Getting 'DataCloneError' if function returns Promise

[omkar-kanekar1-tfs]

Describe the bug
Host exposed a function which returns "Promise". On calling that function from iframe url code, we get following error "Response object could not be cloned." If the Host function returns objects/array/string it works fine.
What is the workaround.

[alesgenova]

Functions returning promises are supported, and that's probably not where the issue is.
What type of parameters does the function take? And what is the type resolved by the Promise?

[omkar-kanekar1-tfs]

The function takes string and and object as input The promise returns fetch "Response" object. Basically we are invoking overridden version of JavaScript fetch and the same is retuned from function.

Reference:
function f(url, fetchOpt) {
return customFetch(url, fetchOpt)
}

[alesgenova]

My guess is that the Response object can't be passed across windows or workers.
See which type of objects can be natively be passed across (either as function parameters, or returned): https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm

So a work around for your use case could be to return the content of the response body instead of the Response itself.

Double check the code, but it could look something like this:

async function f(url, options) {
  let response = await fetch(url, options);
  let body = await response.json();
  return body;
}