git-ecosystem/git-credential-manager · error · ArgumentException

Argument cannot be empty or white space.

Error message

Argument cannot be empty or white space.

What it means

This ArgumentException is thrown by EnsureArgument.NotNullOrWhiteSpace when a required string argument is null, empty, or contains only whitespace. The library treats empty/whitespace strings as invalid because downstream code depends on a meaningful value. The parameter name is passed to ArgumentException so the caller can identify the offending argument.

Solutions

1. Ensure the string argument is non-empty and contains at least one non-whitespace character before calling the API that validates it
2. Check the source of the value (config file, env var, user input) and fix the upstream producer that yields an empty/whitespace value
3. If null is the issue, note the message comes from NotNull first; supply an actual string object
4. Add validation or defaults at application startup so blank values fail early with a clearer message

Example fix

// before
EnsureArgument.NotNullOrWhiteSpace(apiKey, nameof(apiKey)); // throws when apiKey = "   "
// after
if (string.IsNullOrWhiteSpace(apiKey))
    throw new InvalidOperationException("apiKey must be configured; set API_KEY env var");
EnsureArgument.NotNullOrWhiteSpace(apiKey, nameof(apiKey));

public static bool IsValidNonWhiteSpace(string s) => !string.IsNullOrWhiteSpace(s);
// usage: if (!IsValidNonWhiteSpace(apiKey)) throw new InvalidOperationException("apiKey required");

static bool HasValue(string? s) => !string.IsNullOrWhiteSpace(s);

try { EnsureArgument.NotNullOrWhiteSpace(value, nameof(value)); }
catch (ArgumentException ex) when (ex.ParamName == nameof(value))
{
    logger.LogWarning("Value for {Param} was empty; using default", ex.ParamName);
    value = defaultValue;
}

When it happens

Trigger: Calling EnsureArgument.NotNullOrWhiteSpace(arg, name) when arg is null, "", or consists only of spaces/tabs/newlines. Note NotNull(arg, name) runs first, so a null arg throws ArgumentNullException from NotNull rather than this message.

Common situations: Passing an unset environment variable or empty config value as an API key, host, or connection string; trimming user input to an empty string; a deserialized object with a blank required field.

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

• Must specify at least one AuthenticationModes
• Argument must be an absolute URI.
• Argument must be positive or zero (non-negative).
• Argument must be positive.
• Argument must be negative or zero (non-positive).

AI-assisted analysis of git-ecosystem/git-credential-manager@e8ce762cd0 (2026-09-11). Data as JSON: /api/errors/61447dd3e6ef8237. Report an issue: GitHub.

Appendix: source

Thrown at src/Core/EnsureArgument.cs:31

        }

        public static void NotNullOrEmpty(string arg, string name)
        {
            NotNull(arg, name);

            if (string.IsNullOrEmpty(arg))
            {
                throw new ArgumentException("Argument cannot be empty.", name);
            }
        }

        public static void NotNullOrWhiteSpace(string arg, string name)
        {
            NotNull(arg, name);

            if (string.IsNullOrWhiteSpace(arg))
            {
                throw new ArgumentException("Argument cannot be empty or white space.", name);
            }
        }

        public static void AbsoluteUri(Uri arg, string name)
        {
            NotNull(arg, name);

            if (!arg.IsAbsoluteUri)
            {
                throw new ArgumentException("Argument must be an absolute URI.", name);
            }
        }

        public static void PositiveOrZero(int arg, string name)
        {
            if (arg < 0)
            {
                throw new ArgumentOutOfRangeException(name, "Argument must be positive or zero (non-negative).");

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