MAGETWO-99418: Deliver critical PR for 2.3.2

Author: vzabaznov

app/code/Magento/MessageQueue/Model/PoisonPillCompare.php

@@ -35,6 +35,6 @@ public function __construct(
      */
     public function isLatestVersion(string $poisonPillVersion): bool
     {
-        return (string) $poisonPillVersion === (string) $this->poisonPillRead->getLatestVersion();
+        return $poisonPillVersion === $this->poisonPillRead->getLatestVersion();
     }
 }

app/code/Magento/MessageQueue/Model/ResourceModel/PoisonPill.php

@@ -50,17 +50,17 @@ public function put(): string
     /**
      * @inheritdoc
      */
-    public function getLatestVersion(): ?string
+    public function getLatestVersion(): string
     {
         return $this->getVersionFromDb();
     }
 
     /**
      * Returns version form DB or null.
      *
-     * @return string|null
+     * @return string
      */
-    private function getVersionFromDb(): ?string
+    private function getVersionFromDb(): string
     {
         $select = $this->getConnection()->select()->from(
             $this->getTable(self::QUEUE_POISON_PILL_TABLE),
@@ -69,6 +69,6 @@ private function getVersionFromDb(): ?string
 
         $result = $this->getConnection()->fetchOne($select);
 
-        return $result === false ? null : $result;
+        return (string)$result;
     }
 }

lib/internal/Magento/Framework/MessageQueue/PoisonPill/PoisonPillRead.php

@@ -19,8 +19,8 @@ class PoisonPillRead implements PoisonPillReadInterface
      *
      * @return string
      */
-    public function getLatestVersion(): ?string
+    public function getLatestVersion(): string
     {
-        return null;
+        return '';
     }
 }

lib/internal/Magento/Framework/MessageQueue/PoisonPill/PoisonPillReadInterface.php

@@ -17,5 +17,5 @@ interface PoisonPillReadInterface
      *
      * @return string
      */
-    public function getLatestVersion(): ?string;
+    public function getLatestVersion(): string;
 }