stride3d/stride · error · SyntaxErrorException

While scanning a %YAML directive, did not find expected…

Error message

While scanning a %YAML directive, did not find expected digit or '.' character.

What it means

Thrown by the YAML Scanner while parsing the version number of a %YAML directive. After the major version digits the scanner requires a '.' before the minor version; if the next character is not a '.' (or a digit was missing) the directive is malformed.

Solutions

Fix the directive to full 'major.minor' form: '%YAML 1.1' or '%YAML 1.2'.
Remove the %YAML directive entirely if version declaration is unnecessary (the parser defaults to 1.1).
Regenerate the file from its source/template if it was truncated.
Validate with a YAML parser before loading to catch directive typos early.

Example fix

// before
%YAML 1
---
// after
%YAML 1.1
---

Defensive patterns

Strategy: validation

Validate before calling

bool IsValidYamlVersionDirective(string line) =>
    !line.StartsWith("%YAML") ||
    System.Text.RegularExpressions.Regex.IsMatch(line, "^%YAML \\d+\\.\\d+\\s*$");

Try / catch

try
{
    var obj = Deserializer.FromFile(path);
}
catch (SyntaxErrorException ex)
{
    Log.Error(ex, "Bad %YAML version at line {Line}", ex.Start.Line);
    throw new YamlConfigException("%YAML directive must be 'major.minor'", ex);
}

Prevention

Always write the full version: '%YAML 1.1' or '%YAML 1.2'
Omit the %YAML directive when the default version is acceptable
Lint YAML files in CI to catch directive typos

When it happens

Trigger: Parsing YAML whose %YAML directive has a malformed version, e.g. '%YAML 1' (no dot/minor), '%YAML x.y' (non-digit major), or '%YAML 1.1.1' style corruption where the expected '.' is absent.

Common situations: Hand-edited version directives; tools writing '%YAML 1' instead of '%YAML 1.1'; truncated files cut off mid-directive.

Related errors

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/f353f30d430276fd. Report an issue: GitHub.

Appendix: source

Thrown at sources/core/Stride.Core.Yaml/Scanner.cs:2054

        /// Scan the value of VERSION-DIRECTIVE.
        ///
        /// Scope:
        ///      %YAML   1.1     # a comment \n
        ///           ^^^^^^
        /// </summary>
        private Token ScanVersionDirectiveValue(Mark start)
        {
            SkipWhitespaces();

            // Consume the major version number.

            int major = ScanVersionDirectiveNumber(start);

            // Eat '.'.

            if (!analyzer.Check('.'))
            {
                throw new SyntaxErrorException(start, mark, "While scanning a %YAML directive, did not find expected digit or '.' character.");
            }

            Skip();

            // Consume the minor version number.

            int minor = ScanVersionDirectiveNumber(start);

            return new VersionDirective(new Version(major, minor), start, start);
        }

        /// <summary>
        /// Scan the value of a TAG-DIRECTIVE token.
        ///
        /// Scope:
        ///      %TAG    !yaml!  tag:yaml.org,2002:  \n
        ///          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        /// </summary>

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