[Diffusion] Add Minimax-H3 modular pipeline support (#5720)

Signed-off-by: Isotr0py <Isotr0py@outlook.com>
Signed-off-by: lishunyang12 <lishunyang12@163.com>
Signed-off-by: David Chen <530634352@qq.com>
Co-authored-by: lishunyang12 <lishunyang12@163.com>
Co-authored-by: SYLAR <125541396+lishunyang12@users.noreply.github.com>
Co-authored-by: David Chen <530634352@qq.com>

vllm_omni/diffusion/utils/hf_utils.py

@@ -7,6 +7,24 @@ from vllm.transformers_utils.config import get_hf_file_to_dict
 
 logger = init_logger(__name__)
 
+DIFFUSION_MODEL_INDEX_FILES = (
+    "model_index.json",
+    "modular_model_index.json",
+)
+
+
+def get_diffusion_model_index(
+    model_name: str,
+    *,
+    revision: str | None = None,
+) -> dict | None:
+    """Read the first standard Diffusers pipeline index available."""
+    for filename in DIFFUSION_MODEL_INDEX_FILES:
+        config = get_hf_file_to_dict(filename, model_name, revision=revision)
+        if isinstance(config, Mapping):
+            return dict(config)
+    return None
+
 
 def load_diffusers_config(model_name) -> dict:
     from diffusers.pipelines.pipeline_utils import DiffusionPipeline
@@ -58,33 +76,32 @@ 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)
+    1. Check the local file system for a standard Diffusers index
     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):
+        for filename in DIFFUSION_MODEL_INDEX_FILES:
+            model_index_path = os.path.join(model_name, filename)
+            if not os.path.exists(model_index_path):
+                continue
             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")
+                    logger.debug("Detected diffusion model via local %s", filename)
                     return True
             except Exception as e:
-                logger.debug("Failed to read local model_index.json: %s", e)
+                logger.debug("Failed to read local %s: %s", filename, e)
 
     # Strategy 2: Check using vllm's utility (works for both local and remote models)
-    try:
-        config_dict = get_hf_file_to_dict("model_index.json", model_name)
-        if config_dict is not None and 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)
+    config_dict = get_diffusion_model_index(model_name)
+    if config_dict is not None and config_dict.get("_class_name") and config_dict.get("_diffusers_version"):
+        logger.debug("Detected diffusion model via a standard Diffusers index")
+        return True
 
     # Strategy 3: Try the standard diffusers approach (may fail due to import issues)
     # This is last because it requires importing diffusers/xformers/flash_attn