full list of changes below:

- psalm set to level 3
- [WiP] phpstan set to level 6

phpstan.neon

@@ -1,5 +1,5 @@
 parameters:
-    level: 2
+    level: 3
     paths:
         - src/
         - tests/

psalm.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0"?>
 <psalm
-        errorLevel="7"
+        errorLevel="6"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="https://getpsalm.org/schema/config"
         xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"

src/Domain/AggregateRoot/EventSourcing.php

@@ -147,7 +147,7 @@ private function apply(Event $event): void
     }
 
     /**
-     * @return Event\Sourced\Entity[]
+     * @return iterable<Event\Sourced\Entity>
      */
     private function eventSourcedEntities(): iterable
     {

src/Domain/Envelope.php

@@ -16,6 +16,8 @@
 use Streak\Domain\Id\UUID;
 
 /**
+ * @template T of object
+ *
  * @author Alan Gabriel Bem <[email protected]>
  */
 interface Envelope extends ValueObject
@@ -24,14 +26,20 @@ public function uuid(): UUID;
 
     public function name(): string;
 
+    /**
+     * @return T
+     */
     public function message();
 
     /**
      * @param string $name
      *
-     * @return float|int|string|null
+     * @return null|scalar
      */
     public function get($name);
 
+    /**
+     * @return array<scalar, scalar>
+     */
     public function metadata(): array;
 }

src/Domain/Event/Envelope.php

@@ -20,7 +20,8 @@
 /**
  * @author Alan Gabriel Bem <[email protected]>
  *
- * @template T of Event
+ * @template TMessage as Event
+ * @implements Domain\Envelope<TMessage>
  *
  * @see \Streak\Domain\Event\EnvelopeTest
  */
@@ -33,26 +34,44 @@ final class Envelope implements Domain\Envelope
     public const METADATA_PRODUCER_ID = 'producer_id';
     public const METADATA_ENTITY_TYPE = 'entity_type';
     public const METADATA_ENTITY_ID = 'entity_id';
-    private array $metadata = [];
 
     /**
-     * @param T $message
+     * @var-phpstan non-empty-array<non-empty-string, scalar>
+     * @var-psalm non-empty-array<non-empty-string, scalar>&array{
+     *          uuid: non-empty-string,
+     *          name: non-empty-string,
+     *          producer_type: non-empty-string,
+     *          producer_id: non-empty-string,
+     *          entity_type: non-empty-string,
+     *          entity_id: non-empty-string,
+     *          version?: positive-int,
+     * }
+     */
+    private array $metadata;
+
+    /**
+     * @param TMessage $message
      */
     public function __construct(UUID $uuid, string $name, private Event $message, Domain\Id $producerId, Domain\Id $entityId, ?int $version = null)
     {
-        $this->metadata[self::METADATA_UUID] = $uuid->toString();
-        $this->metadata[self::METADATA_NAME] = $name;
-        $this->metadata[self::METADATA_PRODUCER_TYPE] = $producerId::class;
-        $this->metadata[self::METADATA_PRODUCER_ID] = $producerId->toString();
-        $this->metadata[self::METADATA_ENTITY_TYPE] = $entityId::class;
-        $this->metadata[self::METADATA_ENTITY_ID] = $entityId->toString();
+        $this->metadata = [
+            self::METADATA_UUID => $uuid->toString(),
+            self::METADATA_NAME => $name,
+            self::METADATA_PRODUCER_TYPE => $producerId::class,
+            self::METADATA_PRODUCER_ID => $producerId->toString(),
+            self::METADATA_ENTITY_TYPE => $entityId::class,
+            self::METADATA_ENTITY_ID => $entityId->toString(),
+        ];
         if (null !== $version) {
             $this->metadata[self::METADATA_VERSION] = $version;
         }
     }
 
     /**
-     * @return Envelope<T>
+     * @template TEvent of Event
+     * @param TEvent $message
+     *
+     * @return self<TEvent>
      */
     public static function new(Event $message, Domain\Id $producerId, ?int $version = null): self
     {
@@ -61,18 +80,15 @@ public static function new(Event $message, Domain\Id $producerId, ?int $version
 
     public function uuid(): UUID
     {
-        return new UUID($this->get(self::METADATA_UUID));
+        return new UUID($this->metadata[self::METADATA_UUID]);
     }
 
     public function name(): string
     {
-        return $this->get(self::METADATA_NAME);
+        return $this->metadata[self::METADATA_NAME];
     }
 
-    /**
-     * @return T
-     */
-    public function message(): Event
+    public function message()
     {
         return $this->message;
     }
@@ -84,7 +100,7 @@ public function producerId(): Domain\Id
         /** @var class-string<Domain\Id> $class */
         /** @phpstan-var class-string<Domain\Id> $class */
         /** @psalm-var class-string<Domain\Id> $class */
-        return $class::fromString($this->get(self::METADATA_PRODUCER_ID));
+        return $class::fromString((string) $this->get(self::METADATA_PRODUCER_ID));
     }
 
     public function entityId(): Domain\Id
@@ -94,12 +110,12 @@ public function entityId(): Domain\Id
         /** @var class-string<Domain\Id> $class */
         /** @phpstan-var class-string<Domain\Id> $class */
         /** @psalm-var class-string<Domain\Id> $class */
-        return $class::fromString($this->get(self::METADATA_ENTITY_ID));
+        return $class::fromString((string) $this->get(self::METADATA_ENTITY_ID));
     }
 
     public function version(): ?int
     {
-        return $this->get(self::METADATA_VERSION);
+        return $this->metadata[self::METADATA_VERSION] ?? null;
     }
 
     public function set(string $name, $value): self

src/Domain/Event/Listener/Factory.php

@@ -15,20 +15,25 @@
 
 use Streak\Domain\Event;
 use Streak\Domain\Event\Exception\InvalidEventGiven;
-use Streak\Domain\Event\Listener;
 use Streak\Domain\Exception\InvalidIdGiven;
 
 /**
+ * @template T of Event\Listener
+ *
  * @author Alan Gabriel Bem <[email protected]>
  */
 interface Factory
 {
     /**
+     * @return T
+     *
      * @throws InvalidIdGiven
      */
-    public function create(Listener\Id $id): Listener;
+    public function create(Event\Listener\Id $id): Event\Listener;
 
     /**
+     * @return T
+     *
      * @throws InvalidEventGiven
      */
     public function createFor(Event\Envelope $event): Event\Listener;

src/Domain/Event/Sourced/Entity/Helper.php

@@ -42,7 +42,7 @@ public function applyEvent(Event\Envelope $event): void
     }
 
     /**
-     * @return Event\Sourced\Entity[]
+     * @return \Generator<int, Event\Sourced\Entity>
      */
     public function extractEventSourcedEntities(): iterable
     {
@@ -128,6 +128,8 @@ private static function applyEventByArgumentType(Event\Envelope $event, object &
 
     /**
      * Extract event sourced entities recursively.
+     *
+     * @return \Generator<int, Event\Sourced\Entity>
      */
     private static function doExtractEventSourcedEntities(object $object, array &$ignored = []): iterable
     {

src/Domain/Event/Stream.php

@@ -17,6 +17,8 @@
 
 /**
  * @author Alan Gabriel Bem <[email protected]>
+ *
+ * @psalm-immutable
  */
 interface Stream extends \Traversable
 {

src/Domain/Event/Subscription/Factory.php

@@ -16,9 +16,14 @@
 use Streak\Domain\Event;
 
 /**
+ * @template T of Event\Subscription
+ *
  * @author Alan Gabriel Bem <[email protected]>
  */
 interface Factory
 {
+    /**
+     * @return T
+     */
     public function create(Event\Listener $listener): Event\Subscription;
 }

src/Infrastructure/Domain/AggregateRoot/Snapshotter/Storage/RedisStorage.php

@@ -20,6 +20,8 @@
 
 /**
  * @author Alan Gabriel Bem <[email protected]>
+ *
+ * @see \Streak\Infrastructure\Domain\AggregateRoot\Snapshotter\Storage\RedisStorageTest
  */
 final class RedisStorage implements Storage, Resettable
 {
@@ -38,12 +40,17 @@ public function find(AggregateRoot $aggregate): string
             throw new SnapshotNotFound($aggregate);
         }
 
+        // Redis::get() can return Redis instance when it's in multi() mode.
+        if ($snapshot instanceof \Redis) {
+            throw new SnapshotNotFound($aggregate);
+        }
+
         return $snapshot;
     }
 
     public function store(AggregateRoot $aggregate, string $snapshot): void
     {
-        $this->redis->set($this->key($aggregate), (string) $snapshot);
+        $this->redis->set($this->key($aggregate), $snapshot);
     }
 
     public function reset(): bool

src/Infrastructure/Domain/Event/InMemoryStream.php

@@ -19,6 +19,8 @@
 /**
  * @author Alan Gabriel Bem <[email protected]>
  *
+ * @psalm-immutable
+ *
  * @see \Streak\Infrastructure\Domain\Event\InMemoryStreamTest
  */
 final class InMemoryStream implements \IteratorAggregate, Event\Stream

src/Infrastructure/Domain/Event/LoggingListener/Factory.php

@@ -18,6 +18,8 @@
 use Streak\Infrastructure\Domain\Event\LoggingListener;
 
 /**
+ * @implements Event\Listener\Factory<LoggingListener>
+ *
  * @author Alan Gabriel Bem <[email protected]>
  *
  * @see \Streak\Infrastructure\Domain\Event\LoggingListener\FactoryTest
@@ -28,14 +30,14 @@ public function __construct(private Event\Listener\Factory $factory, private Log
     {
     }
 
-    public function create(Event\Listener\Id $id): Event\Listener
+    public function create(Event\Listener\Id $id): LoggingListener
     {
         $saga = $this->factory->create($id);
 
         return new LoggingListener($saga, $this->logger);
     }
 
-    public function createFor(Event\Envelope $event): Event\Listener
+    public function createFor(Event\Envelope $event): LoggingListener
     {
         $listener = $this->factory->createFor($event);
 

src/Infrastructure/Domain/Event/Sourced/Subscription/InMemoryState.php

@@ -55,7 +55,7 @@ public function get(string $name)
         return $this->state[$name];
     }
 
-    public function set(string $name, $value): State
+    public function set(string $name, $value): self
     {
         $this->validate($name, $value);
 

src/Infrastructure/Domain/Event/Subscription/CommittingSubscription/Factory.php

@@ -19,6 +19,8 @@
 use Streak\Infrastructure\Domain\UnitOfWork;
 
 /**
+ * @implements Event\Subscription\Factory<CommittingSubscription>
+ *
  * @author Alan Gabriel Bem <[email protected]>
  *
  * @see \Streak\Infrastructure\Domain\Event\Subscription\CommittingSubscription\FactoryTest
@@ -29,7 +31,7 @@ public function __construct(private Subscription\Factory $factory, private UnitO
     {
     }
 
-    public function create(Event\Listener $listener): Event\Subscription
+    public function create(Event\Listener $listener): CommittingSubscription
     {
         $subscription = $this->factory->create($listener);
 

src/Infrastructure/Domain/Event/Subscription/DAO.php

@@ -30,7 +30,7 @@ public function exists(Listener\Id $id): bool;
     /**
      * @param string[] $types
      *
-     * @return DAO\Subscription[]
+     * @return iterable<int,Subscription>
      */
     public function all(array $types = [], ?bool $completed = null): iterable;
 }

src/Infrastructure/Domain/Event/Subscription/DAO/DbalPostgresDAO.php

@@ -30,8 +30,13 @@
  */
 class DbalPostgresDAO implements DAO
 {
-    public function __construct(private Subscription\Factory $subscriptions, private Event\Listener\Factory $listeners, private Connection $connection, private Event\Converter $converter)
-    {
+    public function __construct(
+        /** @var Subscription\Factory<DAO\Subscription> */
+        private Subscription\Factory $subscriptions,
+        private Event\Listener\Factory $listeners,
+        private Connection $connection,
+        private Event\Converter $converter
+    ) {
     }
 
     /**
@@ -69,11 +74,9 @@ public function exists(Listener\Id $id): bool
     }
 
     /**
-     * @param string[] $types
+     * @return \Generator<int, Subscription>
      *
      * @throws \Doctrine\DBAL\DBALException
-     *
-     * @return Subscription[]
      */
     public function all(array $types = [], ?bool $completed = null): iterable
     {
@@ -186,7 +189,7 @@ public function drop(): void
         $statement->execute();
     }
 
-    private function fromRow($row): Subscription
+    private function fromRow($row): DAO\Subscription
     {
         $id = $row['subscription_type'];
         $id = $id::fromString($row['subscription_id']);
@@ -306,11 +309,9 @@ private function doSave(DAO\Subscription $subscription): void
     }
 
     /**
-     *
      * @throws \Doctrine\DBAL\DBALException
-     * @return \Streak\Infrastructure\Domain\Event\Subscription\DAO\Subscription|null
      */
-    private function doOne(Event\Listener\Id $id)
+    private function doOne(Event\Listener\Id $id): ?DAO\Subscription
     {
         $sql = 'SELECT subscription_type, subscription_id, subscription_version, state, started_by, started_at, last_processed_event, last_event_processed_at, completed, paused_at FROM subscriptions WHERE subscription_type = :subscription_type AND subscription_id = :subscription_id LIMIT 1';
 
@@ -354,6 +355,8 @@ private function doExists(Listener\Id $id): bool
     }
 
     /**
+     * @return \Generator<int, Subscription>
+     *
      * @throws \Doctrine\DBAL\DBALException
      */
     private function doAll(array $types, ?bool $completed): \Generator