fix: handle empty documents list in KnowledgeStorage.save() and asave()

Fixes #4277

When KnowledgeStorage.save() or asave() is called with an empty documents
list, the method now returns early instead of propagating a low-level
ValueError from ChromaDB's upsert operation.

This is a valid edge case that can occur in real-world workflows (e.g.,
after filtering, retrieval failures, or conditional logic), and should
be handled gracefully as a no-op.

Co-Authored-By: João <joao@crewai.com>

lib/crewai/src/crewai/knowledge/storage/knowledge_storage.py

@@ -99,6 +99,9 @@ class KnowledgeStorage(BaseKnowledgeStorage):
             )
 
     def save(self, documents: list[str]) -> None:
+        if not documents:
+            return
+
         try:
             client = self._get_client()
             collection_name = (
@@ -177,6 +180,9 @@ class KnowledgeStorage(BaseKnowledgeStorage):
         Args:
             documents: List of document strings to save.
         """
+        if not documents:
+            return
+
         try:
             client = self._get_client()
             collection_name = (

lib/crewai/tests/knowledge/test_knowledge_storage_integration.py

@@ -193,3 +193,40 @@ def test_dimension_mismatch_error_handling(mock_get_client: MagicMock) -> None:
 
     with pytest.raises(ValueError, match="Embedding dimension mismatch"):
         storage.save(["test document"])
+
+
+@patch("crewai.knowledge.storage.knowledge_storage.get_rag_client")
+def test_save_empty_documents_list(mock_get_client: MagicMock) -> None:
+    """Test that save() handles empty documents list gracefully.
+
+    Calling save() with an empty documents list should be a no-op and not
+    propagate low-level storage exceptions from ChromaDB.
+    """
+    mock_client = MagicMock()
+    mock_get_client.return_value = mock_client
+
+    storage = KnowledgeStorage(collection_name="empty_docs_test")
+
+    storage.save([])
+
+    mock_client.get_or_create_collection.assert_not_called()
+    mock_client.add_documents.assert_not_called()
+
+
+@pytest.mark.asyncio
+@patch("crewai.knowledge.storage.knowledge_storage.get_rag_client")
+async def test_asave_empty_documents_list(mock_get_client: MagicMock) -> None:
+    """Test that asave() handles empty documents list gracefully.
+
+    Calling asave() with an empty documents list should be a no-op and not
+    propagate low-level storage exceptions from ChromaDB.
+    """
+    mock_client = MagicMock()
+    mock_get_client.return_value = mock_client
+
+    storage = KnowledgeStorage(collection_name="empty_docs_async_test")
+
+    await storage.asave([])
+
+    mock_client.aget_or_create_collection.assert_not_called()
+    mock_client.aadd_documents.assert_not_called()