refactor(api/core/app/segments): Support more kinds of Segments. (#6706)

Signed-off-by: -LAN- <laipz8200@outlook.com>

api/core/workflow/entities/variable_pool.py

@@ -4,7 +4,7 @@ from typing import Any, Union
 
 from typing_extensions import deprecated
 
-from core.app.segments import Variable, factory
+from core.app.segments import Segment, Variable, factory
 from core.file.file_obj import FileVar
 from core.workflow.entities.node_entities import SystemVariable
 
@@ -33,7 +33,7 @@ class VariablePool:
         # The first element of the selector is the node id, it's the first-level key in the dictionary.
         # Other elements of the selector are the keys in the second-level dictionary. To get the key, we hash the
         # elements of the selector except the first one.
-        self._variable_dictionary: dict[str, dict[int, Variable]] = defaultdict(dict)
+        self._variable_dictionary: dict[str, dict[int, Segment]] = defaultdict(dict)
 
         # TODO: This user inputs is not used for pool.
         self.user_inputs = user_inputs
@@ -67,15 +67,15 @@ class VariablePool:
         if value is None:
             return
 
-        if not isinstance(value, Variable):
-            v = factory.build_anonymous_variable(value)
-        else:
+        if isinstance(value, Segment):
             v = value
+        else:
+            v = factory.build_segment(value)
 
         hash_key = hash(tuple(selector[1:]))
         self._variable_dictionary[selector[0]][hash_key] = v
 
-    def get(self, selector: Sequence[str], /) -> Variable | None:
+    def get(self, selector: Sequence[str], /) -> Segment | None:
         """
         Retrieves the value from the variable pool based on the given selector.
 

api/core/workflow/nodes/tool/tool_node.py

@@ -126,6 +126,7 @@ class ToolNode(BaseNode):
             else:
                 tool_input = node_data.tool_parameters[parameter_name]
                 if tool_input.type == 'variable':
+                    # TODO: check if the variable exists in the variable pool
                     parameter_value = variable_pool.get(tool_input.value).value
                 else:
                     segment_group = parser.convert_template(