribute in a catch branch

try {
  set_custom_element_data(sp_button, "variant", "primary");
} catch(e) {
  set_custom_element_data(sp_button, "variant", "primary");
}

Reproduction

Not sure as you need Adobe Photoshop and dev environment to run and debug a plugin and the repo with the plugin to test. But I can write down the instructions on how to set up everything were anybody to bother.

Logs

/assets/index-B7eQNQ0h.js:2139 Uncaught TypeError: Cannot read properties of null (reading 'constructor')
    at get_setters (VM301 index-B7eQNQ0h.js:2139)
    at set_custom_element_data (VM301 index-B7eQNQ0h.js:2120)
    at App (VM301 index-B7eQNQ0h.js:2409)
    at VM301 index-B7eQNQ0h.js:2038
    at update_reaction (VM301 index-B7eQNQ0h.js:1033)
    at update_effect (VM301 index-B7eQNQ0h.js:1195)
    at create_effect (VM301 index-B7eQNQ0h.js:583)
    at branch (VM301 index-B7eQNQ0h.js:661)
    at VM301 index-B7eQNQ0h.js:2022
    at update_reaction (VM301 index-B7eQNQ0h.js:1033)

System Info

System:
    OS: macOS 14.6.1
    CPU: (16) x64 Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz
    Memory: 4.71 GB / 64.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.1.0 - ~/.volta/tools/image/node/22.1.0/bin/node
    Yarn: 1.22.21 - ~/.volta/tools/image/yarn/1.22.21/bin/yarn
    npm: 10.8.3 - ~/.volta/tools/image/npm/10.8.3/bin/npm
    bun: 1.1.31 - ~/.volta/bin/bun
  Browsers:
    Chrome: 129.0.6668.101
    Safari: 17.6
  npmPackages:
    svelte: ^5.0.0-next.270 => 5.0.3
  
  Adobe Photoshop 25.15.0
    UXP 7.4.

Severity

blocking an upgrade

[7nik]

It looks like the same problem as in #13691 but in another use case.

[kapooostin]

It looks like the same problem as in #13691 but in another use case.

And probably as in #13414.
I tried to check for constructor.name on Element and document.createElement(’sp-button’), but it doesn't throw.
It's ‘Function’ for Element and empty string for sp-button.