Add support for dynamic widgets (#6661)

Adds support for "dynamic combo" widgets where selecting a value on a
combo widget can cause other widgets or inputs to be created.


![dynamic-widgets_00001](https://github.com/user-attachments/assets/c797d008-f335-4d4e-9b2e-6fe4a7187ba7)

Includes a fairly large refactoring in litegraphService to remove
`#private` methods and cleanup some duplication in constructors for
subgraphNodes.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6661-Add-support-for-dynamic-widgets-2a96d73d3650817aa570c7babbaca2f3)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Alexander Brown <drjkl@comfy.org>

tests-ui/tests/widgets/dynamicCombo.test.ts

@@ -0,0 +1,90 @@
+import { setActivePinia } from 'pinia'
+import { createTestingPinia } from '@pinia/testing'
+import { describe, expect, test } from 'vitest'
+import { LGraphNode } from '@/lib/litegraph/src/litegraph'
+import { transformInputSpecV1ToV2 } from '@/schemas/nodeDef/migration'
+import type { InputSpec } from '@/schemas/nodeDefSchema'
+import { useLitegraphService } from '@/services/litegraphService'
+import type { HasInitialMinSize } from '@/services/litegraphService'
+
+setActivePinia(createTestingPinia())
+type DynamicInputs = ('INT' | 'STRING' | 'IMAGE' | DynamicInputs)[][]
+
+const { addNodeInput } = useLitegraphService()
+
+function addDynamicCombo(node: LGraphNode, inputs: DynamicInputs) {
+  const namePrefix = `${node.widgets?.length ?? 0}`
+  function getSpec(
+    inputs: DynamicInputs,
+    depth: number = 0
+  ): { key: string; inputs: object }[] {
+    return inputs.map((group, groupIndex) => {
+      const inputs = group.map((input, inputIndex) => [
+        `${namePrefix}.${depth}.${inputIndex}`,
+        Array.isArray(input)
+          ? ['COMFY_DYNAMICCOMBO_V3', { options: getSpec(input, depth + 1) }]
+          : [input, {}]
+      ])
+      return {
+        key: `${groupIndex}`,
+        inputs: { required: Object.fromEntries(inputs) }
+      }
+    })
+  }
+  const inputSpec: Required<InputSpec> = [
+    'COMFY_DYNAMICCOMBO_V3',
+    { options: getSpec(inputs) }
+  ]
+  addNodeInput(
+    node,
+    transformInputSpecV1ToV2(inputSpec, { name: namePrefix, isOptional: false })
+  )
+}
+function testNode() {
+  const node: LGraphNode & Partial<HasInitialMinSize> = new LGraphNode('test')
+  node.widgets = []
+  node._initialMinSize = { width: 1, height: 1 }
+  node.constructor.nodeData = {
+    name: 'testnode'
+  } as typeof node.constructor.nodeData
+  return node as LGraphNode & Required<Pick<LGraphNode, 'widgets'>>
+}
+
+describe('Dynamic Combos', () => {
+  test('Can add widget on selection', () => {
+    const node = testNode()
+    addDynamicCombo(node, [['INT'], ['INT', 'STRING']])
+    expect(node.widgets.length).toBe(2)
+    node.widgets[0].value = '1'
+    expect(node.widgets.length).toBe(3)
+  })
+  test('Can add nested widgets', () => {
+    const node = testNode()
+    addDynamicCombo(node, [['INT'], [[[], ['STRING']]]])
+    expect(node.widgets.length).toBe(2)
+    node.widgets[0].value = '1'
+    expect(node.widgets.length).toBe(2)
+    node.widgets[1].value = '1'
+    expect(node.widgets.length).toBe(3)
+  })
+  test('Can add input', () => {
+    const node = testNode()
+    addDynamicCombo(node, [['INT'], ['IMAGE']])
+    expect(node.widgets.length).toBe(2)
+    node.widgets[0].value = '1'
+    expect(node.widgets.length).toBe(1)
+    expect(node.inputs.length).toBe(2)
+    expect(node.inputs[1].type).toBe('IMAGE')
+  })
+  test('Dynamically added inputs are well ordered', () => {
+    const node = testNode()
+    addDynamicCombo(node, [['INT'], ['IMAGE']])
+    addDynamicCombo(node, [['INT'], ['IMAGE']])
+    node.widgets[2].value = '1'
+    node.widgets[0].value = '1'
+    expect(node.widgets.length).toBe(2)
+    expect(node.inputs.length).toBe(4)
+    expect(node.inputs[1].name).toBe('0.0.0')
+    expect(node.inputs[3].name).toBe('2.0.0')
+  })
+})