fix: ensure #if blocks correctly guard against nullable prop values

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

@@ -54,8 +54,7 @@ export function SlotElement(node, context) {
 	// Let bindings first, they can be used on attributes
 	context.state.init.push(...lets);
 
-	const props_expression =
-		spreads.length === 0 ? b.object(props) : b.call('$.spread_props', b.object(props), ...spreads);
+	const props_expression = b.call('$.props', b.object(props), ...spreads);
 
 	const fallback =
 		node.fragment.nodes.length === 0

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

@@ -4,8 +4,8 @@
 import { dev, is_ignored } from '../../../../../state.js';
 import { get_attribute_chunks, object } from '../../../../../utils/ast.js';
 import * as b from '#compiler/builders';
-import { build_bind_this, memoize_expression, validate_binding } from '../shared/utils.js';
-import { build_attribute_value } from '../shared/element.js';
+import { build_bind_this, memoize_expression, validate_binding } from './utils.js';
+import { build_attribute_value } from './element.js';
 import { build_event_handler } from './events.js';
 import { determine_slot } from '../../../../../utils/slot.js';
 
@@ -399,14 +399,10 @@ export function build_component(node, component_name, context) {
 		push_prop(b.init('$$legacy', b.true));
 	}
 
-	const props_expression =
-		props_and_spreads.length === 0 ||
-		(props_and_spreads.length === 1 && Array.isArray(props_and_spreads[0]))
-			? b.object(/** @type {Property[]} */ (props_and_spreads[0]) || [])
-			: b.call(
-					'$.spread_props',
-					...props_and_spreads.map((p) => (Array.isArray(p) ? b.object(p) : p))
-				);
+	const props_expression = b.call(
+		'$.props',
+		...props_and_spreads.map((p) => (Array.isArray(p) ? b.object(p) : p))
+	);
 
 	/** @param {Expression} node_id */
 	let fn = (node_id) => {

packages/svelte/src/internal/client/context.js

@@ -101,16 +101,15 @@ export function getAllContexts() {
  * @returns {void}
  */
 export function push(props, runes = false, fn) {
-	var ctx = (component_context = {
+	component_context = {
 		p: component_context,
 		c: null,
-		d: false,
 		e: null,
 		m: false,
 		s: props,
 		x: null,
 		l: null
-	});
+	};
 
 	if (legacy_mode_flag && !runes) {
 		component_context.l = {
@@ -121,10 +120,6 @@ export function push(props, runes = false, fn) {
 		};
 	}
 
-	teardown(() => {
-		/** @type {ComponentContext} */ (ctx).d = true;
-	});
-
 	if (DEV) {
 		// component function
 		component_context.function = fn;

packages/svelte/src/internal/client/index.js

@@ -114,7 +114,7 @@ export {
 	prop,
 	rest_props,
 	legacy_rest_props,
-	spread_props,
+	props,
 	update_pre_prop,
 	update_prop
 } from './reactivity/props.js';

packages/svelte/src/internal/client/reactivity/deriveds.js

@@ -116,7 +116,7 @@ let stack = [];
  * @param {Derived} derived
  * @returns {Effect | null}
  */
-function get_derived_parent_effect(derived) {
+export function get_derived_parent_effect(derived) {
 	var parent = derived.parent;
 	while (parent !== null) {
 		if ((parent.f & DERIVED) === 0) {

packages/svelte/src/internal/client/reactivity/props.js

@@ -9,11 +9,17 @@ import {
 } from '../../../constants.js';
 import { get_descriptor, is_function } from '../../shared/utils.js';
 import { mutable_source, set, source, update } from './sources.js';
-import { derived, derived_safe_equal } from './deriveds.js';
-import { get, captured_signals, untrack } from '../runtime.js';
+import { derived, derived_safe_equal, get_derived_parent_effect } from './deriveds.js';
+import { active_effect, captured_signals, get, untrack } from '../runtime.js';
 import { safe_equals } from './equality.js';
 import * as e from '../errors.js';
-import { LEGACY_DERIVED_PROP, LEGACY_PROPS, STATE_SYMBOL } from '#client/constants';
+import {
+	DESTROYED,
+	INERT,
+	LEGACY_DERIVED_PROP,
+	LEGACY_PROPS,
+	STATE_SYMBOL
+} from '#client/constants';
 import { proxy } from '../proxy.js';
 import { capture_store_binding } from './store.js';
 import { legacy_mode_flag } from '../../flags/index.js';
@@ -159,16 +165,17 @@ export function legacy_rest_props(props, exclude) {
  * The proxy handler for spread props. Handles the incoming array of props
  * that looks like `() => { dynamic: props }, { static: prop }, ..` and wraps
  * them so that the whole thing is passed to the component as the `$$props` argument.
- * @template {Record<string | symbol, unknown>} T
- * @type {ProxyHandler<{ props: Array<T | (() => T)> }>}}
+ * @typedef {Record<string | symbol, unknown>} AnyProps
+ * @type {ProxyHandler<{ props: Array<AnyProps | (() => AnyProps)>, old_props: AnyProps, destroyed: boolean }>}}
  */
 const spread_props_handler = {
 	get(target, key) {
+		if (target.destroyed && key in target.old_props) return target.old_props[key];
 		let i = target.props.length;
 		while (i--) {
 			let p = target.props[i];
 			if (is_function(p)) p = p();
-			if (typeof p === 'object' && p !== null && key in p) return p[key];
+			if (typeof p === 'object' && p !== null && key in p) return (target.old_props[key] = p[key]);
 		}
 	},
 	set(target, key, value) {
@@ -178,7 +185,7 @@ const spread_props_handler = {
 			if (is_function(p)) p = p();
 			const desc = get_descriptor(p, key);
 			if (desc && desc.set) {
-				desc.set(value);
+				desc.set((target.old_props[key] = value));
 				return true;
 			}
 		}
@@ -237,16 +244,34 @@ const spread_props_handler = {
  * @param {Array<Record<string, unknown> | (() => Record<string, unknown>)>} props
  * @returns {any}
  */
-export function spread_props(...props) {
-	return new Proxy({ props }, spread_props_handler);
+export function props(...props) {
+	const effect = active_effect;
+	return new Proxy(
+		{
+			props,
+			old_props: untrack(() => {
+				const old_props = {};
+				for (let p of props) {
+					if (typeof p === 'function') p = p();
+					Object.assign(old_props, p);
+				}
+				return old_props;
+			}),
+			get destroyed() {
+				return effect ? (effect.f & (DESTROYED | INERT)) !== 0 : false;
+			}
+		},
+		spread_props_handler
+	);
 }
 
 /**
- * @param {Derived} current_value
- * @returns {boolean}
+ * @param {Derived} derived
  */
-function has_destroyed_component_ctx(current_value) {
-	return current_value.ctx?.d ?? false;
+function is_paused_or_destroyed(derived) {
+	const parent = get_derived_parent_effect(derived);
+	if (!parent) return false;
+	return (parent.f & (DESTROYED | INERT)) !== 0;
 }
 
 /**
@@ -414,7 +439,7 @@ export function prop(props, key, flags, fallback) {
 					fallback_value = new_value;
 				}
 
-				if (has_destroyed_component_ctx(current_value)) {
+				if (is_paused_or_destroyed(current_value)) {
 					return value;
 				}
 
@@ -424,7 +449,7 @@ export function prop(props, key, flags, fallback) {
 			return value;
 		}
 
-		if (has_destroyed_component_ctx(current_value)) {
+		if (is_paused_or_destroyed(current_value)) {
 			return current_value.v;
 		}
 

packages/svelte/src/internal/client/reactivity/sources.js

@@ -14,7 +14,6 @@ import {
 	reaction_sources,
 	check_dirtiness,
 	untracking,
-	is_destroying_effect,
 	push_reaction_value
 } from '../runtime.js';
 import { equals, safe_equals } from './equality.js';
@@ -38,9 +37,6 @@ import { execute_derived } from './deriveds.js';
 
 export let inspect_effects = new Set();
 
-/** @type {Map<Source, any>} */
-export const old_values = new Map();
-
 /**
  * @param {Set<any>} v
  */
@@ -160,14 +156,6 @@ export function set(source, value, should_proxy = false) {
  */
 export function internal_set(source, value) {
 	if (!source.equals(value)) {
-		var old_value = source.v;
-
-		if (is_destroying_effect) {
-			old_values.set(source, value);
-		} else {
-			old_values.set(source, old_value);
-		}
-
 		source.v = value;
 
 		if (DEV && tracing_mode_flag) {

packages/svelte/src/internal/client/runtime.js

@@ -25,7 +25,7 @@ import {
 	EFFECT_IS_UPDATING
 } from './constants.js';
 import { flush_tasks } from './dom/task.js';
-import { internal_set, old_values } from './reactivity/sources.js';
+import { internal_set } from './reactivity/sources.js';
 import { destroy_derived_effects, update_derived } from './reactivity/deriveds.js';
 import * as e from './errors.js';
 
@@ -535,7 +535,6 @@ function flush_queued_root_effects() {
 				var collected_effects = process_effects(root_effects[i]);
 				flush_queued_effects(collected_effects);
 			}
-			old_values.clear();
 		}
 	} finally {
 		is_flushing = false;
@@ -800,10 +799,6 @@ export function get(signal) {
 		}
 	}
 
-	if (is_destroying_effect && old_values.has(signal)) {
-		return old_values.get(signal);
-	}
-
 	return signal.v;
 }
 

packages/svelte/src/internal/client/types.d.ts

@@ -14,8 +14,6 @@ export type ComponentContext = {
 	p: null | ComponentContext;
 	/** context */
 	c: null | Map<unknown, unknown>;
-	/** destroyed */
-	d: boolean;
 	/** deferred effects */
 	e: null | Array<{
 		fn: () => void | (() => void);

packages/svelte/tests/runtime-runes/samples/effect-teardown-stale-value/_config.js

@@ -14,7 +14,8 @@ export default test({
 			'up',
 			{ foo: false, bar: false },
 			'down',
-			{ foo: false, bar: false },
+			// TODO the test should be deleted as there's no more concept of "teardown stale value"
+			{ foo: true, bar: true },
 			'up',
 			{ foo: true, bar: true }
 		]);

packages/svelte/tests/runtime-runes/samples/nested-effect-conflict/_config.js

@@ -10,6 +10,14 @@ export default test({
 		});
 
 		await Promise.resolve();
-		assert.deepEqual(logs, ['top level', 'inner', 0, 'destroy inner', 0, 'destroy outer', 0]);
+		assert.deepEqual(logs, [
+			'top level',
+			'inner',
+			0,
+			'destroy inner',
+			undefined,
+			'destroy outer',
+			undefined
+		]);
 	}
 });

packages/svelte/tests/snapshot/samples/bind-component-snippet/_expected/client/index.svelte.js

@@ -18,17 +18,17 @@ export default function Bind_component_snippet($$anchor) {
 	var fragment = root();
 	var node = $.first_child(fragment);
 
-	TextInput(node, {
+	TextInput(node, $.props({
 		get value() {
 			return $.get(value);
 		},
 		set value($$value) {
 			$.set(value, $$value, true);
 		}
-	});
+	}));
 
 	var text_1 = $.sibling(node);
 
 	$.template_effect(() => $.set_text(text_1, ` value: ${$.get(value) ?? ''}`));
 	$.append($$anchor, fragment);
-}
+}

packages/svelte/tests/snapshot/samples/bind-this/_expected/client/index.svelte.js

@@ -3,5 +3,5 @@ import 'svelte/internal/flags/legacy';
 import * as $ from 'svelte/internal/client';
 
 export default function Bind_this($$anchor) {
-	$.bind_this(Foo($$anchor, { $$legacy: true }), ($$value) => foo = $$value, () => foo);
-}
+	$.bind_this(Foo($$anchor, $.props({ $$legacy: true })), ($$value) => foo = $$value, () => foo);
+}

packages/svelte/tests/snapshot/samples/function-prop-no-getter/_expected/client/index.svelte.js

@@ -10,7 +10,7 @@ export default function Function_prop_no_getter($$anchor) {
 
 	const plusOne = (num) => num + 1;
 
-	Button($$anchor, {
+	Button($$anchor, $.props({
 		onmousedown: () => $.set(count, $.get(count) + 1),
 		onmouseup,
 		onmouseenter: () => $.set(count, plusOne($.get(count)), true),
@@ -23,5 +23,5 @@ export default function Function_prop_no_getter($$anchor) {
 			$.append($$anchor, text);
 		},
 		$$slots: { default: true }
-	});
-}
+	}));
+}

packages/svelte/tests/snapshot/samples/purity/_expected/client/index.svelte.js

@@ -16,6 +16,6 @@ export default function Purity($$anchor) {
 
 	var node = $.sibling(p_1, 2);
 
-	Child(node, { prop: encodeURIComponent('hello') });
+	Child(node, $.props({ prop: encodeURIComponent('hello') }));
 	$.append($$anchor, fragment);
-}
+}