[Web Install] Distinguish AbortErrors caused by user cancellation

[LiaHiscock]

Currently, navigator.install()'s promise can resolve in 1 of 3 ways

1. Success
2. AbortError: The user aborted a request.
3. DataError: The data provided does not meet requirements.

For privacy reasons, AbortError is used as a generic failure code for any non-data related errors. This includes if the user declines the installation dialog.

We should consider changing the message string so that it only says "The user aborted a request" when the user actually clicked "cancel" in the install confirmation prompt.

Motivation - enables developers to show an error message only if something actually failed, and not if the user cancelled installation.

[JudahGabriel]

We should consider changing the message string so that it only says "The user aborted a request" when the user actually clicked "cancel" in the install confirmation prompt.

Does that error message change based on browser locale? If so, I'd suggest an alternative that doesn't rely on error message string.

As a developer I want to do this:

try {
   navigator.install(url, manifestId);
} catch (error) {
   // If the user cancelled, log it. Otherwise, show an error to the user.
   const isUserCancellation = ...; // how?
   if (isUserCancellation) {
      telemetry.log("WebInstallCancelled", error);
   } else {
      showErrorInUI(error); 
   }
}

Today, I can't reliably do that. I can check if there's a data error, but if it's an AbortError, it could be the user cancelling, or it could be some other problem.

[LiaHiscock]

@JudahGabriel Ah good point. Sounds like we may actually want separate DOM exceptions then for user cancellation vs other generic failures. Thanks!