[New model] Support model qwen image layered (#381)

Signed-off-by: dengyunyang <584797741@qq.com>

vllm_omni/diffusion/utils/hf_utils.py

@@ -1,6 +1,8 @@
+import os
 from functools import lru_cache
 
 from vllm.logger import init_logger
+from vllm.transformers_utils.config import get_hf_file_to_dict
 
 logger = init_logger(__name__)
 
@@ -14,8 +16,49 @@ def load_diffusers_config(model_name) -> dict:
 
 @lru_cache
 def is_diffusion_model(model_name: str) -> bool:
+    """Check if a model is a diffusion model.
+
+    Uses multiple fallback strategies to detect diffusion models:
+    1. Check local file system for model_index.json (fastest, no imports)
+    2. Check using vllm's get_hf_file_to_dict utility
+    3. Try the standard diffusers approach (may fail due to import issues)
+    """
+    # Strategy 1: Check local file system first (fastest, avoids import issues)
+    if os.path.isdir(model_name):
+        model_index_path = os.path.join(model_name, "model_index.json")
+        if os.path.exists(model_index_path):
+            try:
+                import json
+
+                with open(model_index_path) as f:
+                    config_dict = json.load(f)
+                if config_dict.get("_class_name") and config_dict.get("_diffusers_version"):
+                    logger.debug("Detected diffusion model via local model_index.json")
+                    return True
+            except Exception as e:
+                logger.debug("Failed to read local model_index.json: %s", e)
+
+    # Strategy 2: Check using vllm's utility (works for both local and remote models)
+    try:
+        # Try to get model_index.json using vllm's utility
+        config_dict = get_hf_file_to_dict("model_index.json", model_name)
+        # Verify it has the required fields for a diffusers model
+        if config_dict.get("_class_name") and config_dict.get("_diffusers_version"):
+            logger.debug("Detected diffusion model via model_index.json")
+            return True
+    except Exception as e:
+        logger.debug("Failed to check model_index.json via get_hf_file_to_dict: %s", e)
+
+    # Strategy 3: Try the standard diffusers approach (may fail due to import issues)
+    # This is last because it requires importing diffusers/xformers/flash_attn
+    # which may have compatibility issues
     try:
         load_diffusers_config(model_name)
         return True
-    except Exception:
-        return False
+    except (ImportError, ModuleNotFoundError) as e:
+        logger.debug("Failed to import diffusers dependencies: %s", e)
+        logger.debug("This may be due to flash_attn/PyTorch version mismatch")
+    except Exception as e:
+        logger.debug("Failed to load diffusers config via DiffusionPipeline: %s", e)
+
+    return False