stride3d/stride · error · AnchorNotFoundException

Unable to find alias

Error message

Unable to find alias

What it means

While reading YAML, an alias node like *anchorName was encountered, but the AnchorSerializer has no recorded object for that alias — the anchor (&name) was never defined earlier in the document or was not kept. This throws an AnchorNotFoundException carrying 'Unable to find alias'.

Solutions

1. Fix the YAML so every alias has a preceding matching anchor definition (&name) in the same document
2. Remove or inline the dangling alias if shared data is no longer needed
3. Catch YamlException/AnchorNotFoundException during deserialization and report the document location

Example fix

// before (yaml)
value: *missingAnchor
// after (yaml)
base: &missingAnchor { x: 1 }
value: *missingAnchor

try { return serializer.Deserialize(reader, type); } catch (YamlException ex) when (ex.InnerException is AnchorNotFoundException) { throw new InvalidDataException($"Dangling YAML alias at {ex.Start}-{ex.End}", ex); }

When it happens

Trigger: Deserializing a YAML document containing `*alias` whose matching `&alias` anchor is absent, out of order, or stripped by preprocessing/merging of documents.

Common situations: Hand-edited YAML where an anchor was renamed/deleted; tooling that re-emits YAML without preserving anchors; concatenating YAML fragments where the anchor lives in another file.

Related errors

• Anchor value must contain alphanumerical characters only.
• Anchor value must not be empty.
• Cannot add item with key
• Cannot deserialize collection to readonly collection type
• Cannot deserialize collection to type

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/313af8097fb7c19b. Report an issue: GitHub.

Appendix: source

Thrown at sources/core/Stride.Core.Yaml/Serialization/Serializers/AnchorSerializer.cs:81

        public bool TryGetAliasValue(string alias, out object value)
        {
            return aliasToObject.TryGetValue(alias, out value);
        }

        public override object ReadYaml(ref ObjectContext objectContext)
        {
            var context = objectContext.SerializerContext;
            var reader = context.Reader;
            object value = null;

            // Process Anchor alias (*oxxx)
            var alias = reader.Allow<AnchorAlias>();
            if (alias != null)
            {
                // Return an alias or directly the value
                if (!aliasToObject.TryGetValue(alias.Value, out value))
                {
                    throw new AnchorNotFoundException(alias.Value, alias.Start, alias.End, "Unable to find alias");
                }
                return value;
            }

            // Test if current node has an anchor &oxxx
            string anchor = null;
            var nodeEvent = reader.Peek<NodeEvent>();
            if (nodeEvent != null && !string.IsNullOrEmpty(nodeEvent.Anchor))
            {
                anchor = nodeEvent.Anchor;
            }

            // Deserialize the current node
            value = base.ReadYaml(ref objectContext);

            // Store Anchor (&oxxx) and override any defined anchor 
            if (anchor != null)
            {

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