[Misc] Make `LayerBlockType` a `Literal` instead of `Enum` (#27658)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

vllm/config/model.py

@@ -41,7 +41,6 @@ from vllm.transformers_utils.config import (
 )
 from vllm.transformers_utils.runai_utils import ObjectStorageModel, is_runai_obj_uri
 from vllm.transformers_utils.utils import maybe_model_redirect
-from vllm.utils import LayerBlockType
 from vllm.utils.import_utils import LazyLoader
 from vllm.utils.torch_utils import common_broadcastable_dtype
 
@@ -91,6 +90,7 @@ LogprobsMode = Literal[
 ]
 HfOverrides = dict[str, Any] | Callable[[PretrainedConfig], PretrainedConfig]
 ModelImpl = Literal["auto", "vllm", "transformers", "terratorch"]
+LayerBlockType = Literal["attention", "linear_attention", "mamba"]
 
 _RUNNER_TASKS: dict[RunnerType, list[TaskOption]] = {
     "generate": ["generate", "transcription"],
@@ -1433,11 +1433,11 @@ class ModelConfig:
     def get_num_layers_by_block_type(
         self,
         parallel_config: ParallelConfig,
-        block_type: LayerBlockType = LayerBlockType.attention,
+        block_type: LayerBlockType = "attention",
     ) -> int:
         # This function relies on 'layers_block_type' in hf_config,
         # for w/o this attribute, we will need to have workarounds like so
-        attn_block_type = block_type == LayerBlockType.attention
+        attn_block_type = block_type == "attention"
         is_transformer = (
             not self.is_hybrid and not self.has_noops and not self.is_attention_free
         )
@@ -1469,9 +1469,7 @@ class ModelConfig:
                         )
                     else:
                         return self.get_num_layers(parallel_config)
-                return sum(
-                    t == block_type.value for t in layers_block_type_value[start:end]
-                )
+                return sum(t == block_type for t in layers_block_type_value[start:end])
 
             # Hybrid model Minimax
             attn_type_list = getattr(self.hf_config, "attn_type_list", None)
@@ -1481,19 +1479,16 @@ class ModelConfig:
             # Hybrid model Qwen3Next
             layer_types_value = getattr(self.hf_config, "layer_types", None)
             if layer_types_value is not None:
-                if getattr(block_type, "value", block_type) == "attention":
+                if block_type == "attention":
                     return sum(
                         t == "full_attention" for t in layer_types_value[start:end]
                     )
-                elif getattr(block_type, "value", block_type) == "linear_attention":
+                elif block_type == "linear_attention":
                     return sum(
                         t == "linear_attention" for t in layer_types_value[start:end]
                     )
                 else:
-                    return sum(
-                        t == getattr(block_type, "value", block_type)
-                        for t in layer_types_value[start:end]
-                    )
+                    return sum(t == block_type for t in layer_types_value[start:end])
 
             if (
                 layers_block_type_value is None
@@ -1501,10 +1496,9 @@ class ModelConfig:
                 and layer_types_value is None
             ):
                 raise ValueError(
-                    "The model is an hybrid without a"
-                    "layers_block_type or an attn_type_list, or a layer_types "
-                    "in the hf_config, cannot determine the num of "
-                    f"{block_type.value} layers"
+                    "The model is an hybrid without a layers_block_type or an "
+                    "attn_type_list, or a layer_types in the hf_config, "
+                    f"cannot determine the num of {block_type} layers"
                 )
 
     def get_mamba_chunk_size(self) -> int | None:

vllm/utils/__init__.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
-import enum
 import inspect
 import uuid
 import warnings
@@ -67,11 +66,6 @@ STR_INVALID_VAL: str = "INVALID"
 T = TypeVar("T")
 
 
-class LayerBlockType(enum.Enum):
-    attention = "attention"
-    mamba = "mamba"
-
-
 def random_uuid() -> str:
     return str(uuid.uuid4().hex)
 

vllm/v1/worker/tpu_model_runner.py

@@ -53,7 +53,6 @@ from vllm.multimodal.inputs import (
 from vllm.multimodal.utils import group_mm_kwargs_by_modality
 from vllm.sequence import IntermediateTensors
 from vllm.tasks import GenerationTask, PoolingTask, SupportedTask
-from vllm.utils import LayerBlockType
 from vllm.utils.math_utils import cdiv, prev_power_of_2
 from vllm.utils.platform_utils import is_pin_memory_available
 from vllm.v1.attention.backends.pallas import (
@@ -212,7 +211,7 @@ class TPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
 
         # Model-related.
         self.num_attn_layers = model_config.get_num_layers_by_block_type(
-            parallel_config, LayerBlockType.attention
+            parallel_config, "attention"
         )
         self.num_query_heads = model_config.get_num_attention_heads(parallel_config)
         self.num_kv_heads = model_config.get_num_kv_heads(parallel_config)