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[API Proposal]: Expose a JsonSerializerOptions.Default property #61093
Description
Background and motivation
JsonSerializerOptions currently exposes an internal s_defaultOptions instance for use by System.Text.Json. This is useful since JsonSerializerOptions holds the reflection-based serialization metadata cache, as such creating a default new JsonSerializerOptions() instance can be very expensive since it forces the regeneration of that cache.
I propose we make this singleton a public property so that users can read default configuration cheaply (e.g. the default JsonConverter for a requested type).
API Proposal
namespace System.Text.Json
{
public partial class JsonSerializerOptions
{
public static JsonSerializerOptions Default { get; }
}
}API Usage
Here's an (artificial) example of how the property can be used to cheaply recover the default converter used by STJ for integers:
public class MyCustomConverter : JsonConverter<int>
{
private readonly static JsonConverter<int> s_defaultConverter = (JsonConverter<int>)JsonSerializerOptions.Default.GetConverter(typeof(int));
// custom serialization logic
public override void Write(Utf8JsonWriter writer, int value, JsonSerializerOptions options)
{
return writer.WriteStringValue(value.ToString());
}
// fall back to default deserialization logic
public override int Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
{
return s_defaultConverter.Read(ref reader, typeToConvert, options);
}
}Alternative Designs
No response
Risks
No response
Activity
TonyValenti commentedon Nov 2, 2021
Would the defaults be mutable? My recommendation is "No".
eiriktsarpalis commentedon Nov 2, 2021
It would not be. Moreover the implementation of this property would need to make sure that the instance is locked for modification before being returned.
terrajobst commentedon Nov 2, 2021
Video