[Refactor]Base class for dit pipelines with unified parameter declaration[1/N] (#4225)

Signed-off-by: princepride <wangzhipeng628@gmail.com>
Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: Hongsheng Liu <liuhongsheng4@huawei.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

vllm_omni/diffusion/utils/param_utils.py

@@ -0,0 +1,27 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+from __future__ import annotations
+
+from vllm_omni.inputs.data import OmniDiffusionSamplingParams
+
+
+def apply_declared_extra_args(
+    sampling_params: OmniDiffusionSamplingParams,
+    declared_params: frozenset[str],
+    user_kwargs: dict[str, object],
+) -> None:
+    """Route pipeline-declared request params into ``sampling_params.extra_args``.
+
+    Both online serving and offline examples call this so that model-specific
+    keys (e.g. ``cfg_text_scale`` for BAGEL) end up in ``extra_args`` instead
+    of being silently dropped.
+
+    This is a no-op when no declared params are present in ``user_kwargs``, so
+    it is safe to call on non-diffusion (e.g. AR) sampling params whose
+    ``extra_args`` defaults to ``None``.
+    """
+    declared = {key: user_kwargs[key] for key in declared_params if user_kwargs.get(key) is not None}
+    if not declared:
+        return
+    sampling_params.extra_args = {**(sampling_params.extra_args or {}), **declared}