[Bugfix] Do not read falsy request values as unset in the API layer

tests/entrypoints/unit_tests/test_falsy_request_params.py

@@ -0,0 +1,94 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+"""Falsy-but-explicit request values must not be read as "field omitted".
+
+Each case below covers a request field typed ``X | None`` whose consumer used a
+truthiness test, so a caller-supplied falsy value took the branch reserved for
+an omitted field.
+
+This extends the falsy-field coverage of #48098 to the chat template and stream
+option paths.
+"""
+
+import pytest
+
+from vllm.entrypoints.openai.chat_completion.protocol import ChatCompletionRequest
+from vllm.entrypoints.openai.completion.protocol import CompletionRequest
+from vllm.entrypoints.pooling.embed.protocol import EmbeddingChatRequest
+from vllm.entrypoints.serve.tokenize.protocol import TokenizeChatRequest
+from vllm.exceptions import VLLMValidationError
+
+pytestmark = pytest.mark.skip_global_cleanup
+
+SERVER_TEMPLATE = "{{ 'server default' }}"
+
+CHAT_BODY = {"model": "qwen", "messages": [{"role": "user", "content": "hello"}]}
+
+CHAT_TEMPLATE_MODELS = [
+    ChatCompletionRequest,
+    TokenizeChatRequest,
+    EmbeddingChatRequest,
+]
+
+STREAM_OPTION_BODIES = [
+    (ChatCompletionRequest, CHAT_BODY),
+    (CompletionRequest, {"model": "qwen", "prompt": "hello"}),
+]
+IDS = [model.__name__ for model, _ in STREAM_OPTION_BODIES]
+
+
+@pytest.mark.parametrize(
+    "request_model", CHAT_TEMPLATE_MODELS, ids=lambda m: m.__name__
+)
+def test_empty_chat_template_is_not_replaced_by_the_server_default(request_model):
+    """``chat_template: ""`` must reach the renderer as the caller wrote it.
+
+    ``OnlineRenderer.validate_chat_template`` already counts ``""`` as a
+    caller-supplied template and refuses it unless
+    ``--trust-request-chat-template`` is set, so substituting the server
+    template afterwards renders a prompt the caller never asked for.
+    """
+    request = request_model.model_validate({**CHAT_BODY, "chat_template": ""})
+
+    chat_params = request.build_chat_params(SERVER_TEMPLATE, "auto")
+
+    assert chat_params.chat_template == ""
+
+
+@pytest.mark.parametrize(
+    "request_model", CHAT_TEMPLATE_MODELS, ids=lambda m: m.__name__
+)
+def test_omitted_chat_template_still_falls_back_to_the_server_default(request_model):
+    request = request_model.model_validate(dict(CHAT_BODY))
+
+    chat_params = request.build_chat_params(SERVER_TEMPLATE, "auto")
+
+    assert chat_params.chat_template == SERVER_TEMPLATE
+
+
+@pytest.mark.parametrize(("request_model", "body"), STREAM_OPTION_BODIES, ids=IDS)
+def test_empty_stream_options_are_refused_without_streaming(request_model, body):
+    """``stream_options: {}`` is still ``stream_options``.
+
+    The field is meaningless outside a streaming request, and an empty object
+    is no more meaningful there than a populated one.
+    """
+    with pytest.raises(VLLMValidationError, match="stream_options"):
+        request_model.model_validate({**body, "stream": False, "stream_options": {}})
+
+
+@pytest.mark.parametrize(("request_model", "body"), STREAM_OPTION_BODIES, ids=IDS)
+def test_empty_stream_options_are_accepted_with_streaming(request_model, body):
+    request = request_model.model_validate(
+        {**body, "stream": True, "stream_options": {}}
+    )
+
+    assert request.stream_options is not None
+
+
+@pytest.mark.parametrize(("request_model", "body"), STREAM_OPTION_BODIES, ids=IDS)
+def test_omitted_stream_options_are_accepted_without_streaming(request_model, body):
+    request = request_model.model_validate({**body, "stream": False})
+
+    assert request.stream_options is None

tests/renderers/test_tokenize_params.py

@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""``TokenizeParams.with_kwargs`` overrides that are spelled as ``False``.
+
+``padding`` and ``truncation`` accept the HuggingFace spellings documented at
+https://huggingface.co/docs/transformers/en/pad_truncation, where ``False`` and
+``"do_not_pad"`` / ``"do_not_truncate"`` mean the same thing. The two spellings
+must therefore produce the same ``TokenizeParams``.
+"""
+
+import pytest
+
+from vllm.renderers import TokenizeParams
+
+pytestmark = pytest.mark.skip_global_cleanup
+
+
+@pytest.fixture
+def params() -> TokenizeParams:
+    return TokenizeParams(
+        max_total_tokens=1024,
+        max_output_tokens=16,
+        pad_prompt_tokens=64,
+        truncate_prompt_tokens=128,
+    )
+
+
+@pytest.mark.parametrize("truncation", [False, "do_not_truncate"])
+def test_disabling_truncation_clears_truncate_prompt_tokens(params, truncation):
+    assert params.with_kwargs(truncation=truncation).truncate_prompt_tokens is None
+
+
+@pytest.mark.parametrize("padding", [False, "do_not_pad"])
+def test_disabling_padding_clears_pad_prompt_tokens(params, padding):
+    assert params.with_kwargs(padding=padding).pad_prompt_tokens is None
+
+
+def test_enabling_truncation_still_uses_the_input_budget(params):
+    child = params.with_kwargs(truncation=True)
+
+    assert child.truncate_prompt_tokens == params.max_input_tokens
+
+
+def test_padding_to_max_length_still_uses_the_input_budget(params):
+    child = params.with_kwargs(padding="max_length")
+
+    assert child.pad_prompt_tokens == params.max_input_tokens
+
+
+def test_omitting_the_overrides_preserves_the_parent_values(params):
+    child = params.with_kwargs(add_special_tokens=False)
+
+    assert child.truncate_prompt_tokens == 128
+    assert child.pad_prompt_tokens == 64

vllm/entrypoints/openai/chat_completion/protocol.py

@@ -588,7 +588,9 @@ def build_chat_params(
             extra_kwargs["enable_thinking"] = self.reasoning_effort != "none"
 
         return ChatParams(
-            chat_template=self.chat_template or default_template,
+            chat_template=(
+                default_template if self.chat_template is None else self.chat_template
+            ),
             chat_template_content_format=default_template_content_format,
             chat_template_kwargs=merge_kwargs(
                 self.chat_template_kwargs,
@@ -787,7 +789,7 @@ def validate_response_format(cls, data):
     def validate_stream_options(cls, data):
         if not isinstance(data, dict):
             return data
-        if data.get("stream_options") and not data.get("stream"):
+        if data.get("stream_options") is not None and not data.get("stream"):
             raise VLLMValidationError(
                 "Stream options can only be defined when `stream=True`.",
                 parameter="stream_options",

vllm/entrypoints/openai/completion/protocol.py

@@ -544,7 +544,7 @@ def check_logprobs(cls, data):
     def validate_stream_options(cls, data):
         if not isinstance(data, dict):
             return data
-        if data.get("stream_options") and not data.get("stream"):
+        if data.get("stream_options") is not None and not data.get("stream"):
             raise VLLMValidationError(
                 "Stream options can only be defined when `stream=True`.",
                 parameter="stream_options",

vllm/entrypoints/pooling/base/protocol.py

@@ -254,7 +254,9 @@ def build_chat_params(
         default_template_content_format: ChatTemplateContentFormatOption,
     ) -> ChatParams:
         return ChatParams(
-            chat_template=self.chat_template or default_template,
+            chat_template=(
+                default_template if self.chat_template is None else self.chat_template
+            ),
             chat_template_content_format=default_template_content_format,
             chat_template_kwargs=merge_kwargs(
                 self.chat_template_kwargs,

vllm/entrypoints/serve/tokenize/protocol.py

@@ -135,7 +135,9 @@ def build_chat_params(
         default_template_content_format: ChatTemplateContentFormatOption,
     ) -> ChatParams:
         return ChatParams(
-            chat_template=self.chat_template or default_template,
+            chat_template=(
+                default_template if self.chat_template is None else self.chat_template
+            ),
             chat_template_content_format=default_template_content_format,
             chat_template_kwargs=merge_kwargs(
                 self.chat_template_kwargs,

vllm/renderers/params.py

@@ -270,7 +270,7 @@ def with_kwargs(self, **tokenization_kwargs: Any):
         )
 
         # https://huggingface.co/docs/transformers/en/pad_truncation
-        if padding := tokenization_kwargs.pop("padding", None):
+        if (padding := tokenization_kwargs.pop("padding", None)) is not None:
             if padding == "max_length":
                 pad_prompt_tokens = max_length
             elif padding in (False, "do_not_pad"):
@@ -279,7 +279,7 @@ def with_kwargs(self, **tokenization_kwargs: Any):
                 # To emit the below warning
                 tokenization_kwargs["padding"] = padding
 
-        if truncation := tokenization_kwargs.pop("truncation", None):
+        if (truncation := tokenization_kwargs.pop("truncation", None)) is not None:
             if truncation in (True, "longest_first"):
                 truncate_prompt_tokens = max_length
             elif truncation in (False, "do_not_truncate"):