[Sourav61]

Description

Fixes https://core.trac.wordpress.org/ticket/66379.

Switching from Text to Visual mode in the Classic Editor with the cursor positioned immediately after a closing </li> tag causes TinyMCE to restructure the list unexpectedly.

This happens because the editor inserts a temporary selection bookmark directly inside the list, creating an invalid HTML structure. TinyMCE then normalizes the markup by nesting preceding list items inside an additional <li style="list-style-type: none;"> element, resulting in unwanted indentation and changes to the original list.

Changes

• Adjusted both selection endpoints to ensure bookmarks positioned after </li> tags or their trailing whitespace are inserted inside the preceding list item.
• Prevented TinyMCE from receiving invalid list structures during editor switching.
• Preserved the original list markup and cursor selection when switching between Text and Visual modes.

Testing

• Added regression tests covering ordered, unordered, and nested lists, whitespace variations, uppercase tags, list item attributes, and selection ranges.
• Confirmed all 41 assertions pass with the fix, while 27 assertions fail with the original implementation.
• Verified the behavior with WordPress's TinyMCE plugin and wpautop enabled.
• Confirmed JavaScript lint checks pass.

Use of AI Tools

AI assistance: Yes
Tool(s): ChatGPT
Model(s): GPT-6
Used for: Assistance with investigation and implementation suggestions. Final implementation and regression tests were reviewed and verified manually.

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