[Feature] Use pydantic validation in lora.py and load.py configs (#26413)

Signed-off-by: simondanielsson <simon.danielsson99@hotmail.com>

vllm/config/load.py

@@ -2,9 +2,9 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
 import hashlib
-from dataclasses import field
 from typing import TYPE_CHECKING, Any, Optional, Union
 
+from pydantic import Field, field_validator
 from pydantic.dataclasses import dataclass
 
 from vllm.config.utils import config
@@ -64,7 +64,7 @@ class LoadConfig:
       was quantized using torchao and saved using safetensors.
       Needs torchao >= 0.14.0
     """
-    model_loader_extra_config: Union[dict, TensorizerConfig] = field(
+    model_loader_extra_config: Union[dict, TensorizerConfig] = Field(
         default_factory=dict
     )
     """Extra config for model loader. This will be passed to the model loader
@@ -72,7 +72,9 @@ class LoadConfig:
     device: Optional[str] = None
     """Device to which model weights will be loaded, default to
     device_config.device"""
-    ignore_patterns: Optional[Union[list[str], str]] = None
+    ignore_patterns: Union[list[str], str] = Field(
+        default_factory=lambda: ["original/**/*"]
+    )
     """The list of patterns to ignore when loading the model. Default to
     "original/**/*" to avoid repeated loading of llama's checkpoints."""
     use_tqdm_on_load: bool = True
@@ -107,12 +109,18 @@ class LoadConfig:
         hash_str = hashlib.md5(str(factors).encode(), usedforsecurity=False).hexdigest()
         return hash_str
 
-    def __post_init__(self):
-        self.load_format = self.load_format.lower()
-        if self.ignore_patterns is not None and len(self.ignore_patterns) > 0:
+    @field_validator("load_format", mode="after")
+    def _lowercase_load_format(cls, load_format: str) -> str:
+        return load_format.lower()
+
+    @field_validator("ignore_patterns", mode="after")
+    def _validate_ignore_patterns(
+        cls, ignore_patterns: Union[list[str], str]
+    ) -> Union[list[str], str]:
+        if ignore_patterns != ["original/**/*"] and len(ignore_patterns) > 0:
             logger.info(
                 "Ignoring the following patterns when downloading weights: %s",
-                self.ignore_patterns,
+                ignore_patterns,
             )
-        else:
-            self.ignore_patterns = ["original/**/*"]
+
+        return ignore_patterns