WIP

packages/svelte/src/compiler/phases/1-parse/state/tag.js

@@ -63,7 +63,10 @@ function open(parser) {
 			end: -1,
 			test: read_expression(parser),
 			consequent: create_fragment(),
-			alternate: null
+			alternate: null,
+			metadata: {
+				expression: create_expression_metadata()
+			}
 		});
 
 		parser.allow_whitespace();
@@ -244,7 +247,10 @@ function open(parser) {
 			error: null,
 			pending: null,
 			then: null,
-			catch: null
+			catch: null,
+			metadata: {
+				expression: create_expression_metadata()
+			}
 		});
 
 		if (parser.eat('then')) {
@@ -326,7 +332,10 @@ function open(parser) {
 			start,
 			end: -1,
 			expression,
-			fragment: create_fragment()
+			fragment: create_fragment(),
+			metadata: {
+				expression: create_expression_metadata()
+			}
 		});
 
 		parser.stack.push(block);
@@ -461,7 +470,10 @@ function next(parser) {
 				elseif: true,
 				test: expression,
 				consequent: create_fragment(),
-				alternate: null
+				alternate: null,
+				metadata: {
+					expression: create_expression_metadata()
+				}
 			});
 
 			parser.stack.push(child);
@@ -624,7 +636,10 @@ function special(parser) {
 			type: 'HtmlTag',
 			start,
 			end: parser.index,
-			expression
+			expression,
+			metadata: {
+				expression: create_expression_metadata()
+			}
 		});
 
 		return;
@@ -699,6 +714,9 @@ function special(parser) {
 				declarations: [{ type: 'VariableDeclarator', id, init, start: id.start, end: init.end }],
 				start: start + 2, // start at const, not at @const
 				end: parser.index - 1
+			},
+			metadata: {
+				expression: create_expression_metadata()
 			}
 		});
 	}
@@ -725,6 +743,7 @@ function special(parser) {
 			end: parser.index,
 			expression: /** @type {AST.RenderTag['expression']} */ (expression),
 			metadata: {
+				expression: create_expression_metadata(),
 				dynamic: false,
 				arguments: [],
 				path: [],

packages/svelte/src/compiler/phases/2-analyze/visitors/AwaitBlock.js

@@ -41,5 +41,8 @@ export function AwaitBlock(node, context) {
 
 	mark_subtree_dynamic(context.path);
 
-	context.next();
+	context.visit(node.expression, { ...context.state, expression: node.metadata.expression });
+	if (node.pending) context.visit(node.pending);
+	if (node.then) context.visit(node.then);
+	if (node.catch) context.visit(node.catch);
 }

packages/svelte/src/compiler/phases/2-analyze/visitors/ConstTag.js

@@ -32,5 +32,8 @@ export function ConstTag(node, context) {
 		e.const_tag_invalid_placement(node);
 	}
 
-	context.next();
+	const declaration = node.declaration.declarations[0];
+
+	context.visit(declaration.id);
+	context.visit(declaration.init, { ...context.state, expression: node.metadata.expression });
 }

packages/svelte/src/compiler/phases/2-analyze/visitors/HtmlTag.js

@@ -15,5 +15,5 @@ export function HtmlTag(node, context) {
 	// unfortunately this is necessary in order to fix invalid HTML
 	mark_subtree_dynamic(context.path);
 
-	context.next();
+	context.next({ ...context.state, expression: node.metadata.expression });
 }

packages/svelte/src/compiler/phases/2-analyze/visitors/IfBlock.js

@@ -17,5 +17,11 @@ export function IfBlock(node, context) {
 
 	mark_subtree_dynamic(context.path);
 
-	context.next();
+	context.visit(node.test, {
+		...context.state,
+		expression: node.metadata.expression
+	});
+
+	context.visit(node.consequent);
+	if (node.alternate) context.visit(node.alternate);
 }

packages/svelte/src/compiler/phases/2-analyze/visitors/KeyBlock.js

@@ -16,5 +16,6 @@ export function KeyBlock(node, context) {
 
 	mark_subtree_dynamic(context.path);
 
-	context.next();
+	context.visit(node.expression, { ...context.state, expression: node.metadata.expression });
+	context.visit(node.fragment);
 }

packages/svelte/src/compiler/phases/2-analyze/visitors/RenderTag.js

@@ -54,7 +54,7 @@ export function RenderTag(node, context) {
 
 	mark_subtree_dynamic(context.path);
 
-	context.visit(callee);
+	context.visit(callee, { ...context.state, expression: node.metadata.expression });
 
 	for (const arg of expression.arguments) {
 		const metadata = create_expression_metadata();

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

@@ -2,7 +2,7 @@
 /** @import { AST } from '#compiler' */
 /** @import { ComponentContext } from '../types' */
 import * as b from '../../../../utils/builders.js';
-import { build_legacy_expression } from './shared/utils.js';
+import { build_legacy_expression_2 } from './shared/utils.js';
 
 /**
  * @param {AST.AttachTag} node
@@ -11,7 +11,7 @@ import { build_legacy_expression } from './shared/utils.js';
 export function AttachTag(node, context) {
 	const expression = context.state.analysis.runes
 		? /** @type {Expression} */ (context.visit(node.expression))
-		: build_legacy_expression(node.expression, context);
+		: build_legacy_expression_2(context, node.expression, node.metadata.expression);
 	context.state.init.push(b.stmt(b.call('$.attach', context.state.node, b.thunk(expression))));
 	context.next();
 }

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

@@ -5,7 +5,7 @@ import { extract_identifiers } from '../../../../utils/ast.js';
 import * as b from '#compiler/builders';
 import { create_derived } from '../utils.js';
 import { get_value } from './shared/declarations.js';
-import { build_legacy_expression } from './shared/utils.js';
+import { build_legacy_expression_2 } from './shared/utils.js';
 
 /**
  * @param {AST.AwaitBlock} node
@@ -18,7 +18,7 @@ export function AwaitBlock(node, context) {
 	const expression = b.thunk(
 		context.state.analysis.runes
 			? /** @type {Expression} */ (context.visit(node.expression))
-			: build_legacy_expression(node.expression, context)
+			: build_legacy_expression_2(context, node.expression, node.metadata.expression)
 	);
 
 	let then_block;

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

@@ -14,7 +14,7 @@ import { extract_paths, object } from '../../../../utils/ast.js';
 import * as b from '#compiler/builders';
 import { build_getter } from '../utils.js';
 import { get_value } from './shared/declarations.js';
-import { build_legacy_expression } from './shared/utils.js';
+import { build_legacy_expression_2 } from './shared/utils.js';
 
 /**
  * @param {AST.EachBlock} node
@@ -31,10 +31,14 @@ export function EachBlock(node, context) {
 	};
 	const collection = context.state.analysis.runes
 		? /** @type {Expression} */ (context.visit(node.expression, parent_scope_state))
-		: build_legacy_expression(node.expression, {
+		: build_legacy_expression_2(
+				{
 					...context,
 					state: parent_scope_state
-			});
+				},
+				node.expression,
+				node.metadata.expression
+			);
 
 	if (!each_node_meta.is_controlled) {
 		context.state.template.push_comment();

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

@@ -3,7 +3,7 @@
 /** @import { ComponentContext } from '../types' */
 import { is_ignored } from '../../../../state.js';
 import * as b from '#compiler/builders';
-import { build_legacy_expression } from './shared/utils.js';
+import { build_legacy_expression_2 } from './shared/utils.js';
 
 /**
  * @param {AST.HtmlTag} node
@@ -14,7 +14,7 @@ export function HtmlTag(node, context) {
 
 	const expression = context.state.analysis.runes
 		? /** @type {Expression} */ (context.visit(node.expression))
-		: build_legacy_expression(node.expression, context);
+		: build_legacy_expression_2(context, node.expression, node.metadata.expression);
 
 	const is_svg = context.state.metadata.namespace === 'svg';
 	const is_mathml = context.state.metadata.namespace === 'mathml';

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

@@ -2,7 +2,7 @@
 /** @import { AST } from '#compiler' */
 /** @import { ComponentContext } from '../types' */
 import * as b from '#compiler/builders';
-import { build_legacy_expression } from './shared/utils.js';
+import { build_legacy_expression_2 } from './shared/utils.js';
 
 /**
  * @param {AST.IfBlock} node
@@ -34,7 +34,7 @@ export function IfBlock(node, context) {
 
 	const test = context.state.analysis.runes
 		? /** @type {Expression} */ (context.visit(node.test))
-		: build_legacy_expression(node.test, context);
+		: build_legacy_expression_2(context, node.test, node.metadata.expression);
 
 	/** @type {Expression[]} */
 	const args = [

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

@@ -2,7 +2,7 @@
 /** @import { AST } from '#compiler' */
 /** @import { ComponentContext } from '../types' */
 import * as b from '#compiler/builders';
-import { build_legacy_expression } from './shared/utils.js';
+import { build_legacy_expression_2 } from './shared/utils.js';
 
 /**
  * @param {AST.KeyBlock} node
@@ -13,7 +13,7 @@ export function KeyBlock(node, context) {
 
 	const key = context.state.analysis.runes
 		? /** @type {Expression} */ (context.visit(node.expression))
-		: build_legacy_expression(node.expression, context);
+		: build_legacy_expression_2(context, node.expression, node.metadata.expression);
 	const body = /** @type {Expression} */ (context.visit(node.fragment));
 
 	context.state.init.push(

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

@@ -3,7 +3,7 @@
 /** @import { ComponentContext } from '../types' */
 import { unwrap_optional } from '../../../../utils/ast.js';
 import * as b from '#compiler/builders';
-import { build_legacy_expression } from './shared/utils.js';
+import { build_legacy_expression_2 } from './shared/utils.js';
 
 /**
  * @param {AST.RenderTag} node
@@ -34,7 +34,11 @@ export function RenderTag(node, context) {
 
 	let snippet_function = context.state.analysis.runes
 		? /** @type {Expression} */ (context.visit(callee))
-		: build_legacy_expression(/** @type {Expression} */ (callee), context);
+		: build_legacy_expression_2(
+				context,
+				/** @type {Expression} */ (callee),
+				node.metadata.expression
+			);
 
 	if (node.metadata.dynamic) {
 		// If we have a chain expression then ensure a nullish snippet function gets turned into an empty one

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

@@ -435,6 +435,37 @@ function is_pure_expression(expression) {
 	}
 }
 
+/**
+ *
+ * @param {ComponentContext} context
+ * @param {Expression} expression
+ * @param {ExpressionMetadata} metadata
+ */
+export function build_legacy_expression_2(context, expression, metadata) {
+	const sequence = b.sequence([]);
+
+	for (const binding of metadata.dependencies) {
+		if (binding.kind === 'normal') {
+			continue;
+		}
+
+		var getter = build_getter({ ...binding.node }, context.state);
+
+		if (binding.kind === 'rest_prop') {
+			getter = b.call('Object.keys', getter);
+		} else if (binding.kind === 'bindable_prop') {
+			getter = b.call('$.deep_read_state', getter);
+		}
+
+		sequence.expressions.push(getter);
+	}
+
+	const value = /** @type {Expression} */ (context.visit(expression));
+	sequence.expressions.push(b.call('$.untrack', b.thunk(value)));
+
+	return sequence;
+}
+
 /**
  * Serializes an expression with reactivity like in Svelte 4
  * @param {Expression} expression

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

@@ -135,6 +135,10 @@ export namespace AST {
 	export interface HtmlTag extends BaseNode {
 		type: 'HtmlTag';
 		expression: Expression;
+		/** @internal */
+		metadata: {
+			expression: ExpressionMetadata;
+		};
 	}
 
 	/** An HTML comment */
@@ -151,6 +155,10 @@ export namespace AST {
 		declaration: VariableDeclaration & {
 			declarations: [VariableDeclarator & { id: Pattern; init: Expression }];
 		};
+		/** @internal */
+		metadata: {
+			expression: ExpressionMetadata;
+		};
 	}
 
 	/** A `{@debug ...}` tag */
@@ -165,6 +173,7 @@ export namespace AST {
 		expression: SimpleCallExpression | (ChainExpression & { expression: SimpleCallExpression });
 		/** @internal */
 		metadata: {
+			expression: ExpressionMetadata;
 			dynamic: boolean;
 			arguments: ExpressionMetadata[];
 			path: SvelteNode[];
@@ -447,6 +456,10 @@ export namespace AST {
 		test: Expression;
 		consequent: Fragment;
 		alternate: Fragment | null;
+		/** @internal */
+		metadata: {
+			expression: ExpressionMetadata;
+		};
 	}
 
 	/** An `{#await ...}` block */
@@ -461,12 +474,20 @@ export namespace AST {
 		pending: Fragment | null;
 		then: Fragment | null;
 		catch: Fragment | null;
+		/** @internal */
+		metadata: {
+			expression: ExpressionMetadata;
+		};
 	}
 
 	export interface KeyBlock extends BaseNode {
 		type: 'KeyBlock';
 		expression: Expression;
 		fragment: Fragment;
+		/** @internal */
+		metadata: {
+			expression: ExpressionMetadata;
+		};
 	}
 
 	export interface SnippetBlock extends BaseNode {