fix: edge cases in metrics

src/ragas/metrics/_context_recall.py

@@ -58,6 +58,16 @@
                 "Attributed": "1",
             },
         },
+        {
+            "question": """What is the primary fuel for the Sun?""",
+            "context": """NULL""",
+            "answer": """Hydrogen""",
+            "classification": {
+                "statement_1": "The Sun's primary fuel is hydrogen.",
+                "reason": "The context contains no information",
+                "Attributed": "0",
+            },
+        },
     ],
     input_keys=["question", "context", "answer"],
     output_key="classification",

src/ragas/metrics/_faithfulness.py

@@ -187,7 +187,7 @@ async def _ascore(
             is_async=is_async,
         )
 
-        assert isinstance(statements, dict), "Invalid JSON response"
+        statements = statements if isinstance(statements, dict) else {}
         p = self._create_nli_prompt(row, statements.get("statements", []))
         nli_result = await self.llm.generate(p, callbacks=callbacks, is_async=is_async)
         json_output = await json_loader.safe_load(