fix failing test

src/transformers/models/recurrent_gemma/modeling_recurrent_gemma.py

@@ -915,13 +915,17 @@ def prepare_inputs_for_generation(
         if past_length > 0:
             position_ids = position_ids[:, past_length:]
 
-        if inputs_embeds is not None:
-            model_inputs = {"inputs_embeds": inputs_embeds[:, past_length:]}
+        if inputs_embeds is not None:  # Exception 1
+            input_ids = input_ids[:, -cache_position.shape[0] :]
+        elif input_ids.shape[1] != cache_position.shape[0]:  # Default case (the "else", a no op, is Exception 2)
+            input_ids = input_ids[:, cache_position]
+
+        # if `inputs_embeds` are passed, we only want to use them in the 1st generation step
+        if inputs_embeds is not None and cache_position[0] == 0:
+            model_inputs = {"inputs_embeds": inputs_embeds, "input_ids": None}
         else:
-            model_inputs = {"input_ids": input_ids[:, past_length:].contiguous()}
-
-        if cache_position is not None:
-            cache_position = cache_position[-position_ids.shape[1] :]
+            # The clone here is for the same reason as for `position_ids`.
+            model_inputs = {"input_ids": input_ids.clone(memory_format=torch.contiguous_format), "inputs_embeds": None}
 
         model_inputs.update(
             {