fix: show Missing Nodes dialog for missing node prompt errors (#8511)

## Summary
When a workflow is queued with a missing node type, show the Missing
Nodes dialog instead of a generic error toast. This gives users
actionable options like "Open Manager" and "Install All".

## Changes
- Detect `missing_node_type` error from backend in `queuePrompt()` catch
block
- Construct `MissingNodeType` object with class type and contextual hint
- Reuse existing `showMissingNodesError()` to trigger the dialog

## Dependencies
⚠️ **Requires backend PR:**
https://github.com/Comfy-Org/ComfyUI/pull/12177

The backend PR changes the error type from `invalid_prompt` to
`missing_node_type` and adds `extra_info` with node details.

## Related
- Fixes COM-12528
- Addresses ~49 GitHub issues with confusing "missing class_type" errors

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8511-fix-show-Missing-Nodes-dialog-for-missing-node-prompt-errors-2f96d73d3650812b95f0f08e51abaabb)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Amp <amp@ampcode.com>

src/scripts/app.ts

@@ -70,6 +70,8 @@ import type { ComfyExtension, MissingNodeType } from '@/types/comfy'
 import { type ExtensionManager } from '@/types/extensionTypes'
 import type { NodeExecutionId } from '@/types/nodeIdentification'
 import { graphToPrompt } from '@/utils/executionUtil'
+import type { MissingNodeTypeExtraInfo } from '@/workbench/extensions/manager/types/missingNodeErrorTypes'
+import { createMissingNodeTypeFromError } from '@/workbench/extensions/manager/utils/missingNodeErrorUtil'
 import { anyItemOverlapsRect } from '@/utils/mathUtil'
 import { collectAllNodes, forEachNode } from '@/utils/graphTraversalUtil'
 import {
@@ -1394,10 +1396,21 @@ export class ComfyApp {
               } catch (error) {}
             }
           } catch (error: unknown) {
-            useDialogService().showErrorDialog(error, {
-              title: t('errorDialog.promptExecutionError'),
-              reportType: 'promptExecutionError'
-            })
+            if (
+              error instanceof PromptExecutionError &&
+              typeof error.response.error === 'object' &&
+              error.response.error?.type === 'missing_node_type'
+            ) {
+              const extraInfo = (error.response.error.extra_info ??
+                {}) as MissingNodeTypeExtraInfo
+              const missingNodeType = createMissingNodeTypeFromError(extraInfo)
+              this.showMissingNodesError([missingNodeType])
+            } else {
+              useDialogService().showErrorDialog(error, {
+                title: t('errorDialog.promptExecutionError'),
+                reportType: 'promptExecutionError'
+              })
+            }
             console.error(error)
 
             if (error instanceof PromptExecutionError) {

src/workbench/extensions/manager/types/missingNodeErrorTypes.ts

@@ -0,0 +1,9 @@
+/**
+ * Extra info returned by the backend for missing_node_type errors
+ * from the /prompt endpoint validation.
+ */
+export interface MissingNodeTypeExtraInfo {
+  class_type?: string | null
+  node_title?: string | null
+  node_id?: string
+}

src/workbench/extensions/manager/utils/missingNodeErrorUtil.test.ts

@@ -0,0 +1,90 @@
+import { describe, expect, it } from 'vitest'
+
+import {
+  buildMissingNodeHint,
+  createMissingNodeTypeFromError
+} from './missingNodeErrorUtil'
+
+describe('buildMissingNodeHint', () => {
+  it('returns hint with title and node ID when both available', () => {
+    expect(buildMissingNodeHint('My Node', 'MyNodeClass', '42')).toBe(
+      '"My Node" (Node ID #42)'
+    )
+  })
+
+  it('returns hint with title only when no node ID', () => {
+    expect(buildMissingNodeHint('My Node', 'MyNodeClass', undefined)).toBe(
+      '"My Node"'
+    )
+  })
+
+  it('returns hint with node ID only when title matches class type', () => {
+    expect(buildMissingNodeHint('MyNodeClass', 'MyNodeClass', '42')).toBe(
+      'Node ID #42'
+    )
+  })
+
+  it('returns undefined when title matches class type and no node ID', () => {
+    expect(
+      buildMissingNodeHint('MyNodeClass', 'MyNodeClass', undefined)
+    ).toBeUndefined()
+  })
+
+  it('returns undefined when title is null and no node ID', () => {
+    expect(buildMissingNodeHint(null, 'MyNodeClass', undefined)).toBeUndefined()
+  })
+
+  it('returns node ID hint when title is null but node ID exists', () => {
+    expect(buildMissingNodeHint(null, 'MyNodeClass', '42')).toBe('Node ID #42')
+  })
+})
+
+describe('createMissingNodeTypeFromError', () => {
+  it('returns string type when no hint is generated', () => {
+    const result = createMissingNodeTypeFromError({
+      class_type: 'MyNodeClass',
+      node_title: 'MyNodeClass'
+    })
+    expect(result).toBe('MyNodeClass')
+  })
+
+  it('returns object with hint when title differs from class type', () => {
+    const result = createMissingNodeTypeFromError({
+      class_type: 'MyNodeClass',
+      node_title: 'My Custom Title',
+      node_id: '42'
+    })
+    expect(result).toEqual({
+      type: 'MyNodeClass',
+      hint: '"My Custom Title" (Node ID #42)'
+    })
+  })
+
+  it('handles null class_type by defaulting to Unknown', () => {
+    const result = createMissingNodeTypeFromError({
+      class_type: null,
+      node_title: 'Some Title',
+      node_id: '42'
+    })
+    expect(result).toEqual({
+      type: 'Unknown',
+      hint: '"Some Title" (Node ID #42)'
+    })
+  })
+
+  it('handles empty extra_info', () => {
+    const result = createMissingNodeTypeFromError({})
+    expect(result).toBe('Unknown')
+  })
+
+  it('returns object with node ID hint when only node_id is available', () => {
+    const result = createMissingNodeTypeFromError({
+      class_type: 'MyNodeClass',
+      node_id: '123'
+    })
+    expect(result).toEqual({
+      type: 'MyNodeClass',
+      hint: 'Node ID #123'
+    })
+  })
+})

src/workbench/extensions/manager/utils/missingNodeErrorUtil.ts

@@ -0,0 +1,37 @@
+import type { MissingNodeType } from '@/types/comfy'
+
+import type { MissingNodeTypeExtraInfo } from '../types/missingNodeErrorTypes'
+
+/**
+ * Builds a hint string from missing node metadata.
+ * Provides context about which node is missing (title, ID) when available.
+ */
+export function buildMissingNodeHint(
+  nodeTitle: string | null | undefined,
+  classType: string,
+  nodeId: string | undefined
+): string | undefined {
+  const hasTitle = nodeTitle && nodeTitle !== classType
+  if (hasTitle && nodeId) {
+    return `"${nodeTitle}" (Node ID #${nodeId})`
+  } else if (hasTitle) {
+    return `"${nodeTitle}"`
+  } else if (nodeId) {
+    return `Node ID #${nodeId}`
+  }
+  return undefined
+}
+
+/**
+ * Creates a MissingNodeType from backend error extra_info.
+ * Used when the /prompt endpoint returns a missing_node_type error.
+ */
+export function createMissingNodeTypeFromError(
+  extraInfo: MissingNodeTypeExtraInfo
+): MissingNodeType {
+  const classType = extraInfo.class_type ?? 'Unknown'
+  const nodeTitle = extraInfo.node_title ?? classType
+  const hint = buildMissingNodeHint(nodeTitle, classType, extraInfo.node_id)
+
+  return hint ? { type: classType, hint } : classType
+}