src/Executor/ReferenceExecutor.php
private function completeListValue(ListOfType $returnType, $fieldNodes, ResolveInfo $info, $path, &$result)
    {
        $itemType = $returnType->getWrappedType();
        Utils::invariant(
            is_array($result) || $result instanceof Traversable,
            'User Error: expected iterable, but did not find one for field ' . $info->parentType . '.' . $info->fieldName . '.'
        );
        $containsPromise = false;
        $i               = 0;
        $completedItems  = [];
        foreach ($result as $item) {
            $fieldPath     = $path;
            $fieldPath[]   = $i++;
            $completedItem = $this->completeValueCatchingError($itemType, $fieldNodes, $info, $fieldPath, $item);
            if (! $containsPromise && $this->getPromise($completedItem)) {
                $containsPromise = true;
            }
            $completedItems[] = $completedItem;
        }

        return $containsPromise ? $this->exeContext->promises->all($completedItems) : $completedItems;
    }
private function completeListValue(ListOfType $returnType, $fieldNodes, ResolveInfo $info, $path, &$result)
    {
        $itemType = $returnType->getWrappedType();
        Utils::invariant(
            is_array($result) || $result instanceof Traversable,
            'User Error: expected iterable, but did not find one for field ' . $info->parentType . '.' . $info->fieldName . '.'
        );
        $containsPromise = false;
        $i               = 0;
        $completedItems  = [];
        foreach ($result as $item) {
            $fieldPath     = $path;
            $fieldPath[]   = $i++;
            $completedItem = $this->completeValueCatchingError($itemType, $fieldNodes, $info, $fieldPath, $item);
            if (! $containsPromise && $this->getPromise($completedItem)) {
                $containsPromise = true;
            }
            $completedItems[] = $completedItem;
        }

        return $containsPromise ? $this->exeContext->promises->all($completedItems) : $completedItems;
    }
Complete a list value by completing each item in the list with the
inner type

@param FieldNode[] $fieldNodes
@param mixed[]     $path
@param mixed       $result

@return mixed[]|Promise

@throws Exception