chore: tweak each block code (#15094)

Author: Rich-Harris

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

@@ -35,10 +35,6 @@ export function EachBlock(node, context) {
 		context.state.template.push('<!>');
 	}
 
-	if (each_node_meta.array_name !== null) {
-		context.state.init.push(b.const(each_node_meta.array_name, b.thunk(collection)));
-	}
-
 	let flags = 0;
 
 	if (node.metadata.keyed && node.index) {
@@ -120,8 +116,21 @@ export function EachBlock(node, context) {
 		return [array, ...transitive_dependencies];
 	});
 
-	if (each_node_meta.array_name) {
-		indirect_dependencies.push(b.call(each_node_meta.array_name));
+	/** @type {Identifier | null} */
+	let collection_id = null;
+
+	// Check if inner scope shadows something from outer scope.
+	// This is necessary because we need access to the array expression of the each block
+	// in the inner scope if bindings are used, in order to invalidate the array.
+	for (const [name] of context.state.scope.declarations) {
+		if (context.state.scope.parent?.get(name) != null) {
+			collection_id = context.state.scope.root.unique('$$array');
+			break;
+		}
+	}
+
+	if (collection_id) {
+		indirect_dependencies.push(b.call(collection_id));
 	} else {
 		indirect_dependencies.push(collection);
 
@@ -195,7 +204,7 @@ export function EachBlock(node, context) {
 					// TODO 6.0 this only applies in legacy mode, reassignments are
 					// forbidden in runes mode
 					return b.member(
-						each_node_meta.array_name ? b.call(each_node_meta.array_name) : collection,
+						collection_id ? b.call(collection_id) : collection,
 						(flags & EACH_INDEX_REACTIVE) !== 0 ? get_value(index) : index,
 						true
 					);
@@ -207,7 +216,7 @@ export function EachBlock(node, context) {
 				uses_index = true;
 
 				const left = b.member(
-					each_node_meta.array_name ? b.call(each_node_meta.array_name) : collection,
+					collection_id ? b.call(collection_id) : collection,
 					(flags & EACH_INDEX_REACTIVE) !== 0 ? get_value(index) : index,
 					true
 				);
@@ -283,16 +292,17 @@ export function EachBlock(node, context) {
 		);
 	}
 
+	const render_args = [b.id('$$anchor'), item];
+	if (uses_index || collection_id) render_args.push(index);
+	if (collection_id) render_args.push(collection_id);
+
 	/** @type {Expression[]} */
 	const args = [
 		context.state.node,
 		b.literal(flags),
-		each_node_meta.array_name ? each_node_meta.array_name : b.thunk(collection),
+		b.thunk(collection),
 		key_function,
-		b.arrow(
-			uses_index ? [b.id('$$anchor'), item, index] : [b.id('$$anchor'), item],
-			b.block(declarations.concat(block.body))
-		)
+		b.arrow(render_args, b.block(declarations.concat(block.body)))
 	];
 
 	if (node.fallback) {

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

@@ -575,21 +575,10 @@ export function create_scopes(ast, root, allow_reactive_declarations, parent) {
 			}
 			if (node.fallback) visit(node.fallback, { scope });
 
-			// Check if inner scope shadows something from outer scope.
-			// This is necessary because we need access to the array expression of the each block
-			// in the inner scope if bindings are used, in order to invalidate the array.
-			let needs_array_deduplication = false;
-			for (const [name] of scope.declarations) {
-				if (state.scope.get(name) !== null) {
-					needs_array_deduplication = true;
-				}
-			}
-
 			node.metadata = {
 				expression: create_expression_metadata(),
 				keyed: false,
 				contains_group_binding: false,
-				array_name: needs_array_deduplication ? state.scope.root.unique('$$array') : null,
 				index: scope.root.unique('$$index'),
 				declarations: scope.declarations,
 				is_controlled: false

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

@@ -414,8 +414,6 @@ export namespace AST {
 			expression: ExpressionMetadata;
 			keyed: boolean;
 			contains_group_binding: boolean;
-			/** Set if something in the array expression is shadowed within the each block */
-			array_name: Identifier | null;
 			index: Identifier;
 			declarations: Map<string, Binding>;
 			/**

packages/svelte/src/internal/client/dom/blocks/each.js

@@ -271,7 +271,7 @@ export function each(node, flags, get_collection, get_key, render_fn, fallback_f
  * @param {Array<V>} array
  * @param {EachState} state
  * @param {Element | Comment | Text} anchor
- * @param {(anchor: Node, item: MaybeSource<V>, index: number | Source<number>) => void} render_fn
+ * @param {(anchor: Node, item: MaybeSource<V>, index: number | Source<number>, collection: () => V[]) => void} render_fn
  * @param {number} flags
  * @param {boolean} is_inert
  * @param {(value: V, index: number) => any} get_key
@@ -510,7 +510,7 @@ function update_item(item, value, index, type) {
  * @param {V} value
  * @param {unknown} key
  * @param {number} index
- * @param {(anchor: Node, item: V | Source<V>, index: number | Value<number>) => void} render_fn
+ * @param {(anchor: Node, item: V | Source<V>, index: number | Value<number>, collection: () => V[]) => void} render_fn
  * @param {number} flags
  * @param {() => V[]} get_collection
  * @returns {EachItem}
@@ -559,7 +559,7 @@ function create_item(
 	current_each_item = item;
 
 	try {
-		item.e = branch(() => render_fn(anchor, v, i), hydrating);
+		item.e = branch(() => render_fn(anchor, v, i, get_collection), hydrating);
 
 		item.e.prev = prev && prev.e;
 		item.e.next = next && next.e;