Initial

module/data/fields/_module.mjs

@@ -1,3 +1,4 @@
 export { default as FormulaField } from './formulaField.mjs';
 export { default as ForeignDocumentUUIDField } from './foreignDocumentUUIDField.mjs';
 export { default as ForeignDocumentUUIDArrayField } from './foreignDocumentUUIDArrayField.mjs';
+export { default as ItemLinksField } from './itemLinksField.mjs';

module/data/fields/itemLinksField.mjs

@@ -0,0 +1,32 @@
+export default class ItemLinksField extends foundry.data.fields.TypedObjectField {
+    /**
+     * @param {DataFieldOptions} [options]    Options which configure the behavior of the field.
+     * @param {DataFieldContext} [context]    Additional context which describes the field
+     */
+    constructor(options, context) {
+        super(
+            new foundry.data.fields.StringField({
+                choices: CONFIG.DH.ITEM.featureSubTypes,
+                nullable: true,
+                initial: null
+            }),
+            options,
+            context
+        );
+    }
+
+    /** @inheritDoc */
+    static get _defaults() {
+        return mergeObject(super._defaults, { validateKey: this.validateKey });
+    }
+
+    /**
+     * @param {Object} [value]    The candidate object to be added.
+     */
+    static validateKey(value) {
+        return true;
+        const parsed = foundry.utils.parseUuid(value);
+        if (!parsed || parsed.type !== CONFIG.Item.documentClass.documentName) return false;
+        if (!foundry.packages.BasePackage.validateId(parsed.documentId)) return false;
+    }
+}

module/data/item/ancestry.mjs

@@ -20,18 +20,10 @@ export default class DHAncestry extends BaseDataItem {
     }
 
     get primaryFeature() {
-        return (
-            this.features.find(x => x?.system?.subType === CONFIG.DH.ITEM.featureSubTypes.primary) ??
-            (this.features.filter(x => !x).length > 0 ? {} : null)
-        );
+        return this.features.find(x => x.system.itemLinks[this.parent.id] === CONFIG.DH.ITEM.featureSubTypes.primary);
     }
 
     get secondaryFeature() {
-        return (
-            this.features.find(x => x?.system?.subType === CONFIG.DH.ITEM.featureSubTypes.secondary) ??
-            (this.features.filter(x => !x || x.system.subType === CONFIG.DH.ITEM.featureSubTypes.primary).length > 1
-                ? {}
-                : null)
-        );
+        return this.features.find(x => x.system.itemLinks[this.parent.id] === CONFIG.DH.ITEM.featureSubTypes.secondary);
     }
 }

module/data/item/base.mjs

@@ -8,6 +8,8 @@
  * @property {boolean} isInventoryItem- Indicates whether items of this type is a Inventory Item
  */
 
+import ItemLinksField from '../fields/itemLinksField.mjs';
+
 const fields = foundry.data.fields;
 
 export default class BaseDataItem extends foundry.abstract.TypeDataModel {
@@ -21,7 +23,8 @@ export default class BaseDataItem extends foundry.abstract.TypeDataModel {
             hasDescription: false,
             hasResource: false,
             isQuantifiable: false,
-            isInventoryItem: false
+            isInventoryItem: false,
+            isItemLinkable: true
         };
     }
 
@@ -69,6 +72,10 @@ export default class BaseDataItem extends foundry.abstract.TypeDataModel {
         if (this.metadata.isQuantifiable)
             schema.quantity = new fields.NumberField({ integer: true, initial: 1, min: 0, required: true });
 
+        if (this.metadata.isItemLinkable) {
+            schema.itemLinks = new ItemLinksField();
+        }
+
         return schema;
     }
 

module/data/item/feature.mjs

@@ -8,7 +8,8 @@ export default class DHFeature extends BaseDataItem {
             label: 'TYPES.Item.feature',
             type: 'feature',
             hasDescription: true,
-            hasResource: true
+            hasResource: true,
+            isItemLinkable: true
         });
     }