Fix local load for Medusa (#1420)

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Close #1418 
Close #1415

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server/text_generation_server/cli.py

@@ -198,6 +198,35 @@ def download_weights(
             if not extension == ".safetensors" or not auto_convert:
                 raise e
 
+    elif (Path(model_id) / "medusa_lm_head.pt").exists():
+        # Try to load as a local Medusa model
+        try:
+            import json
+
+            medusa_head = Path(model_id) / "medusa_lm_head.pt"
+            if auto_convert:
+                medusa_sf = Path(model_id) / "medusa_lm_head.safetensors"
+                if not medusa_sf.exists():
+                    utils.convert_files([Path(medusa_head)], [medusa_sf], [])
+            medusa_config = Path(model_id) / "config.json"
+            with open(medusa_config, "r") as f:
+                config = json.load(f)
+
+            model_id = config["base_model_name_or_path"]
+            revision = "main"
+            try:
+                utils.weight_files(model_id, revision, extension)
+                logger.info(
+                    f"Files for parent {model_id} are already present on the host. "
+                    "Skipping download."
+                )
+                return
+            # Local files not found
+            except (utils.LocalEntryNotFoundError, utils.EntryNotFoundError):
+                pass
+        except (utils.LocalEntryNotFoundError, utils.EntryNotFoundError):
+            pass
+            
     elif (Path(model_id) / "adapter_config.json").exists():
         # Try to load as a local PEFT model
         try:

server/text_generation_server/models/flash_llama.py

@@ -71,15 +71,26 @@ class FlashLlama(FlashCausalLM):
             from text_generation_server.utils.medusa import MedusaModel
             from huggingface_hub import hf_hub_download
             import json
+            import os
+            from pathlib import Path
             
+            is_local_model = (Path(use_medusa).exists() and Path(use_medusa).is_dir()) or os.getenv(
+                "WEIGHTS_CACHE_OVERRIDE", None
+            ) is not None
+            
+            if not is_local_model:
                 medusa_config = hf_hub_download(
                     use_medusa, revision=revision, filename="config.json"
                 )
-            with open(medusa_config, "r") as f:
-                config = json.load(f)
                 medusa_head = hf_hub_download(
                     use_medusa, revision=revision, filename="medusa_lm_head.pt"
                 )
+            else:
+                medusa_config = str(Path(use_medusa) / "config.json")
+                medusa_head = str(Path(use_medusa) / "medusa_lm_head.pt")
+                
+            with open(medusa_config, "r") as f:
+                config = json.load(f)
             medusa_sf = medusa_head[: -len(".pt")] + ".safetensors"
             weights = Weights(
                 [medusa_sf], device, dtype, process_group=self.process_group