Generated the JSON contracts of the stored data at compile time (#1148)

app/Tests/Serialization/JsonReflectionBaseline.cs

@@ -0,0 +1,27 @@
+using System.Runtime.CompilerServices;
+using System.Text.Json;
+using System.Text.Json.Serialization.Metadata;
+
+namespace AIStudio.Tests.Serialization;
+
+/// <summary>
+/// The options of AI Studio as System.Text.Json uses them without source generation: the same settings, but
+/// with contracts which reflection builds.
+/// </summary>
+/// <remarks>
+/// AI Studio stored all its files with such contracts, so they are the baseline every other contract has to
+/// match. Each baseline is built once per options, since reflection builds its contracts once per options, too.
+/// </remarks>
+public static class JsonReflectionBaseline
+{
+    private static readonly ConditionalWeakTable<JsonSerializerOptions, JsonSerializerOptions> BASELINES = new();
+
+    /// <summary>
+    /// Returns a copy of the given options, whose contracts reflection builds.
+    /// </summary>
+    /// <param name="options">The options AI Studio uses.</param>
+    public static JsonSerializerOptions Of(JsonSerializerOptions options) => BASELINES.GetValue(options, static original => new JsonSerializerOptions(original)
+    {
+        TypeInfoResolver = new DefaultJsonTypeInfoResolver(),
+    });
+}