Generate: check that attention_mask is 2D (huggingface#33575)

check attention mask in generate

src/transformers/generation/utils.py

@@ -1864,6 +1864,10 @@ def generate(
             model_kwargs["attention_mask"] = self._prepare_attention_mask_for_generation(
                 inputs_tensor, generation_config._pad_token_tensor, generation_config._eos_token_tensor
             )
+        elif kwargs_has_attention_mask:
+            # TODO (joao): generalize this check with other types of inputs
+            if model_input_name == "input_ids" and len(model_kwargs["attention_mask"].shape) > 2:
+                raise ValueError("`attention_mask` passed to `generate` must be 2D.")
 
         if self.config.is_encoder_decoder and "encoder_outputs" not in model_kwargs:
             # if model is encoder decoder encoder_outputs are created and added to `model_kwargs`