Features: Preload the options experiments read on every request

[ekamran]

What?

Follow up to #1113. See #1112.

Loads the two options that experiments read on every request together with the feature toggles, so all of them come from one query instead of three.

Why?

#1113 loads the 21 feature toggles with one query. Two more options were still looked up one by one on every request: wpai_markdown_feeds_flush_rewrite (Markdown Feeds reads it on wp_loaded) and wpai_key_encryption_resume_migration (Key Encryption reads it on init). Both are flags that are deleted after use, so they are missing most of the time, and a missing option costs a query on every request on sites without a persistent object cache. Asked for as a new PR in #1113.

How?

• Abstract_Feature::get_preloaded_options() is new. It returns the names of options a feature reads on every request, empty by default.
• Markdown_Feeds and Key_Encryption return their flag from it.
• The Loader adds those names to the toggle names and passes everything to wp_prime_option_caches() in the same call. A later get_option() of a flag is served from the cache, whether the row exists or not, so the flags are consumed exactly as before.
• The persistent object cache check from Features: Load all feature toggles with one query #1113 is unchanged, nothing is primed there.
• Third-party features get the same by defining get_preloaded_options(). Features that do not define it are skipped, the same optional-method pattern Settings_Registration uses for register_settings().

Queries per request on a fresh install with nothing switched on (MariaDB 12.3.3, WordPress 7.1.2, no persistent object cache, develop already has #1113):

Request	develop	This PR
Home page	27	25
Single post	31	29
REST index (/?rest_route=/)	11	9
Feed	18	16
wp-login.php	10	8
admin-ajax.php	11	9
wp-cron.php	7	5

Same 2 fewer queries on SQLite with WordPress 7.1. Against 1.4.0 the home page goes from 47 to 25 queries.

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code and Codex
Used for: Implementation, tests, measurements, and PR wording. I reviewed the reasoning and test results, and I take responsibility for the contribution.

Testing Instructions

1. Use a site without a persistent object cache with the plugin active. Save the snippet from Features: every never-enabled feature costs one database query on every request #1112 as wp-content/mu-plugins/count-ai-option-queries.php.
2. Load any page. On develop the log line shows 2 single lookups for wpai_ options. With this PR it shows 0.
3. Enable Markdown Feeds under Settings > AI, load any page, then open /feed/markdown/. It shows the feed, so the flush flag was still read and consumed. Switch it off and the feed is a 404 again.

Automated:

• npm run test:php -- --filter 'test_preloaded_options|test_get_preloaded_options_defaults_to_empty' runs the four new tests. All four fail on develop (three undefined method errors, one query count) and pass here.
• The full PHP suite passes on single site and on multisite (1772 tests).
• composer lint and PHPStan pass.

Changelog Entry

Fixed - The Markdown Feeds and Key Encryption flags are loaded together with the feature toggles instead of with one query each on every request.

[github-actions]

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Co-authored-by: ekamran <ekamran@git.wordpress.org>
Co-authored-by: dkotter <dkotter@git.wordpress.org>

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[codecov]

Codecov Report

❌ Patch coverage is 92.30769% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.62%. Comparing base (da50fbb) to head (0096c06).
⚠️ Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
includes/Features/Loader.php	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #1119   +/-   ##
==========================================
  Coverage      81.61%   81.62%           
- Complexity      3083     3088    +5     
==========================================
  Files            129      129           
  Lines          12289    12297    +8     
==========================================
+ Hits           10030    10037    +7     
- Misses          2259     2260    +1     

Flag	Coverage Δ
unit	81.62% <92.30%> (+<0.01%)	⬆️

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[ekamran]

Thanks for the fixes. Noted for the next ones: @since x.x.x placeholders and list<string>.