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

app/MindWork AI Studio/Chat/ChatDraft.cs

@@ -26,11 +26,16 @@ public sealed class ChatDraft
 {
     private readonly Lock stateLock = new();
 
+    //
+    // The setters are internal only for reading the JSON, since its source generation reaches no private
+    // setter. Everything else changes the draft through the methods below, which hold the lock.
+    //
+
     /// <summary>
     /// The text of the message.
     /// </summary>
     [JsonInclude]
-    public string Text { get; private set; } = string.Empty;
+    public string Text { get; internal set; } = string.Empty;
 
     /// <summary>
     /// The files attached to the message, the transcripts of audio and video files included.
@@ -40,7 +45,7 @@ public sealed class ChatDraft
     /// transcript is still a transcript after the chat was loaded again.
     /// </remarks>
     [JsonInclude]
-    public IReadOnlyList<FileAttachment> FileAttachments { get; private set; } = [];
+    public IReadOnlyList<FileAttachment> FileAttachments { get; internal set; } = [];
 
     /// <summary>
     /// The texts a preview read of the attached files, which sending takes along instead of reading the files again.
@@ -53,7 +58,7 @@ public sealed class ChatDraft
     /// store holds the texts themselves.
     /// </remarks>
     [JsonInclude]
-    public IReadOnlyList<PreviewedText> PreviewedTexts { get; private set; } = [];
+    public IReadOnlyList<PreviewedText> PreviewedTexts { get; internal set; } = [];
 
     /// <summary>
     /// Whether the draft holds neither text nor attachments.

app/MindWork AI Studio/Chat/ChatJsonContext.cs

@@ -0,0 +1,17 @@
+using System.Text.Json.Serialization;
+
+using ERIContentType = AIStudio.Tools.ERIClient.DataModel.ContentType;
+
+namespace AIStudio.Chat;
+
+/// <summary>
+/// The contracts with which System.Text.Json reads and writes chats, built at compile time.
+/// </summary>
+/// <remarks>
+/// Two types with the same name need a name of their own for their contract, else the generator builds
+/// only the first of them and warns with SYSLIB1031.
+/// </remarks>
+[JsonSourceGenerationOptions(GenerationMode = JsonSourceGenerationMode.Metadata)]
+[JsonSerializable(typeof(ChatThread))]
+[JsonSerializable(typeof(ERIContentType), TypeInfoPropertyName = "ERIContentType")]
+internal sealed partial class ChatJsonContext : JsonSerializerContext;

app/MindWork AI Studio/Chat/ChatThread.cs

@@ -23,7 +23,7 @@ public sealed record ChatThread
     /// <summary>
     /// The unique identifier of the chat thread.
     /// </summary>
-    public Guid ChatId { get; init; }
+    public Guid ChatId { get; set; }
     
     /// <summary>
     /// The unique identifier of the workspace.
@@ -42,16 +42,16 @@ public sealed record ChatThread
     /// Every copy of this thread made with a with expression shares the draft, because such a copy is
     /// still the same chat. A copy which becomes another chat needs a draft of its own.
     /// </remarks>
-    public ChatDraft Draft { get; init; } = new();
+    public ChatDraft Draft { get; set; } = new();
 
     // Compatibility shim: until v26.9.1, a chat stored only the transcripts of its draft, in a list of their own. See documentation/compatibility-shims/2026-10-chat-pending-media-transcripts.md; remove after 2027-04-11.
     [JsonInclude]
     [JsonPropertyName("pending_media_transcripts")]
     [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
-    private List<ManagedTranscriptAttachment>? LegacyPendingMediaTranscripts
+    internal List<ManagedTranscriptAttachment>? LegacyPendingMediaTranscripts
     {
         get => null;
-        init
+        set
         {
             if (value is not null)
                 this.Draft.AddAttachments(value);
@@ -127,7 +127,7 @@ public sealed record ChatThread
     /// continues it must meet the level.
     /// </summary>
     [JsonInclude]
-    public ConfidenceLevel RequiredProviderConfidence { get; private set; } = ConfidenceLevel.NONE;
+    public ConfidenceLevel RequiredProviderConfidence { get; internal set; } = ConfidenceLevel.NONE;
 
     public void RequireProviderConfidence(ConfidenceLevel minimumProviderConfidence)
     {
@@ -164,7 +164,7 @@ public sealed record ChatThread
     /// internal content demands nothing.
     /// </remarks>
     [JsonInclude]
-    public OutboundDataRequirement RequiredOutboundDataRestriction { get; private set; } = OutboundDataRequirement.NONE;
+    public OutboundDataRequirement RequiredOutboundDataRestriction { get; internal set; } = OutboundDataRequirement.NONE;
 
     /// <summary>
     /// Tightens where this chat may still send data to what the data brought in demands, and
@@ -229,7 +229,7 @@ public sealed record ChatThread
     /// immutable, so that a copy of the thread never shares a set which grows later.
     /// </remarks>
     [JsonInclude]
-    public ImmutableHashSet<string> WebAddressesWrittenByModels { get; private set; } = [];
+    public ImmutableHashSet<string> WebAddressesWrittenByModels { get; internal set; } = [];
 
     /// <summary>
     /// The name of the chat thread. Usually generated by an AI model or manually edited by the user.
@@ -244,7 +244,7 @@ public sealed record ChatThread
     /// <summary>
     /// The content blocks of the chat thread.
     /// </summary>
-    public List<ContentBlock> Blocks { get; init; } = [];
+    public List<ContentBlock> Blocks { get; set; } = [];
 
     /// <summary>
     /// The component running this thread, which decides the tools it may use and what its requests name.

app/MindWork AI Studio/Chat/ContentBlock.cs

@@ -8,12 +8,12 @@ public class ContentBlock
     /// <summary>
     /// Time when the content block was created.
     /// </summary>
-    public DateTimeOffset Time { get; init; }
+    public DateTimeOffset Time { get; set; }
     
     /// <summary>
     /// Type of the content block, e.g., text, image, voice, etc.
     /// </summary>
-    public ContentType ContentType { get; init; } = ContentType.NONE;
+    public ContentType ContentType { get; set; } = ContentType.NONE;
     
     /// <summary>
     /// The content of the block.
@@ -28,7 +28,7 @@ public class ContentBlock
     /// <summary>
     /// Should the content block be hidden from the user?
     /// </summary>
-    public bool HideFromUser { get; init; }
+    public bool HideFromUser { get; set; }
 
     public ContentBlock DeepClone(bool changeHideState = false, bool hideFromUser = true) => new()
     {

app/MindWork AI Studio/Chat/ContentImage.cs

@@ -58,7 +58,7 @@ public sealed class ContentImage : IContent, IImageSource
     /// <remarks>
     /// Is the image source a URL, a local file path, a base64 string, etc.?
     /// </remarks>
-    public required ContentImageSource SourceType { get; init; }
+    public required ContentImageSource SourceType { get; set; }
 
     /// <summary>
     /// The image source.

app/MindWork AI Studio/Chat/ContentPresentation.cs

@@ -33,10 +33,10 @@ public sealed class ContentPresentation
         }
     }
 
-    internal static ContentPresentation Create<T>(ContentPresentationKind kind, T data) => new()
+    internal static ContentPresentation Create<T>(ContentPresentationKind kind, T data, JsonSerializerOptions options) => new()
     {
         Kind = kind,
-        Data = JsonSerializer.SerializeToElement(data),
+        Data = JsonSerializer.SerializeToElement(data, options),
     };
 
     internal ContentPresentation DeepClone() => new()

app/MindWork AI Studio/Chat/FileAttachment.cs

@@ -15,8 +15,22 @@ namespace AIStudio.Chat;
 [JsonDerivedType(typeof(FileAttachment), typeDiscriminator: "file")]
 [JsonDerivedType(typeof(FileAttachmentImage), typeDiscriminator: "image")]
 [JsonDerivedType(typeof(ManagedTranscriptAttachment), typeDiscriminator: "managed_transcript")]
-public record FileAttachment(FileAttachmentType Type, string FileName, [property: JsonConverter(typeof(DataDirectoryRelativePathConverter))] string FilePath, long FileSizeBytes)
+public record FileAttachment(FileAttachmentType Type, string FileName, string FilePath, long FileSizeBytes)
 {
+    //
+    // The properties of the parameters, declared again to be settable. A derived attachment gets the type from
+    // its own constructor, and the source generation of System.Text.Json sets every init-only property while it
+    // creates the object, also one missing in the JSON, which would lose that type. Keep them first and in the
+    // order of the parameters, which is the order they get stored in:
+    //
+    public FileAttachmentType Type { get; set; } = Type;
+    public string FileName { get; set; } = FileName;
+
+    [JsonConverter(typeof(DataDirectoryRelativePathConverter))]
+    public string FilePath { get; set; } = FilePath;
+
+    public long FileSizeBytes { get; set; } = FileSizeBytes;
+
     /// <summary>
     /// Gets a value indicating whether the file type is forbidden and should not be attached.
     /// </summary>
@@ -69,7 +83,7 @@ public record FileAttachment(FileAttachmentType Type, string FileName, [property
     /// of chat templates, while null.
     /// </remarks>
     [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
-    public Guid? ProvenanceId { get; init; }
+    public Guid? ProvenanceId { get; set; }
 
     /// <summary>
     /// The state of the file which the stored text was read from, see ProvenanceId, or null while
@@ -80,7 +94,7 @@ public record FileAttachment(FileAttachmentType Type, string FileName, [property
     /// DataChat.ReadChangedAttachmentsAgain. Left out of the chat file while null.
     /// </remarks>
     [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
-    public FileVersion? Version { get; init; }
+    public FileVersion? Version { get; set; }
 
     /// <summary>
     /// Whether the file changed since its text was stored.

app/MindWork AI Studio/Chat/FileAttachmentImage.cs

@@ -10,7 +10,7 @@ public record FileAttachmentImage(string FileName, string FilePath, long FileSiz
     /// <remarks>
     /// Is the image source a URL, a local file path, a base64 string, etc.?
     /// </remarks>
-    public ContentImageSource SourceType { get; init; } = ContentImageSource.LOCAL_PATH;
+    public ContentImageSource SourceType { get; set; } = ContentImageSource.LOCAL_PATH;
 
     /// <summary>
     /// The image source.

app/MindWork AI Studio/Chat/IImageSource.cs

@@ -8,7 +8,7 @@ public interface IImageSource
     /// <remarks>
     /// Is the image source a URL, a local file path, a base64 string, etc.?
     /// </remarks>
-    public ContentImageSource SourceType { get; init; }
+    public ContentImageSource SourceType { get; set; }
 
     /// <summary>
     /// The image source.

app/MindWork AI Studio/Chat/ReportedTokenUsage.cs

@@ -20,7 +20,7 @@ public sealed record ReportedTokenUsage
     /// <summary>
     /// What everything sent to the model cost.
     /// </summary>
-    public int PromptTokens { get; init; }
+    public int PromptTokens { get; set; }
 
     /// <summary>
     /// Which model the number was charged for.
@@ -31,7 +31,7 @@ public sealed record ReportedTokenUsage
     /// being an answer about the request which is about to be sent, and the estimate, wrong as it
     /// is, is at least wrong about the right model.
     /// </remarks>
-    public string ModelId { get; init; } = string.Empty;
+    public string ModelId { get; set; } = string.Empty;
 
     /// <summary>
     /// How many blocks the conversation had when the request went out, this answer included.
@@ -45,7 +45,7 @@ public sealed record ReportedTokenUsage
     /// Taken when the request is sent rather than when the report arrives: whatever is deleted
     /// while the answer streams in was still part of what the provider counted.
     /// </remarks>
-    public int BlockCount { get; init; }
+    public int BlockCount { get; set; }
 
     /// <summary>
     /// States the stored number as a usage again.