Adopted further C# 14 and .NET 10 features (#1158)

app/Tests/Serialization/DuplicatePropertyTests.cs

@@ -0,0 +1,67 @@
+using System.Text.Json;
+
+using AIStudio.Assistants.Builder;
+using AIStudio.Assistants.VisualBriefing;
+using AIStudio.Tools.ERIClient;
+using AIStudio.Tools.ERIClient.DataModel;
+
+namespace AIStudio.Tests.Serialization;
+
+/// <summary>
+/// Checks that JSON which a model or a server wrote may name a field only once.
+/// </summary>
+/// <remarks>
+/// JSON allows a name twice, and readers disagree on which of the values counts. Whatever AI Studio
+/// checks in such an answer, another reader may see the other value, so these options refuse it. The
+/// stored data, such as the settings, stays out of this: AI Studio wrote it itself, and refusing it
+/// would lose it.
+/// </remarks>
+[TestFixture]
+public sealed class DuplicatePropertyTests
+{
+    private static IEnumerable<TestCaseData> OptionsForAnswersFromOutside()
+    {
+        yield return new TestCaseData(LuaResponse.JSON_OPTIONS).SetName("The plugins the Assistant Builder writes");
+        yield return new TestCaseData(LauncherTextsResponse.JSON_OPTIONS).SetName("The texts the Assistant Builder writes for a chat launcher");
+        yield return new TestCaseData(VisualBriefingJson.Canonical).SetName("The answers of the model for a visual briefing");
+        yield return new TestCaseData(ERIClientBase.JSON_OPTIONS).SetName("The answers of ERI servers");
+    }
+
+    [TestCaseSource(nameof(OptionsForAnswersFromOutside))]
+    public void TheOptionsRefuseAFieldNamedTwice(JsonSerializerOptions options) => Assert.That(options.AllowDuplicateProperties, Is.False);
+
+    [Test]
+    public void APluginWhoseLuaCodeIsNamedTwiceIsRefused()
+    {
+        var isParsed = LuaResponse.TryParse("""{"full_lua":"ID = \"a\"","full_lua":"ID = \"b\""}""", out _, out var error, out var technicalDetails);
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(isParsed, Is.False);
+            Assert.That(error, Is.EqualTo(LuaResponseParseError.INVALID_JSON));
+            Assert.That(technicalDetails, Does.Contain("'full_lua'"), "The user learns which field the model wrote twice.");
+        }
+    }
+
+    [Test]
+    public void TextsForAChatLauncherWithATitleNamedTwiceAreRefused()
+    {
+        var isParsed = LauncherTextsResponse.TryParse("""{"title":"Budget","title":"Travel"}""", out _, out var error, out var technicalDetails);
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(isParsed, Is.False);
+            Assert.That(error, Is.EqualTo(LuaResponseParseError.INVALID_JSON));
+            Assert.That(technicalDetails, Does.Contain("'title'"), "The user learns which field the model wrote twice.");
+        }
+    }
+
+    [TestCase("""{"allowedProviderType":"SELF_HOSTED","allowedProviderType":"ANY"}""", TestName = "The same name twice")]
+    [TestCase("""{"allowedProviderType":"SELF_HOSTED","AllowedProviderType":"ANY"}""", TestName = "Two names which differ only in case")]
+    public void SecurityRequirementsOfAnERIServerWhichNameAFieldTwiceAreRefused(string answer)
+    {
+        var exception = Assert.Throws<JsonException>(() => JsonSerializer.Deserialize<SecurityRequirements>(answer, ERIClientBase.JSON_OPTIONS));
+
+        Assert.That(exception.Message, Does.Contain("AllowedProviderType").IgnoreCase, "The message names the field the server wrote twice.");
+    }
+}