Real-time collaboration: Ensure block attribute is Y.Text

[chriszarate]

What?

Real-time collaboration: Ensure block attribute from CRDT doc is a Y.Text instance before passing it to mergeRichTextUpdate.

Why?

Our assumption that an attribute is represented in the CRDT doc as a Y.Text instance was based on the incoming block name, which may have changed. For example, a block can be transformed from core/freeform to core/paragraph (both of which carry a content attribute).

When this happens, we can encounter a fatal error in mergeRichTextUpdate by assuming a primitive string is a Y.Text instance.

How?

1. Use an instanceof check.
2. Add a test case.

Testing Instructions

1. Check out this branch.
2. Add a "Classic" block.
3. Click "Convert to blocks."

[alecgeatches]

Crazy bug find, and pretty simple-looking fix. Thank you!

[github-actions]

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Co-authored-by: alecgeatches <alecgeatches@git.wordpress.org>
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[github-actions]

Flaky tests detected in d7d04d8.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/18856954927
📝 Reported issues:

• [Flaky Test] ensures List View global shortcut works properly #51533 in /test/e2e/specs/editor/various/list-view.spec.js
• [Flaky Test] should select the wrapper div for a group #71211 in /test/e2e/specs/editor/various/block-hierarchy-navigation.spec.js