[Core] Add update_config RPC method (#20095)

Signed-off-by: 22quinn <33176974+22quinn@users.noreply.github.com>

vllm/config.py

@@ -71,6 +71,7 @@ if TYPE_CHECKING:
     ConfigType = type[DataclassInstance]
     HfOverrides = Union[dict, Callable[[type], type]]
 else:
+    DataclassInstance = Any
     PlacementGroup = Any
     PretrainedConfig = Any
     ExecutorBase = Any
@@ -87,7 +88,7 @@ else:
                            "vllm.model_executor.models")
 
 logger = init_logger(__name__)
-
+DataclassInstanceT = TypeVar("DataclassInstanceT", bound=DataclassInstance)
 ConfigT = TypeVar("ConfigT", bound=ConfigType)
 
 TaskOption = Literal["auto", "generate", "embedding", "embed", "classify",
@@ -5049,3 +5050,21 @@ class SpeechToTextConfig:
     @property
     def allow_audio_chunking(self) -> bool:
         return self.min_energy_split_window_size is not None
+
+
+def update_config(config: DataclassInstanceT,
+                  overrides: dict[str, Any]) -> DataclassInstanceT:
+    processed_overrides = {}
+    for field_name, value in overrides.items():
+        assert hasattr(
+            config, field_name), f"{type(config)} has no field `{field_name}`"
+        current_value = getattr(config, field_name)
+        if is_dataclass(current_value) and not is_dataclass(value):
+            assert isinstance(value, dict), (
+                f"Overrides to {type(config)}.{field_name} must be a dict"
+                f"  or {type(current_value)}, but got {type(value)}")
+            value = update_config(
+                current_value,  # type: ignore[type-var]
+                value)
+        processed_overrides[field_name] = value
+    return replace(config, **processed_overrides)