module/data/fields/EphemeralObjectField.mjs

@@ -0,0 +1,29 @@
+/**
+ * This data field functions the same way as Foundry's ObjectField
+ * however it permits changes to internal properties to be tracked in
+ * a diff, without committing those changes to the database unless it's
+ * removing the entire object.
+ */
+export class EphemeralObjectField extends foundry.data.fields.ObjectField {
+
+	/**
+	 * Inverting the defaults from ObjectField since we don't want it to
+	 * be stored in the database anyway
+	 */
+	static get _defaults() {
+		return Object.assign(super._defaults, { required: false, nullable: true });
+	};
+
+	/**
+	 * When trying to diff the object, only allow deletions to go through,
+	 * otherwise ignore it entirely
+	 */
+	_updateDiff(key, value, options, state) {
+		if (
+			!value
+			|| (value instanceof foundry.data.operators.ForcedDeletion)
+		) {
+			return super._updateDiff(key, value, options, state);
+		};
+	};
+};