Canonical: Generate a stable cache key in redirect_guess_404_permalink()

[maheshbohara]

[64043] added object caching to the database lookup in redirect_guess_404_permalink(). The cache key is md5( $query ), but for the default (loose) guess the query contains a LIKE clause built by $wpdb->prepare(), so the literal % has been swapped for the wpdb::placeholder_escape() token.

That token is regenerated on every request, so the cache key is different on every request. With a persistent object cache the stored value is never read back: each 404 guess is a cache miss followed by a new cache write.

This PR removes the placeholder escape before hashing, which is what WP_Query::generate_cache_key(), WP_Term_Query and WP_User_Query already do.

Testing

Before the change, running the same lookup in separate PHP processes stores a different key each time:

wp eval 'global $wp_object_cache; set_query_var( "name", "hello" ); redirect_guess_404_permalink(); $p = new ReflectionProperty( $wp_object_cache, "cache" ); foreach ( array_keys( $p->getValue( $wp_object_cache )["post-queries"] ) as $k ) { echo "$k\n"; }'

After the change the key is the same on every run.

A unit test is included. It captures the SQL through the query filter (where the placeholder escape has already been removed) and asserts that the result is cached under the key derived from that SQL. It fails on trunk and passes with this change. The existing tests from [64043] could not catch this because they call the function twice in one PHP process, where the token is constant.

npm run test:php -- --filter redirect_guess_404_permalink tests/phpunit/tests/canonical.php

Trac ticket: https://core.trac.wordpress.org/ticket/66282

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus
Used for: Investigating and reproducing the bug, and drafting the patch, unit test and this description. I reviewed the changes and ran the tests locally.

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[peterwilsoncc]

Thank you!

This change looks good to me. I took the liberty of pushing 035f12b to be a little more precise with the test.

I split the final assertion you wrote in to two:

1. Check the cache key is generated using the SQL query
2. Check the cache key does not include the placeholder

I'll aim to commit this on Monday Australian time, let me know if you're not happy with the changes.

[maheshbohara]

Thanks for the review and the test tweak, @peterwilsoncc. I'm happy with the changes. The one failing check (Upgrade from 7.1 / PHP 8.4 / MySQL 8.4) looks like a runner issue: WP-CLI failed to install, so wp wasn't found.