chore: Initial support for input config files (#10534)

Co-authored-by: root <root@umbriel-b200-017.ipp4a1.colossus.nvidia.com>
Co-authored-by: Yineng Zhang <me@zhyncs.com>

python/sglang/srt/server_args.py

@@ -2659,6 +2659,13 @@ class ServerArgs:
             help="NOTE: --enable-flashinfer-mxfp4-moe is deprecated. Please set `--moe-runner-backend` to 'flashinfer_mxfp4' instead.",
         )
 
+        # Configuration file support
+        parser.add_argument(
+            "--config",
+            type=str,
+            help="Read CLI options from a config file. Must be a YAML file with configuration options.",
+        )
+
     @classmethod
     def from_cli_args(cls, args: argparse.Namespace):
         args.tp_size = args.tensor_parallel_size
@@ -2939,6 +2946,26 @@ def prepare_server_args(argv: List[str]) -> ServerArgs:
     Returns:
         The server arguments.
     """
+    # Import here to avoid circular imports
+    from sglang.srt.server_args_config_parser import ConfigArgumentMerger
+
+    # Check for config file and merge arguments if present
+    if "--config" in argv:
+        # Extract boolean actions from the parser to handle them correctly
+        parser = argparse.ArgumentParser()
+        ServerArgs.add_cli_args(parser)
+
+        # Get boolean action destinations
+        boolean_actions = []
+        for action in parser._actions:
+            if hasattr(action, "dest") and hasattr(action, "action"):
+                if action.action in ["store_true", "store_false"]:
+                    boolean_actions.append(action.dest)
+
+        # Merge config file arguments with CLI arguments
+        config_merger = ConfigArgumentMerger(boolean_actions=boolean_actions)
+        argv = config_merger.merge_config_with_args(argv)
+
     parser = argparse.ArgumentParser()
     ServerArgs.add_cli_args(parser)
     raw_args = parser.parse_args(argv)

python/sglang/srt/server_args_config_parser.py

@@ -0,0 +1,146 @@
+"""
+Configuration argument parser for command-line applications.
+Handles merging of YAML configuration files with command-line arguments.
+"""
+
+import logging
+from pathlib import Path
+from typing import Any, Dict, List, Union
+
+import yaml
+
+logger = logging.getLogger(__name__)
+
+
+class ConfigArgumentMerger:
+    """Handles merging of configuration file arguments with command-line arguments."""
+
+    def __init__(self, boolean_actions: List[str] = None):
+        """Initialize with list of boolean action destinations."""
+        self.boolean_actions = boolean_actions or []
+
+    def merge_config_with_args(self, cli_args: List[str]) -> List[str]:
+        """
+        Merge configuration file arguments with command-line arguments.
+
+        Configuration arguments are inserted after the subcommand to maintain
+        proper precedence: CLI > Config > Defaults
+
+        Args:
+            cli_args: List of command-line arguments
+
+        Returns:
+            Merged argument list with config values inserted
+
+        Raises:
+            ValueError: If multiple config files specified or no config file provided
+        """
+        config_file_path = self._extract_config_file_path(cli_args)
+        if not config_file_path:
+            return cli_args
+
+        config_args = self._parse_yaml_config(config_file_path)
+        return self._insert_config_args(cli_args, config_args, config_file_path)
+
+    def _extract_config_file_path(self, args: List[str]) -> str:
+        """Extract the config file path from arguments."""
+        config_indices = [i for i, arg in enumerate(args) if arg == "--config"]
+
+        if len(config_indices) > 1:
+            raise ValueError("Multiple config files specified! Only one allowed.")
+
+        if not config_indices:
+            return None
+
+        config_index = config_indices[0]
+        if config_index == len(args) - 1:
+            raise ValueError("No config file specified after --config flag!")
+
+        return args[config_index + 1]
+
+    def _insert_config_args(
+        self, cli_args: List[str], config_args: List[str], config_file_path: str
+    ) -> List[str]:
+        """Insert configuration arguments into the CLI argument list."""
+        config_index = cli_args.index("--config")
+
+        # Split arguments around config file
+        before_config = cli_args[:config_index]
+        after_config = cli_args[config_index + 2 :]  # Skip --config and file path
+
+        # Simple merge: config args + CLI args
+        return config_args + before_config + after_config
+
+    def _parse_yaml_config(self, file_path: str) -> List[str]:
+        """
+        Parse YAML configuration file and convert to argument list.
+
+        Args:
+            file_path: Path to the YAML configuration file
+
+        Returns:
+            List of arguments in format ['--key', 'value', ...]
+
+        Raises:
+            ValueError: If file is not YAML or cannot be read
+        """
+        self._validate_yaml_file(file_path)
+
+        try:
+            with open(file_path, "r") as file:
+                config_data = yaml.safe_load(file)
+        except Exception as e:
+            logger.error(f"Failed to read config file {file_path}: {e}")
+            raise
+
+        # Handle empty files or None content
+        if config_data is None:
+            config_data = {}
+
+        if not isinstance(config_data, dict):
+            raise ValueError("Config file must contain a dictionary at root level")
+
+        return self._convert_config_to_args(config_data)
+
+    def _validate_yaml_file(self, file_path: str) -> None:
+        """Validate that the file is a YAML file."""
+        path = Path(file_path)
+        if path.suffix.lower() not in [".yaml", ".yml"]:
+            raise ValueError(f"Config file must be YAML format, got: {path.suffix}")
+
+        if not path.exists():
+            raise ValueError(f"Config file not found: {file_path}")
+
+    def _convert_config_to_args(self, config: Dict[str, Any]) -> List[str]:
+        """Convert configuration dictionary to argument list."""
+        args = []
+
+        for key, value in config.items():
+            if isinstance(value, bool):
+                self._add_boolean_arg(args, key, value)
+            elif isinstance(value, list):
+                self._add_list_arg(args, key, value)
+            else:
+                self._add_scalar_arg(args, key, value)
+
+        return args
+
+    def _add_boolean_arg(self, args: List[str], key: str, value: bool) -> None:
+        """Add boolean argument to the list."""
+        if key in self.boolean_actions:
+            # For boolean actions, always add the flag and value
+            args.extend([f"--{key}", str(value).lower()])
+        else:
+            # For regular booleans, only add flag if True
+            if value:
+                args.append(f"--{key}")
+
+    def _add_list_arg(self, args: List[str], key: str, value: List[Any]) -> None:
+        """Add list argument to the list."""
+        if value:  # Only add if list is not empty
+            args.append(f"--{key}")
+            args.extend(str(item) for item in value)
+
+    def _add_scalar_arg(self, args: List[str], key: str, value: Any) -> None:
+        """Add scalar argument to the list."""
+        args.extend([f"--{key}", str(value)])