[Model] Add DeepSeek-V3.1 reasoning parser (split from PR #24972) (#25589)

Signed-off-by: taohui <taohui3@gmail.com>
Signed-off-by: Tao Hui <taohui3@gmail.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: Chauncey <chaunceyjiang@gmail.com>

tests/reasoning/test_deepseekv3_reasoning_parser.py

@@ -0,0 +1,76 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import pytest
+from transformers import AutoTokenizer
+
+from vllm.entrypoints.openai.protocol import ChatCompletionRequest, DeltaMessage
+from vllm.reasoning import (
+    DeepSeekR1ReasoningParser,
+    DeepSeekV3ReasoningParser,
+    IdentityReasoningParser,
+)
+
+REASONING_MODEL_NAME = "deepseek-ai/DeepSeek-V3.1"
+
+
+@pytest.fixture(scope="module")
+def tokenizer():
+    return AutoTokenizer.from_pretrained(REASONING_MODEL_NAME)
+
+
+@pytest.mark.parametrize(
+    "thinking,expected_parser_type",
+    [
+        (True, DeepSeekR1ReasoningParser),
+        (False, IdentityReasoningParser),
+    ],
+)
+def test_parser_selection(tokenizer, thinking, expected_parser_type):
+    parser = DeepSeekV3ReasoningParser(
+        tokenizer, chat_template_kwargs={"thinking": thinking}
+    )
+
+    assert isinstance(parser._parser, expected_parser_type)
+
+
+def test_identity_reasoning_parser_basic(tokenizer):
+    parser = IdentityReasoningParser(tokenizer)
+
+    # Test is_reasoning_end always returns True
+    input_text = "This is some output"
+    input_tokens = tokenizer.tokenize(input_text)
+    input_ids = tokenizer.convert_tokens_to_ids(input_tokens)
+    assert parser.is_reasoning_end(input_ids) is True
+
+    # Test extract_content_ids returns all input_ids
+    assert parser.extract_content_ids(input_ids) == input_ids
+
+    # Test extract_reasoning_content returns (None, model_output)
+    request = ChatCompletionRequest(model="test-model", messages=[], temperature=1.0)
+    reasoning, content = parser.extract_reasoning_content(input_text, request)
+    assert reasoning is None
+    assert content == input_text
+
+    # Test extract_reasoning_content_streaming returns DeltaMessage or None
+    result = parser.extract_reasoning_content_streaming(
+        previous_text="",
+        current_text="Hello world",
+        delta_text="Hello world",
+        previous_token_ids=[],
+        current_token_ids=input_ids,
+        delta_token_ids=input_ids,
+    )
+    assert isinstance(result, DeltaMessage)
+    assert result.content == "Hello world"
+
+    # If delta_text is empty, should return None
+    result_none = parser.extract_reasoning_content_streaming(
+        previous_text="Hello world",
+        current_text="Hello world",
+        delta_text="",
+        previous_token_ids=input_ids,
+        current_token_ids=input_ids,
+        delta_token_ids=[],
+    )
+    assert result_none is None