IMO, it would be ideal to the function called throw an Exception instead..

But I can see that something like package:http won't throw on 5xx responses, you if you want to retry those, this would be pretty neat.

quick note: I wonder if we could call it retryIfValue instead of retryIfReturnedObject which rather long...
Or maybe retryOnReturnIf, other good names?

retryValueIf might be solid..

Maybe we could just rename the parameters to be more descriptive, for example:

final response = await retry(
    // Make a GET request
    () => http.get('https://google.com'),
    // Retry on Exception
    retryOnException: (e) => e is SocketException,
    retryOnSuccess: (o) => o == "retry-please"
);

That's exactly the thing I missed/ I'd like to suggest!

I like @Ascenio's idea to rename the parameters (although it is a breaking change, which requires users to adjust their code). I'd prefer an even 'simpler' renaming like the following:

final response = await retry(
    // Make a GET request
    () => http.get('https://google.com'),
    // Retry on Exception
    retryOnException: (e) => e is SocketException, // or could also be "retryOnError" - sounds even better to me
    retryIf: (o) => o == "retry-please"

);

This would have been the 'intuitive' API I would have expected on my first use.
Overall thanks for considering this and BR

How about:
retryIf (for exceptions)
retryOn (for values)

We don't break anything this way

any news ?