Kareadita/Kavita · error · ArgumentException

Unsupported CBL file extension: {ext}

Error message

Unsupported CBL file extension: {ext}

What it means

Thrown by CblParser.Parse when the imported reading-list file has an extension other than .cbl, .xml (both routed to the V1 XML parser) or .json (V2 JSON parser). The parser does no content sniffing; the switch expression rejects anything else with an ArgumentException. This is a hard precondition failure: the file path's extension alone selects the deserializer.

Source

Thrown at Kavita.Services/Helpers/CblParser.cs:34

/// </summary>
public static class CblParser
{
    private static readonly JsonSerializerOptions JsonSerializerOptions = new JsonSerializerOptions()
    {
        PropertyNameCaseInsensitive = true,
    };

    /// <summary>
    /// Auto-detect format by file extension and parse accordingly.
    /// </summary>
    public static ParsedCblReadingList Parse(string filePath)
    {
        var ext = Path.GetExtension(filePath).ToLowerInvariant();
        return ext switch
        {
            ".cbl" or ".xml" => ParseV1(filePath),
            ".json" => ParseV2(filePath),
            _ => throw new ArgumentException($"Unsupported CBL file extension: {ext}")
        };
    }

    /// <summary>
    /// Parse a v1 XML CBL file into the unified model.
    /// </summary>
    public static ParsedCblReadingList ParseV1(string filePath)
    {
        var serializer = new XmlSerializer(typeof(CblReadingList));
        using var stream = File.OpenRead(filePath);
        var cbl = (CblReadingList)serializer.Deserialize(stream);

        var result = new ParsedCblReadingList
        {
            SchemaVersion = 1,
            Name = cbl.Name ?? string.Empty,
            Summary = cbl.Summary ?? string.Empty,
            StartYear = cbl.StartYear,

View on GitHub (pinned to 9c3e540000)

Solutions

1. Re-save/rename the file so its extension is exactly .cbl, .xml, or .json before uploading.
2. Confirm the V1 (XML) vs V2 (JSON) schema of the contents, then pick the matching extension — .cbl/.xml for the XML format, .json for the V2 format.
3. If you control the pipeline, strip leading/trailing whitespace and any accidental double dots from the filename upstream of Parse.
4. If a new format is legitimately needed, extend the switch in CblParser.Parse with a new arm and a ParseV* method.

Example fix

// before
var result = CblParser.Parse("readinglist.cbz");

// after
var result = CblParser.Parse(Path.ChangeExtension("readinglist.cbz", ".cbl"));

private static readonly HashSet<string> AllowedCblExtensions = new(StringComparer.OrdinalIgnoreCase) { ".cbl", ".xml", ".json" };

bool IsValidCblFile(string path)
{
    var ext = Path.GetExtension(path);
    return !string.IsNullOrEmpty(ext) && AllowedCblExtensions.Contains(ext);
}

// before upload
if (!IsValidCblFile(upload.FileName)) return BadRequest("Only .cbl, .xml, .json are accepted.");

bool IsCblParseable(string path) =>
    Path.GetExtension(path)?.ToLowerInvariant() is ".cbl" or ".xml" or ".json";

try { var list = CblParser.Parse(path); }
catch (ArgumentException ex) when (ex.Message.StartsWith("Unsupported CBL file extension"))
{ /* surface 'unsupported file type' to user */ }

When it happens

Trigger: Calling CblParser.Parse(filePath) where Path.GetExtension(filePath).ToLowerInvariant() returns something not in {".cbl", ".xml", ".json"}. Triggered via the CBL import endpoint when a user uploads a .cbz, .txt, .zip, a file with no extension, or a case the ToLowerInvariant did not normalize away from the allowed set.

Common situations: User uploads a ComicBookLover .cbz or a .cbl.txt that an OS/mail client renamed; file saved with a trailing dot or hidden double extension (".json " with whitespace, ".JSON" is fine but ".Json.bak" is not); a reading-list export from another tool uses a proprietary extension.

Related errors

• reading-list-restricted

AI-assisted analysis of Kareadita/Kavita@9c3e540000 (2026-08-13). Data as JSON: /api/errors/0164254f27341b9e. Report an issue: GitHub.