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Blazored / LocalStorage

A library to provide access to local storage in Blazor applications
https://blazored.github.io/LocalStorage/
MIT License
1.25k stars 117 forks source link

[Feature Request] Support Strongly Typed Serialization #211

Closed SGStino closed 2 months ago

SGStino commented 1 year ago

The current serialization model assumes JsonSerializer.Deserialize() will always work: (here)

    private async Task<ChangingEventArgs> RaiseOnChangingAsync(string key, object data)
    {
        var e = new ChangingEventArgs
        {
            Key = key,
            OldValue = await GetItemInternalAsync<object>(key).ConfigureAwait(false),
            NewValue = data
        };

        Changing?.Invoke(this, e);

        return e;
    }

This means that as soon as you use a JsonTypeInfoResolver that doesn't know what to do with object, like a source generated JsonSerializerContext, you essentially can't use the library anymore.

I'm not certain one could get away of making RaiseOnChangingAsync Generic, in most cases where the old value and the new value are of the same generic type, AND haven't changed over time, that would work.

But if one were to put different types in the same key, then that would certainly break. Where the old value is of OldType, the new of NewType: that would invoke RaiseOnChangingAsync<NewType>, which on its turn would invoke GetItemInternalAsync<NewType> instead of GetItemInternalAsync<OldType>, and you'd have a conflicting deserialization.

One could skip the entire ILocalStorageService and use IStorageProvider directly with custom, fixed, serialization, but the accessibility of internal interface IStorageProvider sadly doesn't allow that.

The alternative that remains is to use GetItemAsStringAsync, without a JsonSerializationContext on the library, and use a Serialization Context to generate the string. Which seems to work, but with a fair amount of overhead.

chrissainty commented 1 year ago

Hi @SGStino, could you provide a sample project showing the issue you're describing. I'm struggling to understand the issue based on the description.

SGStino commented 1 year ago

When using trimming and serialization, you can't deserialize , you need to specify the type, and the type needs to be known in the source generated serialization context.

chrissainty commented 1 year ago

I'll be honest, I'm not sure I understand what you're attempting to do. I haven't done any work whatsoever with source generators.

I think, for now at least, this is something you would need to handle in your own code and just use the GetItemAsStringAsync and SetItemAsStringAsync methods. I'd be happy to look at this again if there is a big demand for it.

SGStino commented 1 year ago

Well, the AsString functions are exactly what i'm using now in a custom service that wraps it and uses a DI injected context for the serializer.

Ps: if you want to know more about the source generation in System.Text.Json: https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json/source-generation?pivots=dotnet-8-0

MatthewSteeples commented 8 months ago

I think this is now supported thanks to some new APIs added to .NET 7/8. I've put the following in my program.cs file:

builder.Services.AddBlazoredLocalStorage(options => { options.JsonSerializerOptions.TypeInfoResolver = SerializationContext.Default; });

SerializationContext is what I've called my source generated JSON class

MatthewSteeples commented 8 months ago

OK, so I was a bit premature there. There's a small code path that isn't happy about enabling source generators. I'm going to see if I can put together a PR to fix it

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