Migrate all ServerArgs fields to Annotated style, reduce add_cli_args by ~2400 lines (#28919)

python/sglang/srt/arg_groups/arg_utils.py

@@ -70,6 +70,7 @@ class Arg:
     required: Optional[bool] = None
     action: Optional[Any] = None
     action_kwargs: Optional[dict] = None
+    const: Optional[Any] = None
     # When True, this field is skipped by add_cli_args_from_dataclass.
     # Use for fields that have no CLI surface (e.g. injected via Python only).
     no_cli: bool = False
@@ -185,12 +186,18 @@ def add_cli_args_from_dataclass(parser, cls, *, fields: Optional[List[str]] = No
         cli_name = arg_meta.cli_name or _field_to_cli_name(field.name)
         names = [cli_name] + (arg_meta.aliases or [])
         default = _field_default(field)
+        # Anchor dest to the field name so argparse stores the value
+        # under the dataclass attribute directly, even when cli_name
+        # differs (e.g. --tensor-parallel-size → tp_size).
+        auto_dest = cli_name.lstrip("-").replace("-", "_")
+        dest_kwarg = {"dest": field.name} if field.name != auto_dest else {}
 
         # Handle custom action
         if arg_meta.action is not None:
             kwargs = {
                 "action": arg_meta.action,
                 "help": arg_meta.help,
+                **dest_kwarg,
             }
             if default is not _MISSING:
                 kwargs["default"] = default
@@ -209,34 +216,42 @@ def add_cli_args_from_dataclass(parser, cls, *, fields: Optional[List[str]] = No
             # Infer type from first literal value
             val_type = type(literal_vals[0]) if literal_vals else str
             type_func = arg_meta.type_parser or _infer_type_func(val_type)
-            kwargs = dict(type=type_func, choices=choices, help=arg_meta.help)
+            kwargs = dict(
+                type=type_func, choices=choices, help=arg_meta.help, **dest_kwarg
+            )
             if default is not _MISSING:
                 kwargs["default"] = default
+            if arg_meta.const is not None:
+                kwargs["const"] = arg_meta.const
             parser.add_argument(*names, **kwargs)
             continue
 
-        # Check for List[X]
+        # Check for List[X] — but skip if type_parser is set (the parser
+        # handles the whole value as a single string, e.g. json_list_type).
         origin = get_origin(inner_type)
-        if origin is list or origin is List:
+        if (origin is list or origin is List) and arg_meta.type_parser is None:
             elem_args = get_args(inner_type)
             elem_type = elem_args[0] if elem_args else str
-            type_func = arg_meta.type_parser or _infer_type_func(elem_type)
+            type_func = _infer_type_func(elem_type)
             nargs = arg_meta.nargs or "+"
             kwargs = dict(
                 type=type_func,
                 nargs=nargs,
                 help=arg_meta.help,
+                **dest_kwarg,
             )
             if arg_meta.choices:
                 kwargs["choices"] = arg_meta.choices
             if default is not _MISSING:
                 kwargs["default"] = default
+            if arg_meta.const is not None:
+                kwargs["const"] = arg_meta.const
             parser.add_argument(*names, **kwargs)
             continue
 
         # Bool → store_true
         if inner_type is bool:
-            kwargs = dict(action="store_true", help=arg_meta.help)
+            kwargs = dict(action="store_true", help=arg_meta.help, **dest_kwarg)
             if default is not _MISSING:
                 kwargs["default"] = default
             parser.add_argument(*names, **kwargs)
@@ -244,13 +259,15 @@ def add_cli_args_from_dataclass(parser, cls, *, fields: Optional[List[str]] = No
 
         # Scalar types (str, int, float, etc.)
         type_func = arg_meta.type_parser or _infer_type_func(inner_type)
-        kwargs = dict(type=type_func, help=arg_meta.help)
+        kwargs = dict(type=type_func, help=arg_meta.help, **dest_kwarg)
         if arg_meta.choices:
             kwargs["choices"] = arg_meta.choices
         if arg_meta.nargs:
             kwargs["nargs"] = arg_meta.nargs
         if default is not _MISSING:
             kwargs["default"] = default
+        if arg_meta.const is not None:
+            kwargs["const"] = arg_meta.const
         if (
             arg_meta.required is True
             or (arg_meta.required is None and default is _MISSING)