Nope, they need to be ArrayBuffers.

app-shell/src/usb.ts

@@ -84,10 +84,18 @@ function isUsbDeviceOt3(device: UsbDevice): boolean {
  )
 }
 
-interface StructuredCloneableFormDataEntry {
- name: string
- value: string | Blob | File
-}
+type StructuredCloneableFormDataEntry =
+ | {
+ type: 'string'
+ name: string
+ value: string
+ }
+ | {
+ type: 'file'
+ name: string
+ value: ArrayBuffer
+ filename: string
+ }
 
 type StructuredCloneableFormData = StructuredCloneableFormDataEntry[]
 
@@ -96,7 +104,9 @@ function reconstructFormData(
 ): FormData {
  const result = new FormData()
  structuredCloneableFormData.forEach(entry => {
- result.append(entry.name, entry.value)
+ entry.type === 'file'
+ ? result.append(entry.name, Buffer.from(entry.value), entry.filename)
+ : result.append(entry.name, entry.value)
  })
  return result
 }

app/src/redux/shell/remote.ts

@@ -1,5 +1,5 @@
 // access main process remote modules via attachments to `global`
-import type { AxiosRequestConfig } from 'axios'
+import type { AxiosRequestConfig, AxiosResponse } from 'axios'
 import type { ResponsePromise } from '@opentrons/api-client'
 import type { Remote, NotifyTopic, NotifyResponseData } from './types'
 
@@ -20,31 +20,55 @@ export const remote: Remote = new Proxy(emptyRemote, {
  },
 })
 
-interface StructuredCloneableFormDataEntry {
- name: string
- value: string | Blob | File
-}
+type StructuredCloneableFormDataEntry =
+ | {
+ type: 'string'
+ name: string
+ value: string
+ }
+ | {
+ type: 'file'
+ name: string
+ value: ArrayBuffer
+ filename: string
+ }
 
 type StructuredCloneableFormData = StructuredCloneableFormDataEntry[]
 
-function proxyFormData(formData: FormData): StructuredCloneableFormData {
- return [...formData.entries()].map(([name, value]) => {
- return { name, value }
- })
+async function proxyFormData(
+ formData: FormData
+): Promise<StructuredCloneableFormData> {
+ const result: StructuredCloneableFormData = []
+ for (const [name, value] of formData.entries()) {
+ if (value instanceof File) {
+ result.push({
+ type: 'file',
+ name,
+ value: await value.arrayBuffer(),
+ filename: value.name,
+ })
+ } else {
+ result.push({ type: 'string', name, value })
+ }
+ }
+
+ return result
 }
 
-export function appShellRequestor<Data>(
+export async function appShellRequestor<Data>(
  config: AxiosRequestConfig
-): ResponsePromise<Data> {
+): Promise<AxiosResponse<Data>> {
  const { data } = config
  // Special case: FormData objects can't be sent through invoke().
  // Convert it to a structured-cloneable object so it can be.
  // app-shell will convert it back.
  const formDataProxy =
- data instanceof FormData ? { proxiedFormData: proxyFormData(data) } : data
+ data instanceof FormData
+ ? { proxiedFormData: await proxyFormData(data) }
+ : data
  const configProxy = { ...config, data: formDataProxy }
 
- return remote.ipcRenderer.invoke('usb:request', configProxy)
+ return await remote.ipcRenderer.invoke('usb:request', configProxy)
 }
 
 interface CallbackStore {