microsoft/aspire · error · ArgumentException

The leading resource argument to remove cannot be empty.

Error message

The leading resource argument to remove cannot be empty.

What it means

ValidateLeadingResourceArgumentToRemove permits null (no removal) but rejects the empty string. An empty value would be interpreted as 'remove the first empty argument', which is meaningless, so it is treated as an invalid argument rather than 'no removal'.

Solutions

Pass null to indicate no removal instead of ""
Normalize: leadingArg.Length == 0 ? null : leadingArg before assigning
Fix the source (env var / config) that supplies an empty string

Example fix

// before
var annotation = new ProjectLaunchArgsOverrideAnnotation(args, leadingArg: envValue ?? "");
// after
var annotation = new ProjectLaunchArgsOverrideAnnotation(args, leadingArg: string.IsNullOrEmpty(envValue) ? null : envValue);

Defensive patterns

Strategy: validation

Validate before calling

leadingArg = string.IsNullOrEmpty(leadingArg) ? null : leadingArg;

Try / catch

try { new ProjectLaunchArgsOverrideAnnotation(args, leadingArg); } catch (ArgumentException) { /* normalize empty to null and retry */ }

Prevention

Normalize empty strings to null for optional values
Never split/conflate 'missing' and 'empty' config inputs

When it happens

Trigger: Passing "" as LeadingResourceArgumentToRemove to the ProjectLaunchArgsOverrideAnnotation constructor or property setter; deriving the value from a substring/split operation that returned empty.

Common situations: A config value or CLI arg was present but empty (e.g. LEADING_ARG=""); splitting an argument string that produced an empty first token; translating a nullable source where empty and missing were conflated.

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

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/0e4bf62af9edff10. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting/ApplicationModel/ProjectLaunchArgsOverrideAnnotation.cs:76

    }

    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)