Refused JSON contracts built by reflection and checked all of them in the trimmed build (#1152)

app/TrimSmokeTest/AppJsonOptions.cs

@@ -0,0 +1,60 @@
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace AIStudio.TrimSmokeTest;
+
+/// <summary>
+/// Finds the options with which AI Studio reads and writes JSON.
+/// </summary>
+/// <remarks>
+/// AI Studio keeps each kind of options in a static field or property, next to the code which uses them, so
+/// these are the options which reach System.Text.Json. A list written by hand would miss the next new one.
+/// The tests of the app compile this file, too, see Tests.csproj, so that both check the same options.
+/// </remarks>
+public static class AppJsonOptions
+{
+    private const BindingFlags STATIC_MEMBERS = BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.DeclaredOnly;
+
+    /// <summary>
+    /// Returns the options of every static field and property of AI Studio which holds some.
+    /// </summary>
+    /// <remarks>
+    /// Reading a member runs the type initializer of its type. Hence, the static state which the start of
+    /// the app fills has to be there before, Program.LOGGER_FACTORY above all.
+    /// </remarks>
+    /// <returns>The options by the name of their type and member, e.g., SettingsManager.JSON_OPTIONS.</returns>
+    public static IReadOnlyDictionary<string, JsonSerializerOptions> FindAll()
+    {
+        var found = new SortedDictionary<string, JsonSerializerOptions>(StringComparer.Ordinal);
+
+        //
+        // The Program of AI Studio, not the one of the trim smoke test, which is closer from here. Only within
+        // the tests, which compile this file, too, the qualifier is redundant, and Rider reads it there:
+        //
+        // ReSharper disable once RedundantNameQualifier
+        foreach (var type in typeof(AIStudio.Program).Assembly.GetTypes())
+        {
+            //
+            // A context keeps options of its own for its Default instance, which never reach System.Text.Json
+            // directly. The static members of an open generic type hold no value at all:
+            //
+            if (type.ContainsGenericParameters || type.IsSubclassOf(typeof(JsonSerializerContext)))
+                continue;
+
+            //
+            // The field behind a static auto-property is found as the property already:
+            //
+            foreach (var field in type.GetFields(STATIC_MEMBERS))
+                if (field.FieldType == typeof(JsonSerializerOptions) && !field.IsDefined(typeof(CompilerGeneratedAttribute)) && field.GetValue(null) is JsonSerializerOptions options)
+                    found.Add($"{type.Name}.{field.Name}", options);
+
+            foreach (var property in type.GetProperties(STATIC_MEMBERS))
+                if (property.PropertyType == typeof(JsonSerializerOptions) && property.GetMethod is not null && property.GetValue(null) is JsonSerializerOptions options)
+                    found.Add($"{type.Name}.{property.Name}", options);
+        }
+
+        return found;
+    }
+}