Feat: Default context (#45)

doc/getting-started.md

@@ -71,6 +71,22 @@ If you use callables, it will be injected as well.
 The `ETLState` object is also injected into all events.
 Most of its properties are read-only, except `context`.
 
+> [!TIP]
+> Your executor can provide a default context (see example below).
+
+```php
+it('accepts a default context', function () {
+    // Given
+    $executor = (new EtlExecutor())->withContext(['foo' => 'bar']);
+
+    // When
+    $report = $executor->process([], context: ['bar' => 'baz']);
+
+    // Then
+    expect($report->context)->toBe(['foo' => 'bar', 'bar' => 'baz']);
+});
+```
+
 Skipping items
 --------------
 

src/EtlExecutor.php

@@ -56,12 +56,16 @@ final class EtlExecutor implements EventDispatcherInterface
 
     private EventDispatcher $eventDispatcher;
 
+    /**
+     * @param array<string, mixed> $context
+     */
     public function __construct(
         public readonly ExtractorInterface $extractor = new IterableExtractor(),
         public readonly TransformerInterface $transformer = new NullTransformer(),
         public readonly LoaderInterface $loader = new InMemoryLoader(),
         public readonly EtlConfiguration $options = new EtlConfiguration(),
         public readonly ProcessorInterface $processor = new IterableProcessor(),
+        public readonly array $context = [],
     ) {
         $this->listenerProvider = new PrioritizedListenerProvider();
         $this->eventDispatcher = new EventDispatcher($this->listenerProvider);
@@ -74,7 +78,12 @@ public function __construct(
      */
     public function process(mixed $source = null, mixed $destination = null, array $context = []): EtlState
     {
-        $state = new EtlState(options: $this->options, source: $source, destination: $destination, context: $context);
+        $state = new EtlState(
+            options: $this->options,
+            source: $source,
+            destination: $destination,
+            context: [...$this->context, ...$context]
+        );
 
         try {
             $this->emit(InitEvent::class, $state);

src/Internal/EtlBuilderTrait.php

@@ -108,4 +108,12 @@ public function withProcessor(ProcessorInterface $processor): self
     {
         return $this->cloneWith(['processor' => $processor]);
     }
+
+    /**
+     * @param array<string, mixed> $context
+     */
+    public function withContext(array $context): self
+    {
+        return $this->cloneWith(['context' => $context]);
+    }
 }

tests/Unit/EtlExecutorTest.php

@@ -114,3 +114,14 @@ public function process(EtlExecutor $executor, EtlState $state, mixed $extracted
     // When
     $executor->process([]);
 })->throws(ExtractException::class);
+
+it('accepts a default context', function () {
+    // Given
+    $executor = (new EtlExecutor())->withContext(['foo' => 'bar']);
+
+    // When
+    $report = $executor->process([], context: ['bar' => 'baz']);
+
+    // Then
+    expect($report->context)->toBe(['foo' => 'bar', 'bar' => 'baz']);
+});