stride3d/stride · error · SyntaxErrorException

While scanning a %YAML directive, find extremely long…

Error message

While scanning a %YAML directive, find extremely long version number.

What it means

Scanner.ScanVersionDirectiveValue reads the %YAML directive's version numbers digit by digit and caps each component at MaxVersionNumberLength digits. A version component longer than that (dozens of digits) is nonsensical, so the scanner throws SyntaxErrorException to bound runaway input.

Solutions

  1. Use a valid YAML version, e.g. '%YAML 1.1' or '%YAML 1.2'.
  2. Remove the %YAML directive if your document does not need to declare a version.
  3. Check the file for duplication/corruption around the directive line.
  4. Catch SyntaxErrorException and report the mark to locate the bad directive.

Example fix

// before (input.yaml)
%YAML 123456789012345678901234567890.1

// after (input.yaml)
%YAML 1.1
Defensive patterns

Strategy: validation

Validate before calling

// C#
var m = System.Text.RegularExpressions.Regex.Match(yamlText ?? "", @"^%YAML\s+(\d+)\.(\d+)", System.Text.RegularExpressions.RegexOptions.Multiline);
if (yamlText != null && yamlText.Contains("%YAML") && (!m.Success || m.Groups[1].Value.Length > 9 || m.Groups[2].Value.Length > 9))
    throw new FormatException("%YAML directive must have a short numeric major.minor version, e.g. 1.1.");

Try / catch

try { deserializer.Deserialize(reader, targetType); }
catch (SyntaxErrorException ex) { throw new YamlConfigException($"Bad %YAML version at line {ex.Start.Line}", ex); }

Prevention

When it happens

Trigger: A %YAML directive with an absurdly long version number, e.g. '%YAML 111111111111111111111.1' or a garbage line like '%YAML 00000000000000000000' whose digit run exceeds the limit.

Common situations: Corrupted or generated garbage in a directive line; concatenation bugs that duplicated digits; obfuscation/fuzzing input; accidental paste into a directives section.

Related errors

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/5af2d3d7f74770de. Report an issue: GitHub.

Appendix: source

Thrown at sources/core/Stride.Core.Yaml/Scanner.cs:2281

        ///      %YAML   1.1     # a comment \n
        ///              ^
        ///      %YAML   1.1     # a comment \n
        ///                ^
        /// </summary>
        private int ScanVersionDirectiveNumber(Mark start)
        {
            int value = 0;
            int length = 0;

            // Repeat while the next character is digit.

            while (analyzer.IsDigit())
            {
                // Check if the number is too long.

                if (++length > MaxVersionNumberLength)
                {
                    throw new SyntaxErrorException(start, mark, "While scanning a %YAML directive, find extremely long version number.");
                }

                value = value*10 + analyzer.AsDigit();

                Skip();
            }

            // Check if the number was present.

            if (length == 0)
            {
                throw new SyntaxErrorException(start, mark, "While scanning a %YAML directive, did not find expected version number.");
            }

            return value;
        }

        /// <summary>

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