refactor(api): Decouple ParameterExtractorNode from LLMNode (#20843)

- Extract methods used by `ParameterExtractorNode` from `LLMNode` into a separate file.
- Convert `ParameterExtractorNode` into a subclass of `BaseNode`.
- Refactor code referencing the extracted methods to ensure functionality and clarity.
- Fixes the issue that `ParameterExtractorNode` returns error when executed.
- Fix relevant test cases.

Closes #20840.

api/tests/integration_tests/workflow/nodes/test_parameter_extractor.py

@@ -353,7 +353,7 @@ def test_extract_json_from_tool_call():
     assert result["location"] == "kawaii"
 
 
-def test_chat_parameter_extractor_with_memory(setup_model_mock):
+def test_chat_parameter_extractor_with_memory(setup_model_mock, monkeypatch):
     """
     Test chat parameter extractor with memory.
     """
@@ -384,7 +384,8 @@ def test_chat_parameter_extractor_with_memory(setup_model_mock):
         mode="chat",
         credentials={"openai_api_key": os.environ.get("OPENAI_API_KEY")},
     )
-    node._fetch_memory = get_mocked_fetch_memory("customized memory")
+    # Test the mock before running the actual test
+    monkeypatch.setattr("core.workflow.nodes.llm.llm_utils.fetch_memory", get_mocked_fetch_memory("customized memory"))
     db.session.close = MagicMock()
 
     result = node._run()

api/tests/unit_tests/core/workflow/nodes/llm/test_node.py

@@ -25,6 +25,7 @@ from core.workflow.entities.variable_pool import VariablePool
 from core.workflow.graph_engine import Graph, GraphInitParams, GraphRuntimeState
 from core.workflow.nodes.answer import AnswerStreamGenerateRoute
 from core.workflow.nodes.end import EndStreamParam
+from core.workflow.nodes.llm import llm_utils
 from core.workflow.nodes.llm.entities import (
     ContextConfig,
     LLMNodeChatModelMessage,
@@ -170,7 +171,7 @@ def model_config():
     )
 
 
-def test_fetch_files_with_file_segment(llm_node):
+def test_fetch_files_with_file_segment():
     file = File(
         id="1",
         tenant_id="test",
@@ -180,13 +181,14 @@ def test_fetch_files_with_file_segment(llm_node):
         related_id="1",
         storage_key="",
     )
-    llm_node.graph_runtime_state.variable_pool.add(["sys", "files"], file)
+    variable_pool = VariablePool()
+    variable_pool.add(["sys", "files"], file)
 
-    result = llm_node._fetch_files(selector=["sys", "files"])
+    result = llm_utils.fetch_files(variable_pool=variable_pool, selector=["sys", "files"])
     assert result == [file]
 
 
-def test_fetch_files_with_array_file_segment(llm_node):
+def test_fetch_files_with_array_file_segment():
     files = [
         File(
             id="1",
@@ -207,28 +209,32 @@ def test_fetch_files_with_array_file_segment(llm_node):
             storage_key="",
         ),
     ]
-    llm_node.graph_runtime_state.variable_pool.add(["sys", "files"], ArrayFileSegment(value=files))
+    variable_pool = VariablePool()
+    variable_pool.add(["sys", "files"], ArrayFileSegment(value=files))
 
-    result = llm_node._fetch_files(selector=["sys", "files"])
+    result = llm_utils.fetch_files(variable_pool=variable_pool, selector=["sys", "files"])
     assert result == files
 
 
-def test_fetch_files_with_none_segment(llm_node):
-    llm_node.graph_runtime_state.variable_pool.add(["sys", "files"], NoneSegment())
+def test_fetch_files_with_none_segment():
+    variable_pool = VariablePool()
+    variable_pool.add(["sys", "files"], NoneSegment())
 
-    result = llm_node._fetch_files(selector=["sys", "files"])
+    result = llm_utils.fetch_files(variable_pool=variable_pool, selector=["sys", "files"])
     assert result == []
 
 
-def test_fetch_files_with_array_any_segment(llm_node):
-    llm_node.graph_runtime_state.variable_pool.add(["sys", "files"], ArrayAnySegment(value=[]))
+def test_fetch_files_with_array_any_segment():
+    variable_pool = VariablePool()
+    variable_pool.add(["sys", "files"], ArrayAnySegment(value=[]))
 
-    result = llm_node._fetch_files(selector=["sys", "files"])
+    result = llm_utils.fetch_files(variable_pool=variable_pool, selector=["sys", "files"])
     assert result == []
 
 
-def test_fetch_files_with_non_existent_variable(llm_node):
-    result = llm_node._fetch_files(selector=["sys", "files"])
+def test_fetch_files_with_non_existent_variable():
+    variable_pool = VariablePool()
+    result = llm_utils.fetch_files(variable_pool=variable_pool, selector=["sys", "files"])
     assert result == []