fix(workflows): offer no child fields for arrays of typed elements

The connection panel listed an items child for an array whose elements are a
typed node without properties, such as an MCP array of strings or of untyped
elements, offering an invalid reference.

Author: waleedlatif1

apps/sim/app/workspace/[workspaceId]/w/[workflowId]/hooks/use-block-output-fields.test.ts

@@ -0,0 +1,23 @@
+/**
+ * @vitest-environment node
+ */
+import { describe, expect, it } from 'vitest'
+import { createFieldFromOutput } from '@/app/workspace/[workspaceId]/w/[workflowId]/hooks/use-block-output-fields'
+
+describe('createFieldFromOutput', () => {
+  it.each([
+    ['untyped elements', { type: 'any' }],
+    ['primitive elements', { type: 'string' }],
+  ])('offers no child fields for an array of %s', (_, items) => {
+    const field = createFieldFromOutput('rows', { type: 'array', items })
+    expect(field.children).toBeUndefined()
+  })
+
+  it('offers the declared fields of object elements', () => {
+    const field = createFieldFromOutput('rows', {
+      type: 'array',
+      items: { type: 'object', properties: { id: { type: 'string' } } },
+    })
+    expect(field.children?.map((child) => child.name)).toEqual(['id'])
+  })
+})

apps/sim/app/workspace/[workspaceId]/w/[workflowId]/hooks/use-block-output-fields.ts

@@ -35,6 +35,11 @@ const extractChildFields = (prop: any): SchemaField[] | undefined => {
     return extractNestedFields(prop.items.properties)
   }
 
+  /** Typed elements without `properties` (strings, `any`) have no fields to reference. */
+  if (isObject(prop.items) && typeof prop.items.type === 'string') {
+    return undefined
+  }
+
   if (!('type' in prop)) {
     return extractNestedFields(prop)
   }
@@ -71,7 +76,7 @@ const extractNestedFields = (properties: Record<string, any>): SchemaField[] =>
 /**
  * Creates a schema field from an output definition
  */
-const createFieldFromOutput = (name: string, output: any): SchemaField => {
+export const createFieldFromOutput = (name: string, output: any): SchemaField => {
   const hasExplicitType = isObject(output) && typeof output.type === 'string'
   const type = hasExplicitType ? output.type : isObject(output) ? 'object' : 'string'