bug #868 [Agent] Fix sources metadata unavailable during streaming (OskarStark)

This PR was merged into the main branch.

Discussion
----------

[Agent] Fix sources metadata unavailable during streaming

  | Q             | A
  | ------------- | ---
  | Bug fix?      | yes
  | New feature?  | no
  | Docs?         | no
  | Issues        | Fix #833
  | License       | MIT

Replaces
* #838

Commits
-------

aeb6e22 [Agent] Fix sources metadata unavailable during streaming

Author: OskarStark

src/agent/src/Toolbox/StreamResult.php

@@ -31,7 +31,22 @@ public function getContent(): \Generator
         $streamedResult = '';
         foreach ($this->generator as $value) {
             if ($value instanceof ToolCallResult) {
-                yield from ($this->handleToolCallsCallback)($value, Message::ofAssistant($streamedResult))->getContent();
+                $innerResult = ($this->handleToolCallsCallback)($value, Message::ofAssistant($streamedResult));
+
+                // Propagate metadata from inner result to this result
+                foreach ($innerResult->getMetadata()->all() as $key => $metadataValue) {
+                    $this->getMetadata()->add($key, $metadataValue);
+                }
+
+                $content = $innerResult->getContent();
+                // Strings are iterable in PHP but yield from would iterate character-by-character.
+                // We need to yield the complete string as a single value to preserve streaming behavior.
+                // null should also be yielded as-is.
+                if (\is_string($content) || null === $content || !is_iterable($content)) {
+                    yield $content;
+                } else {
+                    yield from $content;
+                }
 
                 break;
             }

src/agent/tests/Toolbox/AgentProcessorTest.php

@@ -26,6 +26,7 @@
 use Symfony\AI\Platform\PlatformInterface;
 use Symfony\AI\Platform\Result\DeferredResult;
 use Symfony\AI\Platform\Result\InMemoryRawResult;
+use Symfony\AI\Platform\Result\StreamResult as GenericStreamResult;
 use Symfony\AI\Platform\Result\TextResult;
 use Symfony\AI\Platform\Result\ToolCall;
 use Symfony\AI\Platform\Result\ToolCallResult;
@@ -233,4 +234,52 @@ public function testSourcesGetCollectedAcrossConsecutiveToolCalls()
         $this->assertCount(2, $metadata->get('sources'));
         $this->assertSame([$source1, $source2], $metadata->get('sources'));
     }
+
+    public function testSourcesEndUpInResultMetadataWithStreaming()
+    {
+        $toolCall = new ToolCall('call_1234', 'tool_sources', ['arg1' => 'value1']);
+        $source1 = new Source('Relevant Article 1', 'http://example.com/article1', 'Content of article about the topic');
+        $source2 = new Source('Relevant Article 2', 'http://example.com/article2', 'More content of article about the topic');
+        $toolbox = $this->createMock(ToolboxInterface::class);
+        $toolbox
+            ->expects($this->once())
+            ->method('execute')
+            ->willReturn(new ToolResult($toolCall, 'Response based on the two articles.', [$source1, $source2]));
+
+        $messageBag = new MessageBag();
+
+        // Create a generator that yields chunks and then a ToolCallResult
+        $generator = (function () use ($toolCall) {
+            yield 'chunk1';
+            yield 'chunk2';
+            yield new ToolCallResult($toolCall);
+        })();
+
+        $result = new GenericStreamResult($generator);
+
+        $agent = $this->createMock(AgentInterface::class);
+        $agent
+            ->expects($this->once())
+            ->method('call')
+            ->willReturn(new TextResult('Final response based on the two articles.'));
+
+        $processor = new AgentProcessor($toolbox, includeSources: true);
+        $processor->setAgent($agent);
+
+        $output = new Output('gpt-4', $result, $messageBag);
+
+        $processor->processOutput($output);
+
+        // Consume the stream
+        $content = '';
+        foreach ($output->getResult()->getContent() as $chunk) {
+            $content .= $chunk;
+        }
+
+        // After consuming the stream, metadata should be available
+        $metadata = $output->getResult()->getMetadata();
+        $this->assertTrue($metadata->has('sources'));
+        $this->assertCount(2, $metadata->get('sources'));
+        $this->assertSame([$source1, $source2], $metadata->get('sources'));
+    }
 }