enh: The addition of the think closure tag supports multi-turn thin… (#267)

* ENH: The addition of the `think` closure tag supports multi-turn thinking scenarios.

* fix lint

* add test

* fix lint

* fix lint

* fix lint

* fix lint

* add  unittest

* fix lint

* fix lint

Author: leslie2046

python/dify_plugin/interfaces/model/large_language_model.py

@@ -536,17 +536,22 @@ def _wrap_thinking_by_reasoning_content(self, delta: dict, is_reasoning: bool) -
 
         content = delta.get("content") or ""
         reasoning_content = delta.get("reasoning_content")
-
+        output = content
         if reasoning_content:
             if not is_reasoning:
-                content = "<think>\n" + reasoning_content
+                output = "<think>\n" + reasoning_content
                 is_reasoning = True
             else:
-                content = reasoning_content
-        elif is_reasoning and content:
-            content = "\n</think>" + content
-            is_reasoning = False
-        return content, is_reasoning
+                output = reasoning_content
+        else:
+            if is_reasoning:
+                is_reasoning = False
+                if not reasoning_content:
+                    output = "\n</think>"
+                if content:
+                    output += content
+
+        return output, is_reasoning
 
     ############################################################
     #                 For executor use only                    #

python/tests/interfaces/model/test_wrap_think.py

@@ -0,0 +1,111 @@
+import unittest
+
+from dify_plugin.entities.model import AIModelEntity, ModelPropertyKey, ModelType
+from dify_plugin.entities.model.llm import LLMMode, LLMResult
+from dify_plugin.interfaces.model.large_language_model import LargeLanguageModel
+
+
+class MockLLM(LargeLanguageModel):
+    """
+    Concrete Mock class for testing non-abstract methods of LargeLanguageModel.
+    """
+
+    def _invoke(
+        self,
+        model: str,
+        credentials: dict,
+        prompt_messages: list,
+        model_parameters: dict,
+        tools: list,
+        stop: list,
+        stream: bool,
+        user: str,
+    ) -> LLMResult:
+        pass
+
+    def get_num_tokens(self, model: str, credentials: dict, prompt_messages: list, tools: list) -> int:
+        return 0
+
+    def validate_credentials(self, model: str, credentials: dict) -> None:
+        pass
+
+    @property
+    def _invoke_error_mapping(self) -> dict:
+        return {}
+
+
+class TestWrapThinking(unittest.TestCase):
+    def setUp(self):
+        # Create a dummy model schema to satisfy AIModel.__init__
+        dummy_schema = AIModelEntity(
+            model="mock_model",
+            label={"en_US": "Mock Model"},
+            model_type=ModelType.LLM,
+            features=[],
+            model_properties={ModelPropertyKey.MODE: LLMMode.CHAT.value, ModelPropertyKey.CONTEXT_SIZE: 4096},
+            parameter_rules=[],
+            pricing=None,
+            deprecated=False,
+        )
+        self.llm = MockLLM(model_schemas=[dummy_schema])
+
+    def test_wrap_thinking_logic_closure(self):
+        """
+        Test that when reasoning_content ends, even if content is empty (e.g. followed immediately by tool_calls),
+        the <think> tag should be closed correctly.
+        """
+
+        # Simulate simulated streaming data:
+        # 1. Has reasoning_content
+        # 2. reasoning_content ends, followed immediately by tool_calls (content is None)
+
+        chunks = [
+            # Chunk 1: Thinking started
+            {"reasoning_content": "Thinking started.", "content": ""},
+            # Chunk 2: Still thinking
+            {"reasoning_content": " Still thinking.", "content": ""},
+            # Chunk 3: Thinking ended, transitioned to Tool Call (reasoning_content=None, content=None/Empty)
+            # This is a critical point, old logic would fail here because content is empty
+            {"reasoning_content": None, "content": "", "tool_calls": [{"id": "call_1", "function": {}}]},
+            # Chunk 4: Subsequent tool parameter stream
+            {"reasoning_content": None, "content": "", "tool_calls": [{"function": {"arguments": "{"}}]},
+        ]
+
+        # Use the "new logic" from PR for testing.
+        # We can directly call self.llm._wrap_thinking_by_reasoning_content.
+
+        # Assume we are testing the logic function itself:
+        is_reasoning = False
+        full_output = ""
+
+        for chunk in chunks:
+            # Directly call the implementation in SDK to verify real code logic
+            output, is_reasoning = self.llm._wrap_thinking_by_reasoning_content(chunk, is_reasoning)
+            full_output += output
+
+        # Verify results
+        print(f"DEBUG Output: {full_output!r}")
+
+        assert "<think>" in full_output
+        assert "Thinking started. Still thinking." in full_output
+        assert "</think>" in full_output, "Should verify <think> tag is closed properly"
+
+        # Verify the position of the closing tag: should be after the thinking content
+        expected_part = "Thinking started. Still thinking.\n</think>"
+        assert expected_part in full_output
+
+    def test_standard_reasoning_flow(self):
+        """Test standard reasoning -> text flow"""
+        chunks = [
+            {"reasoning_content": "Thinking.", "content": ""},
+            {"reasoning_content": None, "content": "Hello world."},
+        ]
+
+        is_reasoning = False
+        full_output = ""
+        for chunk in chunks:
+            # Directly call the implementation in SDK
+            output, is_reasoning = self.llm._wrap_thinking_by_reasoning_content(chunk, is_reasoning)
+            full_output += output
+
+        assert full_output == "<think>\nThinking.\n</think>Hello world."