Abstraction for IPC Renderer Service to Handle Custom Error Objects

ipc_renderer_service.ts

/**
 * This exists because `ipcMain.handle` does not allow
 * you to return rejected Promises with custom data.
 * You can throw an error in `handle` but it can only
 * be a string or existing error object. This means all
 * the error processing logic must live in main process
 * in order to figure what string or error type to throw
 * in `handle`.
 *
 * This abstract allows us to send messages to `handle`.
 * If `handle` resolves to message with `rejected` equal
 * to true then this method throws an error with the object
 * that is cotained in the resolved promise. Everything else
 * is the same.
 *
 * This allows us to get custom error objects and use catch
 * in `ipc.invoke` calls. It also frees us to remove all the
 * error catching from `then` - since all failures will be
 * caught in ipcMain and rethrown here.
 *
 * https://github.com/electron/electron/issues/24427
 * https://github.com/electron/electron/issues/25196
 */
import { ipcRenderer } from 'electron'


async function invoke(channel: string, args?: any) {
  try {

    const response = await ipcRenderer.invoke(channel, args)
    if (isRejectedPromise(response))
      throw response
    else
      return response

  } catch (error: any) {

    console.warn(
      '[IpcRendererService.invoke] threw an error or promise was rejected',
      { error },
    )
    return new Promise((_, reject) => reject(error))

  }
}


function isRejectedPromise(response_from_ipc_main: any) {
  if (response_from_ipc_main === undefined)
    return false
  else if (response_from_ipc_main.handle_as_rejected_promise)
    return true
  else
    return false
}


export default {
  invoke
}