Unity-Technologies/UnityCsReference · error · Exception

Id must be a number (line: '{line}')

Error message

Id must be a number (line: '{line}')

What it means

Thrown when the rule id (the text after ':' up to the first '|') cannot be parsed as an Int32. Restricted API rule ids must be numeric so they can be used as dictionary keys and for override matching.

Source

Thrown at Editor/Mono/Scripting/RestrictedApisValidation/RestrictedApisConfig.cs:177

        var signature = NextToken(ref lineSpan, out separatorIndex);
        if (separatorIndex == -1)
            throw new Exception($"Invalid severity '' in line '{line}'");

        var severitySpan = NextToken(ref lineSpan, out separatorIndex);
        var description = "";
        var documentationUrl = "";
        if (separatorIndex != -1)
        {
            description = NextToken(ref lineSpan,  out separatorIndex).ToString();
            if (separatorIndex != -1)
            {
                documentationUrl = NextToken(ref lineSpan,  out separatorIndex).ToString();
            }
        }

        if (!Int32.TryParse(id, out var intId))
        {
            throw new Exception($"Id must be a number (line: '{line}')");
        }

        int referenceHashCode;
        var isTypeSignature = false;
        if (signature.Length == 0)
        {
            if (!_idToSignatureDetails.TryGetValue(intId, out var previousMappedId))
                throw new Exception($"Id ({intId}) overriden in configuration line '{line}' is not defined by any previous lines.");

            (referenceHashCode, isTypeSignature)  = previousMappedId;
        }
        else
        {
            isTypeSignature = line.AsSpan().IndexOf("::") == -1; // member signatures must have a :: as a declaring type name/member name separator

            //TODO: When we switch from netstandard to *any* .NET BCL, remove the ToString() and call String.GetHashCode(signature) : https://learn.microsoft.com/en-us/dotnet/api/system.string.gethashcode?view=net-9.0#system-string-gethashcode(system-readonlyspan((system-char)))
            referenceHashCode = signature.ToString().GetHashCode();
            _idToSignatureDetails[intId] = new (referenceHashCode, isTypeSignature);

View on GitHub (pinned to 225b0fbdb5)

Solutions

  1. Change the id to an integer, e.g. ':1001 | signature | error'.
  2. Ensure ids are unique and numeric across the file.

Example fix

// before
:FILE_OPEN | System.IO.File::Open | error
// after
:1001 | System.IO.File::Open | error
Defensive patterns

Strategy: validation

Validate before calling

// Rule ids must be integers.
var id = token.Slice(1); // after ':'
if (!Int32.TryParse(id, out _))
    throw new FormatException($"Rule id is not a number: '{line}'");

Try / catch

try { config = RestrictedApisConfig.Load(path); }
catch (Exception ex) when (ex.Message.Contains("Id must be a number"))
{ /* replace the non-numeric id with an integer */ }

Prevention

When it happens

Trigger: A rule line whose ':id' token is non-numeric, e.g. ':abc | signature | error'.

Common situations: Using a string/label as an id, typos, or copy-paste from a non-numeric identifier scheme.

Related errors

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/8b37dce42b5f1ddd. Report an issue: GitHub.