support `document` containers in cleanup

[quisido]

What:

When container is set to document, the cleanup step fails:

TypeError: Cannot read properties of null (reading 'removeChild')

This is because the code assumes document.body exists:

    if (container.parentNode === document.body) {
      document.body.removeChild(container);
    }

In reality, both container.parentNode and document.body are null.

Why:

The tests erroneously fail.

How:

The attempt to remove the container from the body now only occurs when the body exists.

Checklist:

• [ ] Documentation added to the docs site N/A
• [ ] Tests
• [ ] TypeScript definitions updated N/A
• [x] Ready to be merged

resolves #1329

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[eps1lon]

Please add a test.

I don't understand why document.body would be null? Isn't that always defined?

[quisido]

I don't know the setup, but is null when container is document. Locally, I fixed this by setting it to document.createElement('body').

I unfortunately do not have bandwidth to write a test for this, but the reproduction steps should be simple enough.

I ran into this specifically when writing a test for a NextJS root layout, which attempts to mount an HTML and body element. The docs say to use container: document when rendering your own HTML element, which fixed the previous error during test but introduced the OP error during cleanup.

[MatanBobi]

@quisido thanks for taking the time to add this but we are not merging changes without proper coverage for them.

[quisido]

@quisido thanks for taking the time to add this but we are not merging changes without proper coverage for them.

Understandable. The PR is welcome to be updated. I opened an issue for it for tracking as well. I can try updating tests as time permits, but I wanted the problem and solution to both be documented.