Post Date: Migrate to textAlign block support

[huzaifaalmesbah]

What?

Part of #60763

Migrates the Post Date block to use the textAlign block support instead of a custom textAlign attribute. As a consequence, it also enables global styles support for textAlign on the Post Date block.

Why?

The Post Date block currently implements its own text alignment logic with a custom textAlign attribute and a manual AlignmentControl in the toolbar, duplicating code that should be handled by the centralized textAlign block support.

This migration reduces code duplication and consolidates alignment handling across blocks.

How?

Replaces the custom logic with the block supports, adds deprecation and fixes transforms.

Testing Instructions

1. Create a new Post Date block and test text alignment (left, center, right).
2. Verify alignment works correctly in both the editor and the frontend.
3. Open a post with existing Post Date blocks that have alignment set.
4. Verify they migrate correctly (no console errors, no visual changes).
5. Confirm the block is valid after migration by checking there are no block validation warnings in the console.

[github-actions]

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Co-authored-by: huzaifaalmesbah <[email protected]>
Co-authored-by: t-hamano <[email protected]>

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[t-hamano]

{ ( blockEditingMode === 'default' || ! isDescendentOfQueryLoop ) &&
	activeBlockVariationName !== 'post-date-modified' &&
	( ! isDescendentOfQueryLoop || ! activeBlockVariationName ) && (
		<BlockControls group="block">
			<ToolbarGroup>
			</ToolbarGroup>
		</BlockControls>
	) }

All of the conditional checks here should be able to be consolidated.

[t-hamano]

This doesn't seem to be the expected result. The text alignment seems to be discarded.

[huzaifaalmesbah]

The v2 deprecation migration was unintentionally overwriting v4's correctly migrated textAlign attribute back to the top level, because both were triggering sequentially on the original block attributes.

I fixed this by updating v2's isEligible check to explicitly exclude blocks that have textAlign, allowing v4 to handle them correctly. The fixtures have been regenerated with the proper output!

[t-hamano]

I fixed this by updating v2's isEligible check to explicitly exclude blocks that have textAlign

The v2 deprecation is a necessary step to migrate block attributes to Block Bindings. Adding exclusion rules will cause unintended problems. Please try the following:

1. Open the code editor and insert the following HTML:

<!-- wp:post-date {"displayType":"modified"} /-->
<!-- wp:post-date {"displayType":"modified", "textAlign":"right"} /-->

2. Back to the Visual editor, and back to the Code editor again.
3. Unintended migration is occurring in a block that has textAlign.

✅

<!-- wp:post-date {"metadata":{"bindings":{"datetime":{"source":"core/post-data","args":{"field":"modified"}}}},"className":"wp-block-post-date__modified-date"} /-->

❌

<!-- wp:post-date {"datetime":"2026-03-16T10:14:11.214Z","style":{"typography":{"textAlign":"right"}}} /-->

[t-hamano]

The solution is probably to add migrate: migrateTextAlign to v1, v2, and v3 as well. See #74383 (comment)

[t-hamano]

LGTM 👍