microsoft/aspire · error · ArgumentException

Launch arguments must contain at least one entry.

Error message

Launch arguments must contain at least one entry.

What it means

ProjectLaunchArgsOverrideAnnotation.ValidateArguments rejects an empty arguments list. An override annotation that replaced launch arguments with an empty set is almost certainly a mistake — the project would be started with no arguments at all — so the annotation fails fast.

Solutions

1. Supply at least one launch argument, e.g. new ProjectLaunchArgsOverrideAnnotation(["run"]...)
2. Guard before constructing: if (args.Count == 0) args = ["run"];
3. If no override is needed, don't add the annotation instead of passing an empty list

Example fix

// before
var annotation = new ProjectLaunchArgsOverrideAnnotation(filteredArgs); // filteredArgs == []
// after
var annotation = filteredArgs.Count > 0
    ? new ProjectLaunchArgsOverrideAnnotation(filteredArgs)
    : new ProjectLaunchArgsOverrideAnnotation(["run"]);

if (args.Count == 0) args = ["run"]; // or skip adding the annotation
var annotation = new ProjectLaunchArgsOverrideAnnotation(args);

try { new ProjectLaunchArgsOverrideAnnotation(args); } catch (ArgumentException) { /* fall back to no override */ }

When it happens

Trigger: new ProjectLaunchArgsOverrideAnnotation(Array.Empty<string>()) or passing a filtered/derived list that ended up empty to the annotation constructor.

Common situations: Building the argument list by filtering user-supplied args where none matched; passing an uninitialized array; removing the leading resource argument and then assigning the now-empty remainder.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• The leading resource argument to remove cannot be empty.
• At least one process command success exit code must be…
• Object must implement IManifestExpressionProvider
• Object must implement IValueProvider
• Resource ' ' cannot produce a " " launch configuration…

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/5eb3f3d8695961ec. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting/ApplicationModel/ProjectLaunchArgsOverrideAnnotation.cs:66

    internal void Apply(IList<string> projectArgs, string projectPath, string? configuration)
    {
        projectArgs.AddRange(Arguments);
        projectArgs.Add(projectPath);

        if (!string.IsNullOrEmpty(configuration))
        {
            projectArgs.AddRange(["--configuration", configuration]);
        }
    }

    private static IReadOnlyList<string> ValidateArguments(IReadOnlyList<string> arguments)
    {
        ArgumentNullException.ThrowIfNull(arguments);

        if (arguments.Count == 0)
        {
            throw new ArgumentException("Launch arguments must contain at least one entry.", nameof(arguments));
        }

        return arguments;
    }

    private static string? ValidateLeadingResourceArgumentToRemove(string? leadingResourceArgumentToRemove)
    {
        if (leadingResourceArgumentToRemove is not null && leadingResourceArgumentToRemove.Length == 0)
        {
            throw new ArgumentException("The leading resource argument to remove cannot be empty.", nameof(leadingResourceArgumentToRemove));
        }

        return leadingResourceArgumentToRemove;
    }
}

View on GitHub (pinned to 25830f84bd)