[Bug][legacy - v4] "[Function handler] is not a spy or a call to a spy" in play

[AliceLeRaptor]

Describe the bug

When using latest Storybook version (8.2.9) and latest addon-svelte-csf version (4.1.7) I have this error displayed in the interaction tab of my stories, when making assertions on events.

[Function handler] is not a spy or a call to a spy!

This error disappears when reloading the story or navigating to it. It only shows when the story is rendered for the first time.

Steps to reproduce the behavior

1. Create a svelte library project with npm create svelte@latest myapp, then add Storybook with npx storybook@latest init
2. Create a new component and story using templates provided by this addon documentation (remove the existing Button component and story or give a different name to the new component / story)
3. In any story from the new stories.svelte file, add a simple play function with an assertion on an event :

  <Story name="Rounded" args={{rounded: true}} play={async ({ canvasElement, args }) => {
    const { getByRole } = within(canvasElement);
    await userEvent.click(getByRole('button'));
    expect(args.event_click).toHaveBeenCalled();
  }}/>

4. Run storybook with npm run storybook and go to the story you eddited. In the interaction tab you should see the error
   [Function handler] is not a spy or a call to a spy!
5. Reload the story or navigate to another one then navigate back to the story, the error should be gone and the interaction tests should pass without errors.

Expected behavior

I expect the test in the play function to run without errors. This behavior happens when reloading the story.

Screenshots and/or logs

This is what I get when I console.log args inside the play function before reloading the story :

When reloading the story and everything is working fine, the log displays a proper spy :

Environment

• OS: Ubuntu
• Node.js version: v20.14.0
• NPM version: 10.7.0
• Browser (if applicable): Firefox / Chromium
• Browser version (if applicable): 129.0.2 for Firefox, 127.0.6533.119 for Chromium