A current_page_parent CSS class is not added to relevant WP menu items if the query is for a custom post type single item

[henry.wright]

A current_page_parent CSS class doesn't get added to relevant post type archive menu items if the current query is for a custom post type single item.

[henry.wright]

Steps to reproduce

1. Add a post type archive item to a WP menu
2. Visit a single item of that post type

Note that the current_page_parent CSS class isn't added to the menu item.

[henry.wright]

Please find 38836.diff attached.

[welcher]

Patch looks ok to me. Let's get some unit test in place for it.

[christophherr]

38836.2.diff adds unit tests.

[desrosj]

The latest patch needs a refresh to apply cleanly.

[diouldebalde]

<?php
[[Image([''''])]]

[donmhico]

Refreshed the patch. I've re-test the patch and re-run the unit tests as well. Everything looks good.

[davidbaumwald]

@SergeyBiryukov The patch looks good and clean. Is this something we can include for 5.3 Beta 1 today? If not, feel free to update the milestone to whatever you think is realistic.

[davidbaumwald]

With version 5.3 Beta 1 releasing shortly, the deadline for enhancements is now passed. This is being moved to Future Release.

## Summary

When viewing a singular post of a public, non–built-in custom post type, the corresponding post type archive nav menu item did not receive the current_page_parent class, unlike the behavior users expect for “section” parents in menus.

This change:

• Precomputes public custom post types once in _wp_menu_item_classes_by_context().
• On singular views of those types, adds current_page_parent to matching post_type_archive menu items (same post type in object).

Refreshes the approach from older patches on the ticket and adds PHPUnit coverage.

## Testing

phpunit (filtered): Tests_Post_Nav_Menu — all tests passed locally.

Trac ticket: https://core.trac.wordpress.org/ticket/38836

## Use of AI Tools

AI assistance: Yes
Tool(s): Cursor (AI-assisted editor)
Used for: Guidance on contribution workflow, patch review, test structure, and PR text; implementation was applied in the local checkout, run through PHPUnit (Tests_Post_Nav_Menu), and reviewed by me before opening this PR.