fix: tiny fix cli (#12744)

python/sglang/cli/serve.py

@@ -4,16 +4,49 @@ import argparse
 import logging
 import os
 
-from sglang.cli.main import get_is_diffusion_model, get_model_path
+from sglang.cli.utils import get_is_diffusion_model, get_model_path
 from sglang.srt.utils import kill_process_tree
 
 logger = logging.getLogger(__name__)
 
 
 def serve(args, extra_argv):
+    if any(h in extra_argv for h in ("-h", "--help")):
+        # Since the server type is determined by the model, and we don't have a model path,
+        # we can't show the exact help. Instead, we show a general help message and then
+        # the help for both possible server types.
+        print(
+            "Usage: sglang serve --model-path <model-name-or-path> [additional-arguments]\n"
+        )
+        print(
+            "This command can launch either a standard language model server or a diffusion model server."
+        )
+        print("The server type is determined by the model path.\n")
+        print("For specific arguments, please provide a model_path.")
+        print("\n--- Help for Standard Language Model Server ---")
+        from sglang.srt.server_args import prepare_server_args
+
+        try:
+            prepare_server_args(["--help"])
+        except SystemExit:
+            pass  # argparse --help calls sys.exit
+
+        print("\n--- Help for Diffusion Model Server ---")
+        from sglang.multimodal_gen.runtime.entrypoints.cli.serve import (
+            add_multimodal_gen_serve_args,
+        )
+
+        parser = argparse.ArgumentParser(description="SGLang Diffusion Model Serving")
+        add_multimodal_gen_serve_args(parser)
+        parser.print_help()
+        return
+
     model_path = get_model_path(extra_argv)
     try:
         is_diffusion_model = get_is_diffusion_model(model_path)
+        if is_diffusion_model:
+            logger.info("Diffusion model detected")
+
         if is_diffusion_model:
             # Logic for Diffusion Models
             from sglang.multimodal_gen.runtime.entrypoints.cli.serve import (