12: Conflict resolution

[nikolaystrikhar]

What: Conflict\Resolver finds a registered sub-plugin whose standalone is still active and applies its policy — defer, notify, or deactivate.

Usage:

Loader::register( [
    'slug'                       => 'give-recurring',
    'bundled_plugin_file'        => GIVE_PLUGIN_DIR . 'subs/give-recurring/give-recurring.php',
    'plugin_loaded_constant'     => 'GIVE_RECURRING_VERSION',
    'standalone_plugin_basename' => 'give-recurring/give-recurring.php',
    'conflict_policy'            => Conflict_Policy::DEACTIVATE, // the default
    'conflict_notice_message'    => static fn() => __( 'Recurring ships with Give now.', 'give' ),
] );

The standalone is deactivated, the merge notice is queued, and the admin lands back on the screen they were on with it gone.

Why this way: default: sits on the NOTICE_ONLY branch, not the DEACTIVATE one. Conflict_Policy::is_valid() normalises an unrecognised policy first, so default: is unreachable today — but it is one refactor from being live, and a fourth policy constant added without a matching case must not be read as consent to turn off a plugin the site owner deliberately activated. The two safety gates sit in different places on purpose: request-level gating (interactive admin GET only — not cron, not WP-CLI, not ajax, not a form POST) lives in the Loader trampoline where rebinding the resolver cannot drop it, because ungated this turns a visitor's checkout POST into a 302 that discards the order; the activate_plugins check lives in the resolver, because a host that binds its own resolver owns its own policy, and plugins_loaded fires long before auth_redirect() so an anonymous GET of an admin URL reaches this code. The redirect matches on the screen basename rather than a substring of admin_url(): wp_get_referer() prefers the _wp_http_referer field, which holds a bare path, so a URL comparison misses every admin form POST and the whole network admin.

Verify: slic run unit and slic run unit --env multisite — 298 tests green on both legs, plus composer test:analysis. exit is never mocked: wp_safe_redirect is stubbed to throw, and each test asserts both that it halted and the halt message, so "never redirected at all" cannot pass silently. Not covered here: the activation callback (#13) and the activation-error rewrite (#14). Rebased onto #11; the resolver interface now lives at Conflict\Contracts\Resolver_Interface per the folder-scoped convention, and the notices collaborator is merged main's Notices\Queue.