banner: fix control config merge behaviour

src/lib/Banner.svelte

@@ -39,7 +39,7 @@
 			| null;
 		dismiss?: Omit<BannerControlButton, 'framed'> | null;
 		/** if true, accept and decline buttons are swapped with more info */
-		swap?: boolean;
+		swap?: boolean | null;
 	};
 
 	const defaultBannerControls: BannerControls = {
@@ -61,17 +61,34 @@
 
 	const mergeBannerControls = (
 		defaults: BannerControls,
-		overrides: BannerControls | null | undefined
+		overrides?: BannerControls | null
 	): BannerControls => {
-		if (!overrides) return defaults;
+		if (overrides == null) return { ...defaults };
 
-		return {
-			accept: overrides.accept ?? defaults.accept,
-			decline: overrides.decline ?? defaults.decline,
-			moreInfo: overrides.moreInfo ?? defaults.moreInfo,
-			dismiss: overrides.dismiss ?? defaults.dismiss,
-			swap: overrides.swap ?? defaults.swap
-		};
+		const result: BannerControls = { ...defaults };
+
+		const keys: (keyof BannerControls)[] = ['accept', 'decline', 'moreInfo', 'dismiss', 'swap'];
+
+		for (const key of keys) {
+			const ov = overrides[key];
+			if (ov === null) {
+				// explicit disable
+				result[key] = null;
+				continue;
+			}
+			if (ov === undefined) continue; // keep default
+			if (key === 'swap') {
+				result.swap = ov as boolean;
+				continue;
+			}
+			// shallow merge individual control fields
+			result[key] = {
+				...(defaults[key] ?? {}),
+				...(ov as any)
+			} as any;
+		}
+
+		return result;
 	};
 </script>
 

src/routes/+page.svelte

@@ -84,6 +84,7 @@
 	title="Manage Cookies"
 	controls={{
 		moreInfo: { label: 'More Info', type: 'link', href: '#!' },
+		dismiss: null,
 		swap: true
 	}}
 	onaccept={() => console.log('Cookies accepted!')}