Rewrite: Make url_to_postid() resolve custom post type query vars in plain permalinks

[irozum]

Summary

url_to_postid() returned 0 (or the static front page ID) for custom post type URLs when plain permalinks are in use, e.g. /?findme=slug, because only p, page_id and attachment_id query args were recognised, and the front page shortcut and the "no rewrite rules" bail-out ran before anything looked at the CPT query var.

This adds a check for public post type query vars right after the p/page_id/attachment_id check, resolving the post by post_type and name.

Trac ticket: https://core.trac.wordpress.org/ticket/42148

Testing

• Added Tests_Rewrite::test_url_to_postid_with_plain_permalinks_and_custom_post_type (fails on trunk with a static front page returned, passes with the fix).
• npm run test:php -- --filter Tests_Rewrite: OK (93 tests, 280 assertions). PHPCS shows no violations; PHPStan reports no errors.

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Sonnet 5.5
Used for: Implementation, tests, and PR description.

---

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[rejaulalomkhan]

Thanks for working on this, @irozum! Moving the check ahead of the front-page shortcut covers the case from the ticket nicely. I tested it locally:

Patch Testing Report

Patch tested: #14304

Environment

• WordPress: 7.2-alpha-63166-src (trunk 3effce4 with the PR applied)
• PHP: 8.3.35
• Server: PHP CLI (PHPUnit 9.6.38, wordpress-develop Docker environment)
• Database: MySQL 9.7.2
• Browser: N/A (unit tests)
• OS: macOS 27.0.1
• Theme: N/A
• MU Plugins: None activated
• Plugins: None activated

Steps taken

1. Ran Tests_Rewrite with the PR: all pass on single site (114 tests) and multisite (116 tests).
2. Reverted src/wp-includes/rewrite.php with the PR's test kept: test_url_to_postid_with_plain_permalinks_and_custom_post_type fails.
3. With plain permalinks, registered a non-hierarchical and a hierarchical public post type and called url_to_postid( get_permalink( $id ) ):
   • non-hierarchical (?zznote=zz-note): returns the post ID ✅
   • hierarchical parent (?zzbook=zz-parent): returns the post ID ✅
   • hierarchical child (?zzbook=zz-parent/zz-child): returns 0 ❌
4. ✅ Patch is solving the problem for non-hierarchical post types and top-level posts; child posts of hierarchical post types are not resolved yet.

Expected result

• url_to_postid() returns the post ID for custom post type URLs that use plain permalinks.

Additional Notes

• For hierarchical post types the query var holds the full path, so 'name' => 'zz-parent/zz-child' matches nothing. Looking the post up with get_page_by_path( $value, OBJECT, $post_type ) when the post type is hierarchical (or passing the query var itself to WP_Query, as the front end does) should cover it; a data set for a child post would lock that in.
• AI assistance: Claude Code was used to run the tests and the URL checks; results reviewed by me.