mgth/LittleBigMouse · error · JsonException

Unterminated border resistance side.

Error message

Unterminated border resistance side.

What it means

After reading the initial token, Read loops through the object's members until it encounters EndObject. If the JSON stream ends (Read returns false) before the closing brace of the border-resistance-side object, the converter throws this JsonException. It indicates the serialized object was never closed.

Solutions

1. Validate the JSON file with a parser (e.g. JSON lint) and add the missing closing braces.
2. Restore the settings file from backup or delete it so the app recreates defaults.
3. Enable atomic writes (write temp file then rename) in whatever code persists these settings to avoid truncation.
4. Catch JsonException during load and fall back to a freshly generated default config.

Example fix

// before (truncated)
{ "left": { "resistance": 5
// after
{ "left": { "resistance": 5 } }

// verify JSON is well-formed before deserializing
try { using var _ = System.Text.Json.JsonDocument.Parse(json); }
catch (JsonException) { json = "{}"; /* rebuild defaults */ }

static bool IsCompleteJson(string s)
{
    try { using var _ = System.Text.Json.JsonDocument.Parse(s); return true; }
    catch (JsonException) { return false; }
}

try
{
    dto = JsonSerializer.Deserialize<BorderSideDto>(json, options);
}
catch (JsonException ex) when (ex.Message.Contains("Unterminated"))
{
    Log.LogWarning("Settings JSON truncated; regenerating defaults.");
    dto = new BorderSideDto();
}

When it happens

Trigger: Deserializing truncated JSON such as {"left": {"resistance": 5 with no closing braces, typically from a partially written or cut-off settings file.

Common situations: Settings file corrupted by an app crash or power loss mid-write, file truncated by sync/disk issues, or manual editing that dropped closing braces.

Understand the failure class

Background: JSON parse error: "Unexpected token" / "not valid JSON" / "failed to parse" — what JSON parsers are really complaining about — this error's family across 45 libraries.

Related errors

• Unexpected token for a border resistance side.

AI-assisted analysis of mgth/LittleBigMouse@7a42f01d47 (2026-09-16). Data as JSON: /api/errors/e31ec4c4235bf139. Report an issue: GitHub.

Appendix: source

Thrown at LittleBigMouse.Plugins/LittleBigMouse.Plugins.Core/Persistence/BorderSideDtoJsonConverter.cs:79

                case nameof(BorderSideDto.MoveBlock):
                    dto.MoveBlock = ReadNullableBool(ref reader);
                    break;
                case nameof(BorderSideDto.Drag):
                    dto.Drag = ReadNullableDouble(ref reader);
                    break;
                case nameof(BorderSideDto.DragBlock):
                    dto.DragBlock = ReadNullableBool(ref reader);
                    break;
                case nameof(BorderSideDto.Sections):
                    dto.Sections = JsonSerializer.Deserialize<List<BorderSectionDto>>(ref reader, options);
                    break;
                default:
                    reader.Skip();
                    break;
            }
        }

        throw new JsonException("Unterminated border resistance side.");
    }

    public override void Write(Utf8JsonWriter writer, BorderSideDto value, JsonSerializerOptions options)
    {
        writer.WriteStartObject();

        if (value.Move is { } move) writer.WriteNumber(nameof(BorderSideDto.Move), move);
        if (value.MoveBlock is { } moveBlock) writer.WriteBoolean(nameof(BorderSideDto.MoveBlock), moveBlock);
        if (value.Drag is { } drag) writer.WriteNumber(nameof(BorderSideDto.Drag), drag);
        if (value.DragBlock is { } dragBlock) writer.WriteBoolean(nameof(BorderSideDto.DragBlock), dragBlock);

        if (value.Sections is { Count: > 0 } sections)
        {
            writer.WritePropertyName(nameof(BorderSideDto.Sections));
            JsonSerializer.Serialize(writer, sections, options);
        }

        writer.WriteEndObject();

View on GitHub (pinned to 7a42f01d47)