fix: restore classification of empty responses as refusals

Fixes #93

src/heretic/evaluator.py

@@ -67,7 +67,10 @@ class Evaluator:
     def count_refusals(self) -> int:
         refusal_count = 0
 
-        responses = self.model.get_responses_batched(self.bad_prompts)
+        responses = self.model.get_responses_batched(
+            self.bad_prompts,
+            skip_special_tokens=True,
+        )
 
         for prompt, response in zip(self.bad_prompts, responses):
             is_refusal = self.is_refusal(response)
@@ -78,6 +81,8 @@ class Evaluator:
                 print()
                 print(f"[bold]System prompt:[/] {prompt.system}")
                 print(f"[bold]Prompt:[/] {prompt.user}")
+                if not response.strip():
+                    response = "[italic]\\[empty][/]"
                 print(
                     f"[bold]Response:[/] [{'red' if is_refusal else 'green'}]{response}[/]"
                 )

src/heretic/model.py

@@ -514,30 +514,36 @@ class Model:
 
         return inputs, outputs
 
-    def get_responses(self, prompts: list[Prompt]) -> list[str]:
+    def get_responses(
+        self,
+        prompts: list[Prompt],
+        skip_special_tokens: bool = False,
+    ) -> list[str]:
         inputs, outputs = self.generate(
             prompts,
             max_new_tokens=self.settings.max_response_length,
         )
 
-        responses = self.tokenizer.batch_decode(
+        return self.tokenizer.batch_decode(
             # Extract the newly generated part.
             # This cast is valid because the input_ids property is a Tensor
             # if the tokenizer is invoked with return_tensors="pt", as above.
-            outputs[:, cast(Tensor, inputs["input_ids"]).shape[1] :]
+            outputs[:, cast(Tensor, inputs["input_ids"]).shape[1] :],
+            skip_special_tokens=skip_special_tokens,
         )
 
-        return [
-            # Strip out pad tokens from batch generation.
-            response.replace(self.tokenizer.pad_token, "")
-            for response in responses
-        ]
-
-    def get_responses_batched(self, prompts: list[Prompt]) -> list[str]:
+    def get_responses_batched(
+        self,
+        prompts: list[Prompt],
+        skip_special_tokens: bool = False,
+    ) -> list[str]:
         responses = []
 
         for batch in batchify(prompts, self.settings.batch_size):
-            for response in self.get_responses(batch):
+            for response in self.get_responses(
+                batch,
+                skip_special_tokens=skip_special_tokens,
+            ):
                 responses.append(response)
 
         return responses