fix: handle edge cases in prompt processing (#374)

Author: shahules786

src/ragas/metrics/_answer_correctness.py

@@ -119,15 +119,21 @@ def _score_batch(
         f1_score = []
         for prediction in outputs:
             prediction = json_loader.safe_load(prediction[0].text, self.llm)
-            prediction = [
-                item.get(key_map[k], np.nan)
-                for item in prediction
-                for k in key_map.keys()
-            ]
-            tp, fp, fn = [
-                len(item) if isinstance(item, list) else np.nan for item in prediction
-            ]
-            score = tp / (tp + 0.5 * (fp + fn))
+            prediction = prediction if isinstance(prediction, list) else []
+            if prediction:
+                prediction = [
+                    item.get(key_map[k], np.nan)
+                    for item in prediction
+                    for k in key_map.keys()
+                ]
+                tp, fp, fn = [
+                    len(item) if isinstance(item, list) else np.nan
+                    for item in prediction
+                ]
+                score = tp / (tp + 0.5 * (fp + fn))
+            else:
+                score = np.nan
+
             f1_score.append(score)
 
         similarity_scores = self.answer_similarity._score_batch(dataset)  # type: ignore

src/ragas/metrics/_faithfulness.py

@@ -173,7 +173,7 @@ def _score_batch(
             scores = []
             for output in outputs:
                 output = json_loader.safe_load(output[0].text, self.llm)
-                output = output if output else []
+                output = output if isinstance(output, list) else []
                 faithful_statements = sum(
                     verdict_score_map.get(dict.get("verdict", "").lower(), np.nan)
                     for dict in output

src/ragas/utils.py

@@ -111,7 +111,7 @@ def _fix_to_json(
         callbacks: t.Optional[CallbackManager] = None,
         callback_group_name: str = "batch",
     ):
-       # TODO (executor)
+        # TODO (executor)
         with trace_as_chain_group(
             callback_group_name, callback_manager=callbacks
         ) as batch_group: