[fix] Preserve subgraph structure when clearing workflow (#4567)

Co-authored-by: github-actions <github-actions@github.com>

src/utils/graphTraversalUtil.ts

@@ -3,6 +3,8 @@ import type { LGraph, LGraphNode, Subgraph } from '@comfyorg/litegraph'
 import type { NodeLocatorId } from '@/types/nodeIdentification'
 import { parseNodeLocatorId } from '@/types/nodeIdentification'
 
+import { isSubgraphIoNode } from './typeGuardUtil'
+
 /**
  * Parses an execution ID into its component parts.
  *
@@ -338,3 +340,14 @@ export function mapSubgraphNodes<T>(
     return undefined
   })
 }
+
+/**
+ * Gets all non-IO nodes from a subgraph (excludes SubgraphInputNode and SubgraphOutputNode).
+ * These are the user-created nodes that can be safely removed when clearing a subgraph.
+ *
+ * @param subgraph - The subgraph to get non-IO nodes from
+ * @returns Array of non-IO nodes (user-created nodes)
+ */
+export function getAllNonIoNodesInSubgraph(subgraph: Subgraph): LGraphNode[] {
+  return subgraph.nodes.filter((node) => !isSubgraphIoNode(node))
+}

src/utils/typeGuardUtil.ts

@@ -27,3 +27,16 @@ export const isSubgraph = (
  */
 export const isNonNullish = <T>(item: T | undefined | null): item is T =>
   item != null
+
+/**
+ * Type guard to check if a node is a subgraph input/output node.
+ * These nodes are essential to subgraph structure and should not be removed.
+ */
+export const isSubgraphIoNode = (
+  node: LGraphNode
+): node is LGraphNode & {
+  constructor: { comfyClass: 'SubgraphInputNode' | 'SubgraphOutputNode' }
+} => {
+  const nodeClass = node.constructor?.comfyClass
+  return nodeClass === 'SubgraphInputNode' || nodeClass === 'SubgraphOutputNode'
+}