{"record":{"id":"53fd327217343c51","repo":"stride3d/stride","slug":"unable-to-find-a-type-for-this-element-node","errorCode":null,"errorMessage":"Unable to find a type for this element [{node}]","messagePattern":"Unable to find a type for this element \\[(.+?)\\]","errorType":"exception","errorClass":"YamlException","httpStatus":null,"severity":"error","filePath":"sources/core/Stride.Core.Yaml/Serialization/Serializers/TagTypeSerializer.cs","lineNumber":131,"sourceCode":"            // This allow to load any YAML documents into dictionary/list\n            // automatically\n            if ((type == null || type == typeof(object)) && value == null)\n            {\n                // If the node is a sequence start, fallback to a IList<object>\n                if (node is SequenceStart)\n                {\n                    type = typeof(IList<object>);\n                }\n                else if (node is MappingStart)\n                {\n                    // If the node is a mapping start, fallback to a IDictionary<object, object>\n                    type = typeof(IDictionary<object, object>);\n                }\n            }\n\n            if (type == null && value == null)\n            {\n                throw new YamlException(node.Start, node.End, $\"Unable to find a type for this element [{node}]\");\n            }\n\n            if (type == null)\n            {\n                type = value.GetType();\n            }\n            else if (typeFromTag != null && value != null && value.GetType() != typeFromTag)\n            {\n                // Reset the instance if the value loaded from the tag is not of the same type then the value already instantiated\n                type = typeFromTag;\n                objectContext.Instance = null;\n            }\n\n            objectContext.Descriptor = objectContext.SerializerContext.FindTypeDescriptor(type);\n\n            // If this is a nullable descriptor, use its underlying type directly\n            if (objectContext.Descriptor is NullableDescriptor)\n            {","sourceCodeStart":113,"sourceCodeEnd":149,"githubUrl":"https://github.com/stride3d/stride/blob/96fad776d210c221682aac1ccdf4c79dc046fc38/sources/core/Stride.Core.Yaml/Serialization/Serializers/TagTypeSerializer.cs#L113-L149","documentation":"TagTypeSerializer.ReadYaml throws this when it cannot determine a .NET type for the node being read (type == null) and the node also has no value to infer the type from (value == null). Without a tag, descriptor type, or value, deserialization cannot proceed.","triggerScenarios":"Deserializing a node whose type cannot be derived: no tag, no compatible expected-type descriptor, and the produced value is null — typically an aliased/untagged null node in a context where the expected type is unknown.","commonSituations":"YAML documents with untyped null entries in polymorphic collections; alias anchors resolving to nothing; schema configuration where the property descriptor's type was not resolved; hand-written YAML omitting tags where the library requires them.","solutions":["Add an explicit type tag to the YAML node so the serializer knows the type.","Ensure the target property/field has a concrete declared type (not object) in the model.","Fix alias anchors so they point to existing nodes with values.","Check serialization output of the same model — if it emits untyped nulls it cannot read back, adjust the model or serializer settings."],"exampleFix":"// before (YAML)\nitems:\n  -\n// after\nitems:\n  - !MyApp.Item\n    id: 1","handlingStrategy":"validation","validationCode":"static bool NodeIsUntypedNull(YamlNode node) => node is YamlScalarNode s && (s.Value == null || s.Value == \"~\") && string.IsNullOrEmpty(s.Tag);","typeGuard":null,"tryCatchPattern":"try { return serializer.Deserialize(reader); } catch (YamlException ex) when (ex.Message.StartsWith(\"Unable to find a type\")) { throw new InvalidOperationException(\"YAML contains an untyped null element; add a type tag or give the target member a concrete type\", ex); }","preventionTips":["Use concrete property types instead of object in serializable models.","Emit explicit type tags for polymorphic collection items.","Fix dangling YAML anchors/aliases before deserializing.","Round-trip test models to catch untyped-null emission early."],"tags":["yaml","deserialization","type-resolution","null"],"backgroundTag":"type-mismatch","analyzedSha":"96fad776d210c221682aac1ccdf4c79dc046fc38","analyzedAt":"2026-09-14T02:59:31.279Z","contentChangedAt":"2026-09-14T02:59:31.279Z","schemaVersion":2},"datasetVersion":"2026-09-23T08:17:48.524Z"}