optimise spread code by passing false to get_spread_update for static attributes

src/compiler/compile/render_dom/wrappers/Element/index.ts

@@ -676,7 +676,7 @@ export default class ElementWrapper extends Wrapper {
 
 					initial_props.push(snippet);
 
-					updates.push(condition ? x`${condition} && ${snippet}` : snippet);
+					updates.push(condition ? x`${condition} && ${snippet}` : x`false`);
 				} else {
 					const metadata = attr.get_metadata();
 					const name = attr.is_indirectly_bound_value()
@@ -685,17 +685,14 @@ export default class ElementWrapper extends Wrapper {
 					const snippet = x`{ ${name}: ${attr.get_value(block)} }`;
 					initial_props.push(snippet);
 
-					updates.push(condition ? x`${condition} && ${snippet}` : snippet);
+					updates.push(condition ? x`${condition} && ${snippet}` : x`false`);
 				}
 			});
 
 		block.chunks.init.push(b`
 			let ${levels} = [${initial_props}];
 
-			let ${data} = {};
+			let ${data} = @get_attributes_for_spread(${levels});
-			for (let #i = 0; #i < ${levels}.length; #i += 1) {
-				${data} = @assign(${data}, ${levels}[#i]);
-			}
 		`);
 
 		const fn = this.node.namespace === namespaces.svg ? x`@set_svg_attributes` : x`@set_attributes`;

src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts

@@ -252,7 +252,7 @@ export default class InlineComponentWrapper extends Wrapper {
 
 					changes.push(
 						unchanged
-							? x`${levels}[${i}]`
+							? x`false`
 							: condition
 							? x`${condition} && ${change_object}`
 							: change_object
@@ -266,9 +266,7 @@ export default class InlineComponentWrapper extends Wrapper {
 				`);
 
 				statements.push(b`
-					for (let #i = 0; #i < ${levels}.length; #i += 1) {
+					${props} = @assign(${props}, @get_attributes_for_spread(${levels}))
-						${props} = @assign(${props}, ${levels}[#i]);
-					}
 				`);
 
 				if (all_dependencies.size) {

src/runtime/internal/spread.ts

@@ -1,3 +1,5 @@
+import { assign } from "./utils";
+
 export function get_spread_update(levels, updates) {
 	const update = {};
 
@@ -11,7 +13,7 @@ export function get_spread_update(levels, updates) {
 
 		if (n) {
 			for (const key in o) {
-				if (!(key in n)) to_null_out[key] = 1;
+				if (!(key in n) && !accounted_for[key]) to_null_out[key] = 1;
 			}
 
 			for (const key in n) {
@@ -24,6 +26,11 @@ export function get_spread_update(levels, updates) {
 			levels[i] = n;
 		} else {
 			for (const key in o) {
+				// if spreads decides to null out the key
+				// should reset it back for static attribute
+				if (to_null_out[key]) {
+					update[key] = o[key];
+				}
 				accounted_for[key] = 1;
 			}
 		}
@@ -36,6 +43,14 @@ export function get_spread_update(levels, updates) {
 	return update;
 }
 
+export function get_attributes_for_spread(levels) {
+	let attrs = {};
+	for (let i = 0; i < levels.length; i += 1) {
+		attrs = assign(attrs, levels[i]);
+	}
+	return attrs;
+}
+
 export function get_spread_object(spread_props) {
 	return typeof spread_props === 'object' && spread_props !== null ? spread_props : {};
 }