fix #538

Author: mProjectsCode

packages/core/src/metadata/IMetadataSubscription.ts

@@ -26,6 +26,8 @@ export interface IMetadataSubscription {
 	delete: () => void;
 	/**
 	 * Called by the metadata manager when the cache receives an update that concerns this subscription.
+	 * This is NOT called with a clone of the value, so the subscription should not modify the value.
+	 * If the subscription can't guarantee that the value won't be modified, it should clone the value.
 	 *
 	 * @param value
 	 * @returns Whether the subscription has updated, i.e. the value was different from the current memorized value.

packages/core/src/metadata/MetadataManager.ts

@@ -250,7 +250,8 @@ export class MetadataManager {
 		const cacheItem = source.subscribe(subscription);
 		cacheItem.cyclesWithoutListeners = 0;
 
-		subscription.onUpdate(source.readCacheItem(cacheItem, subscription.bindTarget.storageProp));
+		const initialValue = source.readCacheItem(cacheItem, subscription.bindTarget.storageProp);
+		subscription.onUpdate(initialValue);
 	}
 
 	/**

packages/core/src/metadata/MetadataSubscription.ts

@@ -50,22 +50,19 @@ export class MetadataSubscription implements IMetadataSubscription {
 		const currentValue = this.metadataManager.readShortLived(this.bindTarget);
 		if (!areObjectsEqual(currentValue, value)) {
 			this.value = value;
+			// note: write already clones the value
 			this.metadataManager.write(value, this.bindTarget, this.uuid);
 		}
 	}
 
-	/**
-	 * DO NOT CALL!
-	 *
-	 * Notifies the subscription of an updated value in the cache.
-	 *
-	 * @param value
-	 */
 	public onUpdate(value: unknown): boolean {
+		// The value is NOT cloned, but that's fine for the comparison.
+		// If we actually notify the callback, we need to clone the value, as we can't guarantee that the callback won't modify it.
 		try {
 			if (!areObjectsEqual(this.value, value)) {
-				this.value = value;
-				this.callbackSignal.set(value);
+				const clonedValue = structuredClone(value);
+				this.value = clonedValue;
+				this.callbackSignal.set(clonedValue);
 
 				return true;
 			}

packages/core/src/parsers/bindTargetParser/BindTargetParser.ts

@@ -55,24 +55,17 @@ export class BindTargetParser {
 		filePath: string,
 		scope?: BindTargetScope,
 	): BindTargetDeclaration {
-		const bindTargetDeclaration: BindTargetDeclaration = {} as BindTargetDeclaration;
-
-		// listen to children
-		bindTargetDeclaration.listenToChildren = unvalidatedBindTargetDeclaration.listenToChildren;
-
 		// storage prop
-		bindTargetDeclaration.storageProp = new PropPath(
+		const storageProp = new PropPath(
 			unvalidatedBindTargetDeclaration.storageProp.map(x => new PropAccess(x.type, x.prop.value)),
 		);
 
 		// storage type
+		let storageType: string;
 		if (unvalidatedBindTargetDeclaration.storageType === undefined) {
-			bindTargetDeclaration.storageType = this.mb.metadataManager.defaultSource;
+			storageType = this.mb.metadataManager.defaultSource;
 		} else {
-			bindTargetDeclaration.storageType = this.validateStorageType(
-				unvalidatedBindTargetDeclaration.storageType,
-				fullDeclaration,
-			);
+			storageType = this.validateStorageType(unvalidatedBindTargetDeclaration.storageType, fullDeclaration);
 		}
 
 		// storage path
@@ -81,25 +74,28 @@ export class BindTargetParser {
 			value: filePath,
 		};
 
-		const source = this.mb.metadataManager.getSource(bindTargetDeclaration.storageType);
+		const source = this.mb.metadataManager.getSource(storageType);
 		if (source === undefined) {
 			throw new MetaBindInternalError({
 				errorLevel: ErrorLevel.CRITICAL,
 				effect: 'can not validate bind target',
-				cause: `Source '${bindTargetDeclaration.storageType}' not found. But validation was successful. This should not happen.`,
+				cause: `Source '${storageType}' not found. But validation was successful. This should not happen.`,
 				context: {
 					fullDeclaration: fullDeclaration,
 					sources: [...this.mb.metadataManager.sources.keys()],
 				},
 			});
 		}
 
-		bindTargetDeclaration.storagePath = source.validateStoragePath(
-			storagePathToValidate,
-			hadStoragePath,
-			fullDeclaration,
-			this,
-		);
+		const storagePath = source.validateStoragePath(storagePathToValidate, hadStoragePath, fullDeclaration, this);
+
+		// construct bind target declaration
+		const bindTargetDeclaration: BindTargetDeclaration = {
+			storageType: storageType,
+			storagePath: storagePath,
+			storageProp: storageProp,
+			listenToChildren: unvalidatedBindTargetDeclaration.listenToChildren,
+		};
 
 		// eslint-disable-next-line @typescript-eslint/no-unsafe-enum-comparison
 		if (source.id === BindTargetStorageType.SCOPE) {