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

app/Tests/Serialization/JsonCoverageTests.cs

@@ -0,0 +1,25 @@
+using System.Text.Json.Serialization;
+
+namespace AIStudio.Tests.Serialization;
+
+/// <summary>
+/// Checks that every contract AI Studio uses for its JSON comes from source generation, never from reflection.
+/// </summary>
+/// <remarks>
+/// A type which no context of the options knows makes System.Text.Json throw, unless the options fall back to
+/// reflection. Such a fallback hides the missing type until a trimmed build removes what reflection needs, and
+/// only a published build shows it then.
+/// </remarks>
+[TestFixture]
+public sealed class JsonCoverageTests
+{
+    [TestCaseSource(typeof(JsonTestRoots), nameof(JsonTestRoots.Stored))]
+    public void EveryContractComesFromSourceGeneration(JsonTestRoot root)
+    {
+        var typesWithoutGeneratedContract = JsonTypeGraph.Collect(root.Type, root.Options)
+            .Where(type => root.Options.GetTypeInfo(type).OriginatingResolver is not JsonSerializerContext)
+            .Select(JsonContractDescription.TypeName);
+
+        Assert.That(typesWithoutGeneratedContract, Is.Empty);
+    }
+}