snippet-wc-subs-control-early-renewal-rules.php

<?php
/**
  * Allow third-parties to filter whether the customer can renew a subscription early.
  *
  * @since 2.3.0
  *
  * @param bool            $can_renew_early Whether early renewal is permitted.
  * @param WC_Subscription $subscription    The subscription being renewed early.
  * @param int             $user_id         The user's ID.
  * @param string          $reason          The reason why the subscription cannot be renewed early. Empty
  *                                         string if the subscription can be renewed early.
  */
function mx_override_subscription_early_renewal_rules($can_renew_early, $subscription, $user_id, $reason)
{
  // Example subscription product ID that is NOT auto-renewing (or anything else in this list:)
  // https://woocommerce.com/document/early-renewal/#section-3
  $MY_PRODUCT_ID = 12345;
  
  // What items does this subscription have?
  foreach($subscription->get_items() as $item_id => $item_data)
  {
    // This subscription contains the product I want to allow early renewal for
    if ($item_data->get_product_id() == $MY_PRODUCT_ID)
    {
      // Allow early renewal
      $can_renew_early = true;
    }
  }

  return $can_renew_early;
}
add_filter('woocommerce_subscriptions_can_user_renew_early', 'mx_override_subscription_early_renewal_rules', 10, 4);