Add event to alter delete website confirmation

plugins/SitesManager/API.php

@@ -394,6 +394,24 @@ public function getSitesWithAdminAccess($fetchAliasUrls = false, $pattern = fals
         return $sites;
     }
 
+    /**
+     * Returns the messages to warn users on site deletion.
+     *
+     * @param int $idSite
+     * @return array messages to warn users
+     * @throws Exception if the website ID doesn't exist or the user doesn't have super user access to it
+     * @internal
+     * @unsanitized
+     */
+    public function getMessagesToWarnOnSiteRemoval(int $idSite): array
+    {
+        $messages = [];
+        Piwik::checkUserHasSuperUserAccess($idSite);
+        Piwik::postEvent('SitesManager.getMessagesToWarnOnSiteRemoval', [$idSite, &$messages]);
+
+        return $messages;
+    }
+
     /**
      * Returns the list of websites with the 'view' access for the current user.
      * For the superUser it doesn't return any result because the superUser has admin access on all the websites (use getSitesWithAtLeastViewAccess() instead).

plugins/SitesManager/tests/Integration/ApiTest.php

@@ -714,6 +714,25 @@ public function testGetSitesWithAdminAccessShouldApplyPatternAndLimit()
         $this->assertReturnedSitesContainsSiteIds([5, 15], $sites);
     }
 
+    public function testGetMessagesToWarnOnSiteRemovalShouldReturnDefaultValue()
+    {
+        $pluginManager = Plugin\Manager::getInstance();
+        if ($pluginManager->isPluginActivated('TagManager')) {
+            $pluginManager->deactivatePlugin('TagManager');
+        }
+        API::getInstance()->addSite("site1", ["http://piwik.net", "http://piwik.com"]);
+        API::getInstance()->addSite("site2", ["http://piwik.com", "http://piwik.net"]);
+        $this->assertEmpty(API::getInstance()->getMessagesToWarnOnSiteRemoval(1));
+        $this->assertEmpty(API::getInstance()->getMessagesToWarnOnSiteRemoval(2));
+    }
+
+    public function testGetMessagesToWarnOnSiteRemovalShouldThrowExceptionIfNotSuperUser()
+    {
+        $this->expectException(\Exception::class);
+        $this->createManySitesWithAdminAccess(1);
+        API::getInstance()->getMessagesToWarnOnSiteRemoval(1);
+    }
+
     private function createManySitesWithAdminAccess($numSites)
     {
         for ($i = 1; $i <= $numSites; $i++) {