What causes "Anchor value must not be empty." in stride3d/stride?

Pass the actual anchor name to the AnchorAlias constructor

stride3d/stride · error · YamlException

Anchor value must not be empty.

Error message

Anchor value must not be empty.

What it means

AnchorAlias events represent *x references to an anchor; the alias value must be a non-empty string matching the anchor grammar. The constructor throws this YamlException (with position marks) when the alias value is null or empty, before any parsing/emitting proceeds.

Solutions

Pass the actual anchor name to the AnchorAlias constructor
Validate that the anchor string is non-empty before constructing the event
Skip emitting the alias (emit the anchored node inline instead) when no anchor name exists
Fix the upstream code that produced the empty anchor reference

Example fix

// before
var alias = new AnchorAlias(aliasName, start, end);
// after
if (string.IsNullOrEmpty(aliasName)) throw new InvalidOperationException("Alias name missing");
var alias = new AnchorAlias(aliasName, start, end);

Defensive patterns

Strategy: validation

Validate before calling

bool ok = !string.IsNullOrEmpty(aliasName);
if (!ok) throw new ArgumentException("Alias name is required");

Try / catch

try { var alias = new AnchorAlias(name, start, end); }
catch (YamlException ex) when (ex.Message.Contains("must not be empty")) { /* emit the node inline instead of an alias */ }

Prevention

Never interpolate anchor names from data that may be empty
Skip aliases when the anchor name was lost and inline the node instead
Validate anchor references when converting from other formats

When it happens

Trigger: new AnchorAlias("", start, end) or new AnchorAlias(null, start, end); alias nodes generated from deserialized data where the anchor name was lost or empty.

Common situations: Programmatic construction of YAML event graphs; pipelines that convert anchors/aliases from other formats and lose the name; templates that interpolate an anchor variable which resolved to an empty string.

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

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/b4cb0f3433a696a6. Report an issue: GitHub.

Appendix: source

Thrown at sources/core/Stride.Core.Yaml/Events/AnchorAlias.cs:85

        private readonly string value;

        /// <summary>
        /// Gets the value of the alias.
        /// </summary>
        public string Value { get { return value; } }

        /// <summary>
        /// Initializes a new instance of the <see cref="AnchorAlias"/> class.
        /// </summary>
        /// <param name="value">The value of the alias.</param>
        /// <param name="start">The start position of the event.</param>
        /// <param name="end">The end position of the event.</param>
        public AnchorAlias(string value, Mark start, Mark end)
            : base(start, end)
        {
            if (string.IsNullOrEmpty(value))
            {
                throw new YamlException(start, end, "Anchor value must not be empty.");
            }

            if (!NodeEvent.anchorValidator.IsMatch(value))
            {
                throw new YamlException(start, end, "Anchor value must contain alphanumerical characters only.");
            }

            this.value = value;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="AnchorAlias"/> class.
        /// </summary>
        /// <param name="value">The value of the alias.</param>
        public AnchorAlias(string value)
            : this(value, Mark.Empty, Mark.Empty)
        {
        }

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