[API Proposal]: HybridCache - make it easier to use custom JsonSerializerOptions

[tyler-boyd]

Background and motivation

The default HybridCache serializer uses JsonSerializer, but there is no way to configure the JsonSerializerOptions.

I think it is fairly common to have a custom JsonSerializerOptions which is helpful (or even necessary) for serializing cached types. Thus I think it would be helpful if it were easier to configure the JsonSerializerOptions used by the HybridCache.

As it stands now, you have to write your own serializer factory which is a lot of boilerplate.

API Proposal

In general I see 2 main options:

1. The DefaultJsonSerializerFactory tries to obtain a JsonSerializerOptions from the DI container (no API change)
2. The DefaultJsonSerializerFactory is made public, taking a JsonSerializerOptions parameter, so we can use it with .AddSerializerFactory(...) instead of re-implementing it

API Usage

For option 1, there's no change, you'd just need to add a singleton JsonSerializerOptions to DI

For option 2, it would look something like this:

var jsonSerializerOptions = BuildJsonSerializerOptions();
services.AddHybridCache(opts =>
{
    opts.DefaultEntryOptions = new HybridCacheEntryOptions { Expiration = TimeSpan.FromMinutes(5) };
}).AddSerializerFactory(new DefaultJsonSerializerFactory(jsonSerializerOptions));

Alternative Designs

No response

Risks

Option 1 could be considered a breaking change since the JSON serialization behaviour would change, however the hybrid cache is still experimental. Option 2 should not break anything.

[mgravell]

I was thinking of this in the context of protobuf the other day; the option I arrived at was similar, but using keyed-DI to make sure that we're talking about the correct options, which can be summarized as:

    /// <summary>
    /// Register a specific serializer instance to use for <see cref="HybridCache"/> serialization.
    /// </summary>
    public static IServiceCollection AddProtobufNetHybridCachModel(this IServiceCollection services, TypeModel model)
    {
        services.AddKeyedSingleton<TypeModel>(typeof(HybridCache), model);
        return services;
    }
...
     public ProtoHybridCacheSerializerFactory([FromKeyedServices(typeof(HybridCache))] TypeModel? model = null)

This seems to work, and potentially allows it to be configured today without an API change, with a new API to do the same in .NET 10

(example from protobuf-net)

So: suggestion - for now, we allow services.AddKeyedSingleton<JsonSerializerOptions>(typeof(HybridCache), yourValueHere);

[tyler-boyd]

Yeah, I think that solution would work very nicely! Using the type as the key is a pretty creative way to do it.

[mgravell]

see linked PR