spectreconsole/spectre.console · error · ArgumentException

Task name cannot be empty

Error message

Task name cannot be empty

What it means

Thrown by the ProgressTask constructor when the description parameter, after RemoveNewLines and Trim, is null or whitespace. The null check on description itself throws ArgumentNullException separately; this ArgumentException fires when description is a non-null string that becomes empty after trimming (e.g., " ", "\n\t", or ""). Every ProgressTask must have a visible, non-empty description for rendering.

Source

Thrown at src/Spectre.Console/Live/Progress/ProgressTask.cs:142

    /// </summary>
    /// <param name="id">The task ID.</param>
    /// <param name="description">The task description.</param>
    /// <param name="maxValue">The task max value.</param>
    /// <param name="autoStart">Whether or not the task should start automatically.</param>
    /// <param name="timeProvider">The time provider to use. Defaults to <see cref="TimeProvider.System"/>.</param>
    public ProgressTask(int id, string description, double maxValue, bool autoStart = true, TimeProvider? timeProvider = null)
    {
        lazySamples = new(() => new CircularBuffer<ProgressSample>(MaxSamplesKept) { UniqueRemovedCheck = false });
        _lock = new object();
        _timeProvider = timeProvider ?? TimeProvider.System;
        _maxValue = maxValue;
        _value = 0;
        _description = description?.RemoveNewLines()?.Trim() ??
                       throw new ArgumentNullException(nameof(description));

        if (string.IsNullOrWhiteSpace(_description))
        {
            throw new ArgumentException("Task name cannot be empty", nameof(description));
        }

        Id = id;
        State = new ProgressTaskState();
        StartTime = autoStart ? _timeProvider.GetLocalNow().LocalDateTime : null;
    }

    /// <summary>
    /// Starts the task.
    /// </summary>
    public void StartTask()
    {
        lock (_lock)
        {
            if (StopTime != null)
            {
                throw new InvalidOperationException("Stopped tasks cannot be restarted");
            }

View on GitHub (pinned to 0acc92fada)

Solutions

1. Validate the description string is non-whitespace before constructing the ProgressTask or calling AddTask.
2. Provide a fallback description when the source data is empty: var desc = string.IsNullOrWhiteSpace(name) ? "Unnamed task" : name;
3. Sanitize input upstream so empty descriptions never reach the progress API.

Example fix

// before
var task = ctx.AddTask(userInput); // userInput may be "   "

// after
var desc = string.IsNullOrWhiteSpace(userInput) ? "Processing" : userInput;
var task = ctx.AddTask(desc);

// Sanitize description before creating task
var desc = string.IsNullOrWhiteSpace(description)
    ? "Unnamed task"
    : description.Trim();
var task = new ProgressTask(id, desc, maxValue);

static bool IsValidTaskDescription(string? description)
    => !string.IsNullOrWhiteSpace(description);

When it happens

Trigger: Creating new ProgressTask(id, " ", 100) or new ProgressTask(id, "", 100); also new ProgressTask(id, "\n\n", 100). Calling AnsiConsole.Progress().Start(ctx => ctx.AddTask(" ")) hits this same constructor.

Common situations: Description sourced from user input, config, or data that wasn't validated for whitespace; dynamically generated names from data that produces empty strings; copy-paste leaving a placeholder empty string in AddTask.

Related errors

• Task name cannot be empty.
• Stopped tasks cannot be restarted
• Array does not contain enough space for items
• At least one column must be specified.
• Invalid Figlet font

AI-assisted analysis of spectreconsole/spectre.console@0acc92fada (2026-08-13). Data as JSON: /api/errors/41b38c531e6d0f80. Report an issue: GitHub.