CancellationTokenSource is not Disposed in cache tag helpers

[Funbit]

Inside https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNetCore.Mvc.TagHelpers/CacheTagHelper.cs#L80 (ProcessAsync method) there is a CancellationTokenSource instantiation without proper Dispose call.

Also, https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNetCore.Mvc.TagHelpers/DistributedCacheTagHelper.cs#L72 creates a new CancellationTokenSource which is not used anywhere.

I believe these places should be fixed.

[Eilon]

For https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNetCore.Mvc.TagHelpers/CacheTagHelper.cs#L80 I'm not sure what the intention is.

https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNetCore.Mvc.TagHelpers/DistributedCacheTagHelper.cs#L72 is definitely wrong - the CTS isn't even used, so we can just delete it.

@sebastienros can you take a look?

[Eilon]

@sebastienros - can you take a look to see if we need to do something here? Looks like there's at least a small change we need to make?

[sebastienros]

@Funbit

Based on our usage of the CancellationTokenSource there will be no Timer or callbacks registered, which means there is really nothing to dispose. There is also potentially a ManualResetEvent but I don't think it's initialized. So it should be safe in terms of memory management to not call Dispose.

My gut feeling would be to actually not call Dispose until it's proven that there is a memory leak from it, with our specific usage.