Sitemaps: Don't return a 404 status for valid sitemap requests when the main query has no posts

[i-am-chitti]

Ticket

Trac ticket: https://core.trac.wordpress.org/ticket/65945

Summary

• On a site with zero published posts, /wp-sitemap.xml renders correct XML but responds with HTTP 404, so search engines discard it.
• WP::handle_404() 404s the main query when it has no posts and no exception applies. Sitemap requests aren't in that list — they were only shielded by falling through to is_home = true, which changeset 62664 (#51542, #51543) correctly removed.
• Same class of issue as #39157, fixed for feeds in 4.7.3.

Changes

1. WP::handle_404() — exempt sitemaps alongside the other machine-readable endpoints. Placed in the first branch rather than next to is_feed(), since provider routes map paged from the URL and so never reach the elseif ( ! is_paged() ) branch.
2. WP_Sitemaps::render_sitemaps() — 404 explicitly for an unregistered provider, which previously relied on handle_404() doing it.

Intentional 404s are unaffected — sitemaps disabled and empty URL lists (#61293) call set_404() directly, later in the request.

Test

New tests/phpunit/tests/wp/handle404.php (12 tests): index, provider, paged, taxonomy, user and stylesheet routes with no posts, plus guards that unknown URLs and unregistered providers still 404.

• --group sitemaps
• --group wp --group query --group feed --group canonical --group rewrite

Screenshots

NA

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 5
Used for: Root-cause investigation, tracing history, and drafting the fix and tests.

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