Add a reader decorator that allows adding array metadata to decorated read data

src/batch/src/Job/Item/Reader/AddMetadataReader.php

@@ -0,0 +1,72 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Yokai\Batch\Job\Item\Reader;
+
+use Generator;
+use Yokai\Batch\Exception\UnexpectedValueException;
+use Yokai\Batch\Job\Item\ElementConfiguratorTrait;
+use Yokai\Batch\Job\Item\FlushableInterface;
+use Yokai\Batch\Job\Item\InitializableInterface;
+use Yokai\Batch\Job\Item\ItemReaderInterface;
+use Yokai\Batch\Job\JobExecutionAwareInterface;
+use Yokai\Batch\Job\JobExecutionAwareTrait;
+
+final class AddMetadataReader implements
+    ItemReaderInterface,
+    InitializableInterface,
+    FlushableInterface,
+    JobExecutionAwareInterface
+{
+    use ElementConfiguratorTrait;
+    use JobExecutionAwareTrait;
+
+    private ItemReaderInterface $reader;
+
+    /**
+     * @phpstan-var array<string, mixed>
+     */
+    private array $metadata;
+
+    /**
+     * @phpstan-param array<string, mixed> $metadata
+     */
+    public function __construct(ItemReaderInterface $reader, array $metadata)
+    {
+        $this->reader = $reader;
+        $this->metadata = $metadata;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function initialize(): void
+    {
+        $this->configureElementJobContext($this->reader, $this->jobExecution);
+        $this->initializeElement($this->reader);
+    }
+
+    /**
+     * @inheritdoc
+     * @phpstan-return Generator<array<mixed>>
+     */
+    public function read(): Generator
+    {
+        foreach ($this->reader->read() as $item) {
+            if (!\is_array($item)) {
+                throw UnexpectedValueException::type('array', $item);
+            }
+
+            yield $this->metadata + $item;
+        }
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function flush(): void
+    {
+        $this->flushElement($this->reader);
+    }
+}

src/batch/tests/Job/Item/Reader/AddMetadataReaderTest.php

@@ -0,0 +1,46 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Yokai\Batch\Tests\Job\Item\Reader;
+
+use PHPUnit\Framework\TestCase;
+use Yokai\Batch\Exception\UnexpectedValueException;
+use Yokai\Batch\Job\Item\Reader\AddMetadataReader;
+use Yokai\Batch\Job\Item\Reader\StaticIterableReader;
+use Yokai\Batch\JobExecution;
+
+class AddMetadataReaderTest extends TestCase
+{
+    public function testRead(): void
+    {
+        $reader = new AddMetadataReader(
+            new StaticIterableReader([['name' => 'John'], ['name' => 'Jane']]),
+            ['_type' => 'user']
+        );
+
+        $reader->setJobExecution(JobExecution::createRoot('123456', 'test'));
+        $reader->initialize();
+        $read = \iterator_to_array($reader->read());
+        $reader->flush();
+
+        self::assertSame(
+            [['_type' => 'user', 'name' => 'John'], ['_type' => 'user', 'name' => 'Jane']],
+            $read
+        );
+    }
+
+    public function testReadDecoratedNotReturningAnArray(): void
+    {
+        $this->expectException(UnexpectedValueException::class);
+
+        $reader = new AddMetadataReader(
+            new StaticIterableReader(['string']),
+            ['_type' => 'user']
+        );
+
+        $reader->setJobExecution(JobExecution::createRoot('123456', 'test'));
+        $reader->initialize();
+        \iterator_to_array($reader->read());
+    }
+}