feat: Persist Variables for Enhanced Debugging Workflow (#20699)

This pull request introduces a feature aimed at improving the debugging experience during workflow editing. With the addition of variable persistence, the system will automatically retain the output variables from previously executed nodes. These persisted variables can then be reused when debugging subsequent nodes, eliminating the need for repetitive manual input.

By streamlining this aspect of the workflow, the feature minimizes user errors and significantly reduces debugging effort, offering a smoother and more efficient experience.

Key highlights of this change:

- Automatic persistence of output variables for executed nodes.
- Reuse of persisted variables to simplify input steps for nodes requiring them (e.g., `code`, `template`, `variable_assigner`).
- Enhanced debugging experience with reduced friction.

Closes #19735.

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

@@ -12,7 +12,7 @@ from core.tools.entities.tool_entities import ToolInvokeMessage, ToolParameter
 from core.tools.errors import ToolInvokeError
 from core.tools.tool_engine import ToolEngine
 from core.tools.utils.message_transformer import ToolFileMessageTransformer
-from core.variables.segments import ArrayAnySegment
+from core.variables.segments import ArrayAnySegment, ArrayFileSegment
 from core.variables.variables import ArrayAnyVariable
 from core.workflow.entities.node_entities import NodeRunResult
 from core.workflow.entities.variable_pool import VariablePool
@@ -44,6 +44,10 @@ class ToolNode(BaseNode[ToolNodeData]):
     _node_data_cls = ToolNodeData
     _node_type = NodeType.TOOL
 
+    @classmethod
+    def version(cls) -> str:
+        return "1"
+
     def _run(self) -> Generator:
         """
         Run the tool node
@@ -300,6 +304,7 @@ class ToolNode(BaseNode[ToolNodeData]):
                     variables[variable_name] = variable_value
             elif message.type == ToolInvokeMessage.MessageType.FILE:
                 assert message.meta is not None
+                assert isinstance(message.meta, File)
                 files.append(message.meta["file"])
             elif message.type == ToolInvokeMessage.MessageType.LOG:
                 assert isinstance(message.message, ToolInvokeMessage.LogMessage)
@@ -363,7 +368,7 @@ class ToolNode(BaseNode[ToolNodeData]):
         yield RunCompletedEvent(
             run_result=NodeRunResult(
                 status=WorkflowNodeExecutionStatus.SUCCEEDED,
-                outputs={"text": text, "files": files, "json": json, **variables},
+                outputs={"text": text, "files": ArrayFileSegment(value=files), "json": json, **variables},
                 metadata={
                     **agent_execution_metadata,
                     WorkflowNodeExecutionMetadataKey.TOOL_INFO: tool_info,