Fix issue in PromptSummaryEngine

CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 - Parsing streaming response with some OpenAi compatible services.
+- Issue in `PromptSummaryEngine` if there are no artifacts during recursive summarization.
 
 **Note**: This release includes breaking changes. Please refer to the [Migration Guide](./MIGRATION.md#030x-to-031x) for details.
 

griptape/engines/summary/prompt_summary_engine.py

@@ -60,6 +60,11 @@ def summarize_artifacts_rec(
         summary: Optional[str] = None,
         rulesets: Optional[list[Ruleset]] = None,
     ) -> TextArtifact:
+        if not artifacts:
+            if summary is None:
+                raise ValueError("No artifacts to summarize")
+            return TextArtifact(summary)
+
         artifacts_text = self.chunk_joiner.join([a.to_text() for a in artifacts])
 
         system_prompt = self.system_template_generator.render(

tests/unit/engines/summary/test_prompt_summary_engine.py

@@ -42,3 +42,10 @@ def copy_test_resource(resource_path: str):
             return Path(full_path).read_text()
 
         assert engine.summarize_text(copy_test_resource("test.txt") * 50)
+
+    def test_summarize_artifacts_rec_no_artifacts(self, engine):
+        with pytest.raises(ValueError):
+            engine.summarize_artifacts_rec([])
+
+        output = engine.summarize_artifacts_rec([], "summary")
+        assert output.value == "summary"