[google_sign_in_ios] handle restorePreviousSignIn invalid grant exception

[felangel]

Description

Adds exception handling to _getAuthorizationTokens to handle PlatformExceptions thrown by restorePreviousSignIn. This fixes a bug that would cause authorizeServer to throw a PlatformException due to an expired or revoked token.

• closes [google_sign_in_ios] restorePreviousSignIn can throw PlatformException due to invalid grant flutter#184134

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Code Review

This pull request enhances the google_sign_in_ios package by adding error handling for restorePreviousSignIn() calls. It now includes a try-catch block to manage exceptions, specifically when tokens are expired or revoked, and attempts a new sign-in in such cases. A corresponding test has been added to validate this new behavior. Feedback suggests refining the exception handling to catch PlatformException instead of a general Exception for better error specificity.

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[stuartmorgan-g]

The intended design of this plugin is that we catch errors on the native side, where we still have full context. What exactly is throwing here? Is this throwing instead of calling the completion handler?

If so, we should catch it there, inspect the error, and turn this specific one into a known error value, and anything else into an unknown error, via the error return system used by all the other native code in this plugin. (We should also file an issue upstream if that's the case, since that would be surprising behavior.)

[felangel]

The intended design of this plugin is that we catch errors on the native side, where we still have full context. What exactly is throwing here? Is this throwing instead of calling the completion handler?

I believe that is correct 👍

If so, we should catch it there, inspect the error, and turn this specific one into a known error value, and anything else into an unknown error, via the error return system used by all the other native code in this plugin.

Okay I can try to spend some time on that later this week. Feel free to take this over if you get to it before me.

We should also file an issue upstream if that's the case, since that would be surprising behavior.

Where exactly should this issue be filed?

[stuartmorgan-g]

Where exactly should this issue be filed?

If the Google Sign In SDK is throwing an exception instead of calling the callback, that should be filed here.