fix: Introduce ArrayVariable and update iteration node to handle it (#12001)

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

api/core/workflow/nodes/iteration/iteration_node.py

@@ -9,7 +9,7 @@ from typing import TYPE_CHECKING, Any, Optional, cast
 from flask import Flask, current_app
 
 from configs import dify_config
-from core.variables import IntegerVariable
+from core.variables import ArrayVariable, IntegerVariable, NoneVariable
 from core.workflow.entities.node_entities import (
     NodeRunMetadataKey,
     NodeRunResult,
@@ -75,12 +75,15 @@ class IterationNode(BaseNode[IterationNodeData]):
         """
         Run the node.
         """
-        iterator_list_segment = self.graph_runtime_state.variable_pool.get(self.node_data.iterator_selector)
+        variable = self.graph_runtime_state.variable_pool.get(self.node_data.iterator_selector)
 
-        if not iterator_list_segment:
-            raise IteratorVariableNotFoundError(f"Iterator variable {self.node_data.iterator_selector} not found")
+        if not variable:
+            raise IteratorVariableNotFoundError(f"iterator variable {self.node_data.iterator_selector} not found")
 
-        if len(iterator_list_segment.value) == 0:
+        if not isinstance(variable, ArrayVariable) and not isinstance(variable, NoneVariable):
+            raise InvalidIteratorValueError(f"invalid iterator value: {variable}, please provide a list.")
+
+        if isinstance(variable, NoneVariable) or len(variable.value) == 0:
             yield RunCompletedEvent(
                 run_result=NodeRunResult(
                     status=WorkflowNodeExecutionStatus.SUCCEEDED,
@@ -89,7 +92,7 @@ class IterationNode(BaseNode[IterationNodeData]):
             )
             return
 
-        iterator_list_value = iterator_list_segment.to_object()
+        iterator_list_value = variable.to_object()
 
         if not isinstance(iterator_list_value, list):
             raise InvalidIteratorValueError(f"Invalid iterator value: {iterator_list_value}, please provide a list.")