TASK: Ensure that Events are never instantiated empty

by enforcing this via "non-empty-array" we can better catch runtime type errors beforehand via phpstan. As otherwise the event store will fail with

> Writable events must contain at least one event

Some internal utility methods previously also returned possibly empty "Events" instances which were then transformed via iterator_to_array back to arrays and merged. This was not simplified to just work with arrays directly to denote that they might be empty. In cases were we work with fully sure filled intermediate event arrays we use non-empty-array.

With this now fine-grained type checking aside from the original found set properties error following cases will also break with 0 events:

- handleSetSerializedNodeProperties (known)
- handleSetSerializedNodeReferences
- handlePublishWorkspace and handlePublishIndividualNodesFromWorkspace if there were no applied events that implement PublishableToWorkspaceInterface -> goes into direction of neos#5337
- structure adjustment TETHERED_NODE_WRONGLY_ORDERED

Neos.ContentRepository.Core/Classes/EventStore/Events.php

@@ -10,16 +10,17 @@
  * @implements \IteratorAggregate<EventInterface|DecoratedEvent>
  * @internal only used during event publishing (from within command handlers) - and their implementation is not API
  */
-final class Events implements \IteratorAggregate, \Countable
+final readonly class Events implements \IteratorAggregate, \Countable
 {
     /**
-     * @var array<EventInterface|DecoratedEvent>
+     * @var non-empty-array<EventInterface|DecoratedEvent>
      */
-    private readonly array $events;
+    public array $items;
 
     private function __construct(EventInterface|DecoratedEvent ...$events)
     {
-        $this->events = $events;
+        /** @var non-empty-array<EventInterface|DecoratedEvent> $events */
+        $this->items = $events;
     }
 
     public static function with(EventInterface|DecoratedEvent $event): self
@@ -29,11 +30,11 @@ public static function with(EventInterface|DecoratedEvent $event): self
 
     public function withAppendedEvents(Events $events): self
     {
-        return new self(...$this->events, ...$events->events);
+        return new self(...$this->items, ...$events->items);
     }
 
     /**
-     * @param array<EventInterface|DecoratedEvent> $events
+     * @param non-empty-array<EventInterface|DecoratedEvent> $events
      * @return static
      */
     public static function fromArray(array $events): self
@@ -43,21 +44,21 @@ public static function fromArray(array $events): self
 
     public function getIterator(): \Traversable
     {
-        yield from $this->events;
+        yield from $this->items;
     }
 
     /**
      * @template T
      * @param \Closure(EventInterface|DecoratedEvent $event): T $callback
-     * @return list<T>
+     * @return non-empty-list<T>
      */
     public function map(\Closure $callback): array
     {
-        return array_map($callback, $this->events);
+        return array_map($callback, $this->items);
     }
 
     public function count(): int
     {
-        return count($this->events);
+        return count($this->items);
     }
 }

Neos.ContentRepository.Core/Classes/Feature/Common/NodeTypeChangeInternals.php

@@ -16,7 +16,7 @@
 
 use Neos\ContentRepository\Core\DimensionSpace\DimensionSpacePointSet;
 use Neos\ContentRepository\Core\DimensionSpace\OriginDimensionSpacePointSet;
-use Neos\ContentRepository\Core\EventStore\Events;
+use Neos\ContentRepository\Core\EventStore\EventInterface;
 use Neos\ContentRepository\Core\Feature\NodeRemoval\Event\NodeAggregateWasRemoved;
 use Neos\ContentRepository\Core\NodeType\NodeType;
 use Neos\ContentRepository\Core\Projection\ContentGraph\ContentGraphInterface;
@@ -34,13 +34,15 @@ trait NodeTypeChangeInternals
     /**
      * NOTE: when changing this method, {@see NodeTypeChange::requireConstraintsImposedByHappyPathStrategyAreMet}
      * needs to be modified as well (as they are structurally the same)
+     *
+     * @return array<EventInterface>
      */
     private function deleteDisallowedNodesWhenChangingNodeType(
         ContentGraphInterface $contentGraph,
         NodeAggregate $nodeAggregate,
         NodeType $newNodeType,
         NodeAggregateIds &$alreadyRemovedNodeAggregateIds,
-    ): Events {
+    ): array {
         $events = [];
         // if we have children, we need to check whether they are still allowed
         // after we changed the node type of the $nodeAggregate to $newNodeType.
@@ -117,15 +119,18 @@ private function deleteDisallowedNodesWhenChangingNodeType(
             }
         }
 
-        return Events::fromArray($events);
+        return $events;
     }
 
+    /**
+     * @return array<EventInterface>
+     */
     private function deleteObsoleteTetheredNodesWhenChangingNodeType(
         ContentGraphInterface $contentGraph,
         NodeAggregate $nodeAggregate,
         NodeType $newNodeType,
         NodeAggregateIds &$alreadyRemovedNodeAggregateIds,
-    ): Events {
+    ): array {
         $events = [];
         // find disallowed tethered nodes
         $tetheredNodeAggregates = $contentGraph->findTetheredChildNodeAggregates($nodeAggregate->nodeAggregateId);
@@ -156,7 +161,7 @@ private function deleteObsoleteTetheredNodesWhenChangingNodeType(
             }
         }
 
-        return Events::fromArray($events);
+        return $events;
     }
 
     /**

Neos.ContentRepository.Core/Classes/Feature/Common/NodeVariationInternals.php

@@ -89,7 +89,7 @@ protected function handleCreateNodeSpecializationVariant(
 
     /**
      * @param array<int,EventInterface> $events
-     * @return array<int,EventInterface>
+     * @return non-empty-array<int,EventInterface>
      */
     protected function collectNodeSpecializationVariantsThatWillHaveBeenCreated(
         ContentGraphInterface $contentGraph,
@@ -152,7 +152,7 @@ protected function handleCreateNodeGeneralizationVariant(
 
     /**
      * @param array<int,EventInterface> $events
-     * @return array<int,EventInterface>
+     * @return non-empty-array<int,EventInterface>
      */
     protected function collectNodeGeneralizationVariantsThatWillHaveBeenCreated(
         ContentGraphInterface $contentGraph,
@@ -215,7 +215,7 @@ protected function handleCreateNodePeerVariant(
 
     /**
      * @param array<int,EventInterface> $events
-     * @return array<int,EventInterface>
+     * @return non-empty-array<int,EventInterface>
      */
     protected function collectNodePeerVariantsThatWillHaveBeenCreated(
         ContentGraphInterface $contentGraph,

Neos.ContentRepository.Core/Classes/Feature/Common/TetheredNodeInternals.php

@@ -17,6 +17,7 @@
 use Neos\ContentRepository\Core\DimensionSpace\OriginDimensionSpacePoint;
 use Neos\ContentRepository\Core\DimensionSpace\OriginDimensionSpacePointSet;
 use Neos\ContentRepository\Core\DimensionSpace\VariantType;
+use Neos\ContentRepository\Core\EventStore\EventInterface;
 use Neos\ContentRepository\Core\EventStore\Events;
 use Neos\ContentRepository\Core\Feature\NodeCreation\Dto\NodeAggregateIdsByNodePaths;
 use Neos\ContentRepository\Core\Feature\NodeCreation\Event\NodeAggregateWithNodeWasCreated;
@@ -164,6 +165,9 @@ protected function createEventsForMissingTetheredNode(
         );
     }
 
+    /**
+     * @return array<EventInterface>
+     */
     protected function createEventsForMissingTetheredNodeAggregate(
         ContentGraphInterface $contentGraph,
         TetheredNodeTypeDefinition $tetheredNodeTypeDefinition,
@@ -173,7 +177,7 @@ protected function createEventsForMissingTetheredNodeAggregate(
         ?NodeAggregateId $succeedingSiblingNodeAggregateId,
         NodeAggregateIdsByNodePaths $nodeAggregateIdsByNodePaths,
         NodePath $currentNodePath,
-    ): Events {
+    ): array {
         $events = [];
         $tetheredNodeType = $this->requireNodeType($tetheredNodeTypeDefinition->nodeTypeName);
         $nodeAggregateId = $nodeAggregateIdsByNodePaths->getNodeAggregateId($currentNodePath) ?? NodeAggregateId::create();
@@ -243,22 +247,20 @@ protected function createEventsForMissingTetheredNodeAggregate(
         foreach ($tetheredNodeType->tetheredNodeTypeDefinitions as $childTetheredNodeTypeDefinition) {
             $events = array_merge(
                 $events,
-                iterator_to_array(
-                    $this->createEventsForMissingTetheredNodeAggregate(
-                        $contentGraph,
-                        $childTetheredNodeTypeDefinition,
-                        $affectedOriginDimensionSpacePoints,
-                        $coverageByOrigin,
-                        $nodeAggregateId,
-                        null,
-                        $nodeAggregateIdsByNodePaths,
-                        $currentNodePath->appendPathSegment($childTetheredNodeTypeDefinition->name),
-                    )
+                $this->createEventsForMissingTetheredNodeAggregate(
+                    $contentGraph,
+                    $childTetheredNodeTypeDefinition,
+                    $affectedOriginDimensionSpacePoints,
+                    $coverageByOrigin,
+                    $nodeAggregateId,
+                    null,
+                    $nodeAggregateIdsByNodePaths,
+                    $currentNodePath->appendPathSegment($childTetheredNodeTypeDefinition->name),
                 )
             );
         }
 
-        return Events::fromArray($events);
+        return $events;
     }
 
     protected function createEventsForWronglyTypedNodeAggregate(
@@ -311,21 +313,17 @@ protected function createEventsForWronglyTypedNodeAggregate(
 
         // remove disallowed nodes
         if ($conflictResolutionStrategy === NodeAggregateTypeChangeChildConstraintConflictResolutionStrategy::STRATEGY_DELETE) {
-            array_push($events, ...iterator_to_array(
-                $this->deleteDisallowedNodesWhenChangingNodeType(
-                    $contentGraph,
-                    $nodeAggregate,
-                    $tetheredNodeType,
-                    $alreadyRemovedNodeAggregateIds
-                )
+            array_push($events, ...$this->deleteDisallowedNodesWhenChangingNodeType(
+                $contentGraph,
+                $nodeAggregate,
+                $tetheredNodeType,
+                $alreadyRemovedNodeAggregateIds
             ));
-            array_push($events, ...iterator_to_array(
-                $this->deleteObsoleteTetheredNodesWhenChangingNodeType(
-                    $contentGraph,
-                    $nodeAggregate,
-                    $tetheredNodeType,
-                    $alreadyRemovedNodeAggregateIds
-                )
+            array_push($events, ...$this->deleteObsoleteTetheredNodesWhenChangingNodeType(
+                $contentGraph,
+                $nodeAggregate,
+                $tetheredNodeType,
+                $alreadyRemovedNodeAggregateIds
             ));
         }
 
@@ -338,7 +336,7 @@ protected function createEventsForWronglyTypedNodeAggregate(
             if ($tetheredChildNodeAggregate === null) {
                 $events = array_merge(
                     $events,
-                    iterator_to_array($this->createEventsForMissingTetheredNodeAggregate(
+                    $this->createEventsForMissingTetheredNodeAggregate(
                         $contentGraph,
                         $childTetheredNodeTypeDefinition,
                         $nodeAggregate->occupiedDimensionSpacePoints,
@@ -347,7 +345,7 @@ protected function createEventsForWronglyTypedNodeAggregate(
                         null,
                         $nodeAggregateIdsByNodePaths,
                         $currentNodePath->appendPathSegment($childTetheredNodeTypeDefinition->name),
-                    ))
+                    )
                 );
             } elseif (!$tetheredChildNodeAggregate->nodeTypeName->equals($childTetheredNodeTypeDefinition->nodeTypeName)) {
                 $events = array_merge($events, iterator_to_array(

Neos.ContentRepository.Core/Classes/Feature/NodeCreation/NodeCreation.php

@@ -17,6 +17,7 @@
 use Neos\ContentRepository\Core\CommandHandler\CommandHandlingDependencies;
 use Neos\ContentRepository\Core\DimensionSpace;
 use Neos\ContentRepository\Core\DimensionSpace\DimensionSpacePointSet;
+use Neos\ContentRepository\Core\EventStore\EventInterface;
 use Neos\ContentRepository\Core\EventStore\Events;
 use Neos\ContentRepository\Core\EventStore\EventsToPublish;
 use Neos\ContentRepository\Core\Feature\Common\InterdimensionalSiblings;
@@ -212,15 +213,15 @@ private function handleCreateNodeAggregateWithNodeAndSerializedProperties(
             )
         ];
 
-        array_push($events, ...iterator_to_array($this->handleTetheredChildNodes(
+        array_push($events, ...$this->handleTetheredChildNodes(
             $command,
             $contentGraph,
             $nodeType,
             $coveredDimensionSpacePoints,
             $command->nodeAggregateId,
             $descendantNodeAggregateIds,
             null
-        )));
+        ));
 
         return new EventsToPublish(
             ContentStreamEventStreamName::fromContentStreamId($contentGraph->getContentStreamId())
@@ -261,6 +262,7 @@ private function createRegularWithNode(
     /**
      * @throws ContentStreamDoesNotExistYet
      * @throws NodeTypeNotFound
+     * @return array<EventInterface>
      */
     private function handleTetheredChildNodes(
         CreateNodeAggregateWithNodeAndSerializedProperties $command,
@@ -270,7 +272,7 @@ private function handleTetheredChildNodes(
         NodeAggregateId $parentNodeAggregateId,
         NodeAggregateIdsByNodePaths $nodeAggregateIds,
         ?NodePath $nodePath
-    ): Events {
+    ): array {
         $events = [];
         foreach ($nodeType->tetheredNodeTypeDefinitions as $tetheredNodeTypeDefinition) {
             $childNodeType = $this->requireNodeType($tetheredNodeTypeDefinition->nodeTypeName);
@@ -298,17 +300,17 @@ private function handleTetheredChildNodes(
                 SerializedNodeReferences::createEmpty(),
             );
 
-            array_push($events, ...iterator_to_array($this->handleTetheredChildNodes(
+            array_push($events, ...$this->handleTetheredChildNodes(
                 $command,
                 $contentGraph,
                 $childNodeType,
                 $coveredDimensionSpacePoints,
                 $childNodeAggregateId,
                 $nodeAggregateIds,
                 $childNodePath
-            )));
+            ));
         }
 
-        return Events::fromArray($events);
+        return $events;
     }
 }

Neos.ContentRepository.Core/Classes/Feature/NodeTypeChange/NodeTypeChange.php

@@ -17,6 +17,7 @@
 use Neos\ContentRepository\Core\CommandHandler\CommandHandlingDependencies;
 use Neos\ContentRepository\Core\DimensionSpace\OriginDimensionSpacePoint;
 use Neos\ContentRepository\Core\DimensionSpace\OriginDimensionSpacePointSet;
+use Neos\ContentRepository\Core\EventStore\EventInterface;
 use Neos\ContentRepository\Core\EventStore\Events;
 use Neos\ContentRepository\Core\EventStore\EventsToPublish;
 use Neos\ContentRepository\Core\Feature\RebaseableCommand;
@@ -90,6 +91,9 @@ abstract protected function areNodeTypeConstraintsImposedByGrandparentValid(
         NodeType $nodeType
     ): bool;
 
+    /**
+     * @return array<EventInterface>
+     */
     abstract protected function createEventsForMissingTetheredNodeAggregate(
         ContentGraphInterface $contentGraph,
         TetheredNodeTypeDefinition $tetheredNodeTypeDefinition,
@@ -99,7 +103,7 @@ abstract protected function createEventsForMissingTetheredNodeAggregate(
         ?NodeAggregateId $succeedingSiblingNodeAggregateId,
         NodeAggregateIdsByNodePaths $nodeAggregateIdsByNodePaths,
         NodePath $currentNodePath,
-    ): Events;
+    ): array;
 
     abstract protected function createEventsForWronglyTypedNodeAggregate(
         ContentGraphInterface $contentGraph,
@@ -230,18 +234,18 @@ private function handleChangeNodeAggregateType(
         // remove disallowed nodes
         $alreadyRemovedNodeAggregateIds = NodeAggregateIds::createEmpty();
         if ($command->strategy === NodeAggregateTypeChangeChildConstraintConflictResolutionStrategy::STRATEGY_DELETE) {
-            array_push($events, ...iterator_to_array($this->deleteDisallowedNodesWhenChangingNodeType(
+            array_push($events, ...$this->deleteDisallowedNodesWhenChangingNodeType(
                 $contentGraph,
                 $nodeAggregate,
                 $newNodeType,
                 $alreadyRemovedNodeAggregateIds,
-            )));
-            array_push($events, ...iterator_to_array($this->deleteObsoleteTetheredNodesWhenChangingNodeType(
+            ));
+            array_push($events, ...$this->deleteObsoleteTetheredNodesWhenChangingNodeType(
                 $contentGraph,
                 $nodeAggregate,
                 $newNodeType,
                 $alreadyRemovedNodeAggregateIds
-            )));
+            ));
         }
 
         // handle (missing) tethered node aggregates
@@ -254,7 +258,7 @@ private function handleChangeNodeAggregateType(
         foreach ($newNodeType->tetheredNodeTypeDefinitions as $tetheredNodeTypeDefinition) {
             $tetheredNodeAggregate = $contentGraph->findChildNodeAggregateByName($nodeAggregate->nodeAggregateId, $tetheredNodeTypeDefinition->name);
             if ($tetheredNodeAggregate === null) {
-                $events = array_merge($events, iterator_to_array($this->createEventsForMissingTetheredNodeAggregate(
+                $events = array_merge($events, $this->createEventsForMissingTetheredNodeAggregate(
                     $contentGraph,
                     $tetheredNodeTypeDefinition,
                     $nodeAggregate->occupiedDimensionSpacePoints,
@@ -263,7 +267,7 @@ private function handleChangeNodeAggregateType(
                     $succeedingSiblingIds[$tetheredNodeTypeDefinition->nodeTypeName->value] ?? null,
                     $command->tetheredDescendantNodeAggregateIds,
                     NodePath::fromNodeNames($tetheredNodeTypeDefinition->name)
-                )));
+                ));
             } elseif (!$tetheredNodeAggregate->nodeTypeName->equals($tetheredNodeTypeDefinition->nodeTypeName)) {
                 $events = array_merge($events, iterator_to_array($this->createEventsForWronglyTypedNodeAggregate(
                     $contentGraph,

Neos.ContentRepository.Core/Classes/Feature/RebaseableCommand.php

@@ -66,7 +66,7 @@ public static function enrichWithCommand(
         $processedEvents = [];
         $causationId = null;
         $i = 0;
-        foreach ($events as $event) {
+        foreach ($events->items as $event) {
             if ($event instanceof DecoratedEvent) {
                 $undecoratedEvent = $event->innerEvent;
                 if (!$undecoratedEvent instanceof PublishableToWorkspaceInterface) {