[examples/mentions] Pasting or cutting a selected mention node crashes locally

[wudidewo12]

Description

In the Mentions example, copying and pasting a selected mention node, or cutting a selected mention node, crashes the local page. The live Slate example handles the same selected mention node normally.

I reproduced this with both @R2-D2 and @Mace Windu, so this appears to affect selected mention inline void nodes generally.

Recording

Screenshots attached below:

Local actual behavior:

Live reference expected behavior:

Video attached below:

Not required unless the screenshots are not clear enough.

Sandbox

No standalone sandbox. Reproduced in the Slate examples site.

Local reproduction URL:

http://localhost:3100/examples/mentions

Reference URL:

https://www.slatejs.org/examples/mentions

Steps

To reproduce the copy/paste crash:

1. Go to http://localhost:3100/examples/mentions.
2. Click an existing mention node, such as @R2-D2 or @Mace Windu, so that the mention is selected.
3. Press Cmd+C.
4. Move the caret to another position in the editor.
5. Press Cmd+V.

Alternative cut path:

1. Go to http://localhost:3100/examples/mentions.
2. Click an existing mention node, such as @R2-D2 or @Mace Windu, so that the mention is selected.
3. Press Cmd+X.

Expectation

The selected mention node should copy/paste or cut successfully, matching the live Mentions example.

• Cmd+C then Cmd+V should insert another copy of the selected mention node.
• Cmd+X should remove the selected mention node from its original position.
• The page should not crash.

Actual behavior

On the local Mentions example, copying then pasting a selected mention node crashes the page with a runtime error. Cutting the selected mention node also crashes.

Observed error:

Cannot read properties of null (reading 'setAttribute')

Environment

• Local branch/commit: v2, ce2bd6c6
• Local URL: http://localhost:3100/examples/mentions
• Reference URL: https://www.slatejs.org/examples/mentions
• Browser: Chrome on macOS

Impact

This breaks clipboard operations for mention inline void nodes and can crash the examples page during a normal editor copy/paste or cut workflow.

[zbeyens]

🟢 95-100% confidence

Phase	🧪 Tests	🌐 Browser
Reproduced	✅ Issue screenshots/transcript show selected mention copy/paste and cut crash	✅ examples/mentions flow identified
Verified	🟢 Selected mention copy/paste and cut rows are green on current v2 07d79634	✅ No runtime crash in Chromium proof

🌐 Browser Check

• Open http://localhost:3100/examples/mentions.
• Select @R2-D2 or @Mace Windu.
• Press Cmd+C, move the caret, then press Cmd+V.
• Select a mention again and press Cmd+X.
• Confirm paste inserts another mention and cut removes the selected mention without crashing.

✅ Outcome

• Copy/paste of a selected mention no longer crashes.
• Cutting a selected mention no longer crashes.

🏗️ Design

• Chosen owner: inline void clipboard serialization.
• Why not quick patch: current runtime proof already covers the selected mention copy/paste and cut paths.
• Why not broader change: the issue is limited to selected mention inline void clipboard behavior.

🧪 Verified

• cd /Users/zbeyens/git/slate-v2 && PLAYWRIGHT_RETRIES=0 PLAYWRIGHT_BASE_URL=http://localhost:3100 bun playwright playwright/integration/examples/plaintext.test.ts playwright/integration/examples/mentions.test.ts playwright/integration/examples/paste-html.test.ts playwright/integration/examples/iframe.test.ts --project=chromium --grep "keyboard undo restores caret after middle-line typing|keyboard undo restores partial selected text replacement|keyboard undo restores select-all replacement content|copies and pastes a selected mention without crashing|cuts a selected mention without crashing|pastes copied rendered Slate content as an internal fragment before HTML import|applies parent toolbar formatting to selected iframe text"
• cd /Users/zbeyens/git/slate-v2 && bun check