bchavez/Bogus · error · ArgumentException

The method call '{methodCall}' is missing a terminating ')'

Error message

The method call '{methodCall}' is missing a terminating ')' character.

What it means

Thrown by Tokenizer.GetArgumentsString (Tokenizer.cs:176). Once ParseMustashText sees an opening '(' it enters argument mode and asks GetArgumentsString for the text up to the first ')'. If no ')' exists in the call text it throws ArgumentException. The tokenizer found an argument list opener but the call never closes.

Source

Thrown at Source/Bogus/Tokenizer.cs:176

   }

   private static object GetValueForParameter(ParameterInfo parameterInfo, string parameterValue)
   {
      var type = Nullable.GetUnderlyingType(parameterInfo.ParameterType) ?? parameterInfo.ParameterType;

      if( typeof(Enum).IsAssignableFrom(type)) return Enum.Parse(type, parameterValue);

      if( typeof(TimeSpan) == type ) return TimeSpan.Parse(parameterValue);

      return Convert.ChangeType(parameterValue, type);
   }

   private static string GetArgumentsString(string methodCall, int parametersStart)
   {
      var parametersEnd = methodCall.IndexOf(')');
      if( parametersEnd == -1 )
      {
         throw new ArgumentException($"The method call '{methodCall}' is missing a terminating ')' character.");
      }

      return methodCall.Substring(parametersStart + 1, parametersEnd - parametersStart - 1);
   }
}

[AttributeUsage(AttributeTargets.Property)]
internal class RegisterMustasheMethodsAttribute : Attribute;

View on GitHub (pinned to 6ece18c5c2)

Solutions

Ensure every {{category.method(...)}} has a ')' before the closing '}}'.
Run a paren-balance/shape check on the template before parsing.
If you don't need arguments, omit the parentheses entirely: {{random.number}} selects the 0-arg overload and never enters argument mode.

Example fix

// before
faker.Parse("{{random.number(5}}");
// after
faker.Parse("{{random.number(5,100)}}");

Defensive patterns

Strategy: validation

Validate before calling

// Verify every token that opens '(' also closes ')' before the '}}'.
static bool TemplatesWellFormed(string tpl)
{
    foreach (Match m in Regex.Matches(tpl, @"\{\{(.*?)\}\}"))
    {
        var body = m.Groups[1].Value;
        if (body.Contains('(') && !body.Contains(')')) return false;
    }
    return true;
}

Try / catch

try { var s = faker.Parse(tpl); }
catch (ArgumentException ex) when (ex.Message.Contains("missing a terminating ')'"))
{
    throw new InvalidOperationException($"Malformed handlebar (no closing paren) in template: {tpl}", ex);
}

Prevention

For no-argument calls, drop the parentheses: {{random.number}} is valid and avoids this path entirely.
Add a unit test that parses every template constant at startup to catch truncation early.
Watch for config/templating layers that strip trailing punctuation and silently eat ')'.

When it happens

Trigger: A token with '(' but no matching ')': {{random.number(5}} (forgot the paren), {{name.lastname(}}, or a copy-paste that dropped the closing characters. Because the parser locates the outer '}}' first with IndexOf, any stray content can consume the intended ')'.

Common situations: Hand-authoring templates; a templating/config layer that strips trailing punctuation and silently removes ')'; nested/malformed handlebars where '}}' appears before the intended ')'.

Related errors

AI-assisted analysis of bchavez/Bogus@6ece18c5c2 (2026-08-13). Data as JSON: /api/errors/d927149bbb30aa9b. Report an issue: GitHub.