[DataFlow runtime 1/7] Make SGLang target imports optional

specforge/modeling/target/eagle3_target_model.py

@@ -3,41 +3,65 @@
 from dataclasses import dataclass
 from typing import List, Optional, Tuple
 
-import sglang.srt.managers.mm_utils as mm_utils
 import torch
 import torch.distributed as dist
 import torch.nn as nn
-from sglang.srt.configs.model_config import ModelConfig
-from sglang.srt.layers.rotary_embedding import MRotaryEmbedding
-from sglang.srt.managers.mm_utils import (
-    MultiModalityDataPaddingPatternMultimodalTokens,
-    init_mm_embedding_cache,
-)
-from sglang.srt.managers.schedule_batch import (
-    Modality,
-    MultimodalDataItem,
-    MultimodalInputs,
-    Req,
-    ScheduleBatch,
-)
-
-# - prepare_mlp_sync_batch_raw is now a module-level function, not a Scheduler method
-from sglang.srt.managers.scheduler_dp_attn_mixin import prepare_mlp_sync_batch_raw
-from sglang.srt.mem_cache.cache_init_params import CacheInitParams
-from sglang.srt.mem_cache.radix_cache import RadixCache
-from sglang.srt.model_executor.forward_batch_info import CaptureHiddenMode, ForwardBatch
-from sglang.srt.multimodal.processors.base_processor import BaseMultimodalProcessor
-from sglang.srt.sampling.sampling_params import SamplingParams
-from sglang.srt.server_args import ServerArgs
-from sglang.srt.speculative.spec_info import SpeculativeAlgorithm
-from sglang.srt.utils import require_mlp_sync, require_mlp_tp_gather
 from transformers import AutoModelForCausalLM
 
 from specforge.distributed import get_tp_device_mesh, get_tp_group
 from specforge.utils import padding
 
-from .sglang_backend import SGLangRunner, wrap_eagle3_logits_processors_in_module
-from .sglang_backend.utils import LogitsProcessorForEAGLE3
+# SGLang internals back the *sglang* target backend only. Keep these imports
+# optional so `import specforge` (and the HF / offline / draft paths) still works
+# when the installed sglang version does not expose the exact symbols this file
+# pins. The SGLang backend then surfaces a clear error at construction time
+# (see SGLangEagle3TargetModel.from_pretrained). This keeps the engine behind a
+# replaceable boundary rather than a hard, version-locked import dependency.
+try:
+    import sglang.srt.managers.mm_utils as mm_utils
+    from sglang.srt.configs.model_config import ModelConfig
+    from sglang.srt.layers.rotary_embedding import MRotaryEmbedding
+    from sglang.srt.managers.mm_utils import (
+        MultiModalityDataPaddingPatternMultimodalTokens,
+        init_mm_embedding_cache,
+    )
+    from sglang.srt.managers.schedule_batch import (
+        Modality,
+        MultimodalDataItem,
+        MultimodalInputs,
+        Req,
+        ScheduleBatch,
+    )
+
+    # prepare_mlp_sync_batch_raw is a module-level function, not a Scheduler method
+    from sglang.srt.managers.scheduler_dp_attn_mixin import prepare_mlp_sync_batch_raw
+    from sglang.srt.mem_cache.cache_init_params import CacheInitParams
+    from sglang.srt.mem_cache.radix_cache import RadixCache
+    from sglang.srt.model_executor.forward_batch_info import (
+        CaptureHiddenMode,
+        ForwardBatch,
+    )
+    from sglang.srt.multimodal.processors.base_processor import BaseMultimodalProcessor
+    from sglang.srt.sampling.sampling_params import SamplingParams
+    from sglang.srt.server_args import ServerArgs
+    from sglang.srt.speculative.spec_info import SpeculativeAlgorithm
+    from sglang.srt.utils import require_mlp_sync, require_mlp_tp_gather
+
+    from .sglang_backend import SGLangRunner, wrap_eagle3_logits_processors_in_module
+    from .sglang_backend.utils import LogitsProcessorForEAGLE3
+
+    _SGLANG_IMPORT_ERROR = None
+except Exception as _exc:  # pragma: no cover - depends on installed sglang version
+    _SGLANG_IMPORT_ERROR = _exc
+    mm_utils = ModelConfig = MRotaryEmbedding = None
+    MultiModalityDataPaddingPatternMultimodalTokens = init_mm_embedding_cache = None
+    Modality = MultimodalDataItem = MultimodalInputs = Req = ScheduleBatch = None
+    prepare_mlp_sync_batch_raw = CacheInitParams = RadixCache = None
+    CaptureHiddenMode = ForwardBatch = BaseMultimodalProcessor = None
+    SamplingParams = ServerArgs = SpeculativeAlgorithm = None
+    require_mlp_sync = require_mlp_tp_gather = None
+    SGLangRunner = wrap_eagle3_logits_processors_in_module = None
+    LogitsProcessorForEAGLE3 = None
 
 logger = logging.getLogger(__name__)