Formatting: Prevent wpautop() from splitting anchors around block elements

[ArkaPrabhaChowdhury]

Prevents wpautop() from generating invalid markup when an anchor wraps one or more block-level elements. The affected anchors are temporarily treated as block containers during paragraph cleanup, then restored without changing normal inline anchors. The placeholder name is selected to avoid collisions with existing content.

Trac ticket: https://core.trac.wordpress.org/ticket/40202

Testing

• npm run test:php -- --group 40202
• npm run test:php -- --filter Tests_Formatting_wpAutop
• PHPCBF on the changed files
• PHPCS on the changed files

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Used for: Ticket analysis, implementation, test coverage, validation, and pull request drafting; the final changes were reviewed and validated by the contributor.

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[github-actions]

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[wpankit]

Picked through the diff. Looks like this only touches formatting.php, but wpautop also has a JS version in @wordpress/autop that usually needs the same fix to stay in sync.

The other thing on wpautop is regressions. Do the existing Tests_Formatting_wpAutop cases still pass, or just the new ones? Happy to run it if you haven't.

[ArkaPrabhaChowdhury]

Thanks @wpankit — you are right about keeping the JavaScript implementation synchronized.

The @wordpress/autop source is maintained in Gutenberg (the wordpress-develop dist files are ignored generated output), so I added the matching implementation and regression coverage in WordPress/gutenberg#80232: WordPress/gutenberg#80232

Validation completed:

• Full PHP Tests_Formatting_wpAutop class: 26 tests, 36 assertions passed.
• Targeted PHP ticket group: 1 test, 2 assertions passed.
• Full JavaScript packages/autop/src/test/index.test.ts: 19/19 tests passed.
• JavaScript ESLint and the packages/autop TypeScript check passed.

So both the existing PHP and JavaScript regression suites pass, not only the new cases.

[github-actions]

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Props arkaprabhachowdhury, ankitmaru.

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