feat: remove `$.unwrap` calls from `bind:group` (#12642)

* add each.metadata.keyed

* simplify

* feat: remove `$.unwrap` from `bind:group` code

* changeset

* regenerate types

.changeset/three-donkeys-jump.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+feat: remove `$.unwrap` calls from `bind:group`

packages/svelte/src/compiler/phases/2-analyze/index.js

@@ -1547,6 +1547,13 @@ const common_visitors = {
 	},
 	RenderTag(node, context) {
 		context.next({ ...context.state, render_tag: node });
+	},
+	EachBlock(node) {
+		if (node.key) {
+			// treat `{#each items as item, i (i)}` as a normal indexed block, everything else as keyed
+			node.metadata.keyed =
+				node.key.type !== 'Identifier' || !node.index || node.key.name !== node.index;
+		}
 	}
 };
 

packages/svelte/src/compiler/phases/3-transform/client/visitors/template.js

@@ -2409,10 +2409,7 @@ export const template_visitors = {
 
 		let flags = 0;
 
-		if (
-			node.key &&
-			(node.key.type !== 'Identifier' || !node.index || node.key.name !== node.index)
-		) {
+		if (node.metadata.keyed) {
 			flags |= EACH_KEYED;
 
 			if (node.index) {
@@ -2421,7 +2418,7 @@ export const template_visitors = {
 
 			// In runes mode, if key === item, we don't need to wrap the item in a source
 			const key_is_item =
-				node.key.type === 'Identifier' &&
+				/** @type {Expression} */ (node.key).type === 'Identifier' &&
 				node.context.type === 'Identifier' &&
 				node.context.name === node.key.name;
 
@@ -2614,8 +2611,11 @@ export const template_visitors = {
 		/** @type {Expression} */
 		let key_function = b.id('$.index');
 
-		if (node.key) {
-			const expression = /** @type {Expression} */ (context.visit(node.key, key_state));
+		if (node.metadata.keyed) {
+			const expression = /** @type {Expression} */ (
+				context.visit(/** @type {Expression} */ (node.key), key_state)
+			);
+
 			key_function = b.arrow([node.context, index], expression);
 		}
 
@@ -3049,11 +3049,12 @@ export const template_visitors = {
 					call_expr = b.call(`$.bind_focused`, state.node, setter);
 					break;
 				case 'group': {
-					/** @type {CallExpression[]} */
-					const indexes = [];
-					for (const parent_each_block of node.metadata.parent_each_blocks) {
-						indexes.push(b.call('$.unwrap', parent_each_block.metadata.index));
-					}
+					const indexes = node.metadata.parent_each_blocks.map((each) => {
+						// if we have a keyed block with an index, the index is wrapped in a source
+						return each.metadata.keyed && each.index
+							? b.call('$.get', each.metadata.index)
+							: each.metadata.index;
+					});
 
 					// We need to additionally invoke the value attribute signal to register it as a dependency,
 					// so that when the value is updated, the group binding is updated

packages/svelte/src/compiler/phases/scope.js

@@ -592,6 +592,7 @@ export function create_scopes(ast, root, allow_reactive_declarations, parent) {
 			}
 
 			node.metadata = {
+				keyed: false,
 				contains_group_binding: false,
 				array_name: needs_array_deduplication ? state.scope.root.unique('$$array') : null,
 				index: scope.root.unique('$$index'),

packages/svelte/src/compiler/types/template.d.ts

@@ -393,6 +393,7 @@ export interface EachBlock extends BaseNode {
 	index?: string;
 	key?: Expression;
 	metadata: {
+		keyed: boolean;
 		contains_group_binding: boolean;
 		/** Set if something in the array expression is shadowed within the each block */
 		array_name: Identifier | null;

packages/svelte/src/internal/client/dom/elements/bindings/input.js

@@ -73,13 +73,8 @@ export function bind_group(inputs, group_index, input, get_value, update) {
 
 	if (group_index !== null) {
 		for (var index of group_index) {
-			var group = binding_group;
-			// @ts-ignore
-			binding_group = group[index];
-			if (binding_group === undefined) {
-				// @ts-ignore
-				binding_group = group[index] = [];
-			}
+			// @ts-expect-error
+			binding_group = binding_group[index] ??= [];
 		}
 	}
 

packages/svelte/types/index.d.ts

@@ -1845,6 +1845,7 @@ declare module 'svelte/compiler' {
 		index?: string;
 		key?: Expression;
 		metadata: {
+			keyed: boolean;
 			contains_group_binding: boolean;
 			/** Set if something in the array expression is shadowed within the each block */
 			array_name: Identifier | null;