Fix issue with Literal and Optional cli arguments not working. Closes #702

llama_cpp/server/__main__.py

@@ -23,11 +23,27 @@ Then visit http://localhost:8000/docs to see the interactive API docs.
 """
 import os
 import argparse
+from typing import Literal, Union
 
 import uvicorn
 
 from llama_cpp.server.app import create_app, Settings
 
+def get_non_none_base_types(annotation):
+    if not hasattr(annotation, "__args__"):
+        return annotation
+    return [arg for arg in annotation.__args__ if arg is not type(None)][0]
+
+def get_base_type(annotation):
+    if getattr(annotation, '__origin__', None) is Literal:
+        return type(annotation.__args__[0])
+    elif getattr(annotation, '__origin__', None) is Union:
+        non_optional_args = [arg for arg in annotation.__args__ if arg is not type(None)]
+        if non_optional_args:
+            return get_base_type(non_optional_args[0])
+    else:
+        return annotation
+
 if __name__ == "__main__":
     parser = argparse.ArgumentParser()
     for name, field in Settings.model_fields.items():
@@ -37,7 +53,7 @@ if __name__ == "__main__":
         parser.add_argument(
             f"--{name}",
             dest=name,
-            type=field.annotation if field.annotation is not None else str,
+            type=get_base_type(field.annotation) if field.annotation is not None else str,
             help=description,
         )