[Feature Request] The cache serialization callbacks should accept CancellationToken

Even though the cache serialization callbacks return a Task, they do not accept a CancellationToken. Example is the SetBeforeAccessAsync

Accepting a CancellationToken as a parameter is important as partners onboard to distributed caches and invoke the MSAL APIs with a CancellationToken at the ExecuteAsync API.

[bgavrilMS]

I think Id.Web does consume it. The code is somewhat unclear, because we exposed an abstract class there and we chose to extend it using the “CacheSerializationHints” object, which contains the token. For example see https://github.com/AzureAD/microsoft-identity-web/blob/34325b3ae90fa84763a78ee454a3080bb07ae92f/src/Microsoft.Identity.Web.TokenCache/Distributed/MsalDistributedTokenCacheAdapter.cs#L261

Lessons learned:

• “config” objects are a good way to extend functionality without breaking interfaces (or abstract classes, but I am not a fan of those)
• never have an async method without a cancelation token.

[bgavrilMS]

@rymeskar - If you look at the TokenCacheNotificationArgs, you’ll see a cancellation token there. This is the cancellation token that was given via AcquireToken***.ExecuteAsync(cancellationToken).

I agree that it would have been better to have SetBeforeAccessAsync with a cancellationToken from the start. But we didn’t, so we had to add it later.

The reason why we didn’t add an overload for SetBeforeAccessAsync this is because the callback are part of an interface ITokenCache, and we can’t ADD a method to an interface. Note that since we still have to support .net classic, we can’t use default interface methods. Thoughts?