[fix] allow invalidating variables from @const declared function (#7858)

src/compiler/compile/nodes/shared/Expression.ts

@@ -274,8 +274,38 @@ export default class Expression {
 					);
 
 					const declaration = b`const ${id} = ${node}`;
+					const extract_functions = () => {
+						const deps = Array.from(contextual_dependencies);
+						const function_expression = node as FunctionExpression;
+
+						const has_args = function_expression.params.length > 0;
+						function_expression.params = [
+							...deps.map(name => ({ type: 'Identifier', name } as Identifier)),
+							...function_expression.params
+						];
+
+						const context_args = deps.map(name => block.renderer.reference(name, ctx));
+
+						component.partly_hoisted.push(declaration);
+
+						block.renderer.add_to_context(id.name);
+						const callee = block.renderer.reference(id);
+
+						this.replace(id as any);
+
+						const func_declaration = has_args
+							? b`function ${id}(...args) {
+								return ${callee}(${context_args}, ...args);
+							}`
+							: b`function ${id}() {
+								return ${callee}(${context_args});
+							}`;
+						return { deps, func_declaration };
+					};
 
 					if (owner.type === 'ConstTag') {
+						// we need a combo block/init recipe
+						if (contextual_dependencies.size === 0) {
 							let child_scope = scope;
 							walk(node, {
 								enter(node: Node, parent: any) {
@@ -289,6 +319,10 @@ export default class Expression {
 									if (map.has(node)) child_scope = child_scope.parent;
 								}
 							});
+						} else {
+							const { func_declaration } = extract_functions();
+							this.replace(func_declaration[0]);
+						}
 					} else if (dependencies.size === 0 && contextual_dependencies.size === 0) {
 						// we can hoist this out of the component completely
 						component.fully_hoisted.push(declaration);
@@ -309,31 +343,7 @@ export default class Expression {
 						this.replace(block.renderer.reference(id));
 					} else {
 						// we need a combo block/init recipe
-						const deps = Array.from(contextual_dependencies);
-						const function_expression = node as FunctionExpression;
-
-						const has_args = function_expression.params.length > 0;
-						function_expression.params = [
-							...deps.map(name => ({ type: 'Identifier', name } as Identifier)),
-							...function_expression.params
-						];
-
-						const context_args = deps.map(name => block.renderer.reference(name));
-
-						component.partly_hoisted.push(declaration);
-
-						block.renderer.add_to_context(id.name);
-						const callee = block.renderer.reference(id);
-
-						this.replace(id as any);
-
-						const func_declaration = has_args
-							? b`function ${id}(...args) {
-								return ${callee}(${context_args}, ...args);
-							}`
-							: b`function ${id}() {
-								return ${callee}(${context_args});
-							}`;
+						const { deps, func_declaration } = extract_functions();
 
 						if (owner.type === 'Attribute' && owner.parent.name === 'slot') {
 							const dep_scopes = new Set<INode>(deps.map(name => template_scope.get_owner(name)));

test/runtime/samples/const-tag-invalidate/_config.js

@@ -0,0 +1,34 @@
+export default {
+	html: `
+		<div>[Y] A <button>Toggle</button></div>
+		<div>[N] B <button>Toggle</button></div>
+		<div>[N] C <button>Toggle</button></div>
+	`,
+	async test({ component, target, assert, window }) {
+		const [btn1, btn2, btn3] = target.querySelectorAll('button');
+		await btn1.dispatchEvent(new window.MouseEvent('click'));
+		await btn2.dispatchEvent(new window.MouseEvent('click'));
+
+		assert.htmlEqual(target.innerHTML, `
+			<div>[N] A <button>Toggle</button></div>
+			<div>[Y] B <button>Toggle</button></div>
+			<div>[N] C <button>Toggle</button></div>
+		`);
+
+		await btn2.dispatchEvent(new window.MouseEvent('click'));
+
+		assert.htmlEqual(target.innerHTML, `
+			<div>[N] A <button>Toggle</button></div>
+			<div>[N] B <button>Toggle</button></div>
+			<div>[N] C <button>Toggle</button></div>
+		`);
+
+		await btn3.dispatchEvent(new window.MouseEvent('click'));
+
+		assert.htmlEqual(target.innerHTML, `
+			<div>[N] A <button>Toggle</button></div>
+			<div>[N] B <button>Toggle</button></div>
+			<div>[Y] C <button>Toggle</button></div>
+		`);
+	}
+};

test/runtime/samples/const-tag-invalidate/main.svelte

@@ -0,0 +1,16 @@
+<script>
+	let items = [
+		{ name: 'A', selected: true },
+		{ name: 'B', selected: false },
+		{ name: 'C', selected: false },
+	]
+</script>
+
+{#each items as item}
+	{@const toggle = () => item.selected = !item.selected}
+	<div>
+		{item.selected ? '[Y]' : '[N]'}
+		{item.name}
+		<button on:click={toggle}>Toggle</button>
+	</div>
+{/each}