chore: remove exposable (#9783)

* use flags for prop_source, this will be useful later

* remove exposable/expose stuff

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>

Author: Rich-Harris

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

@@ -1,6 +1,7 @@
 import * as b from '../../../utils/builders.js';
 import { extract_paths, is_simple_expression } from '../../../utils/ast.js';
 import { error } from '../../../errors.js';
+import { PROPS_CALL_DEFAULT_VALUE, PROPS_IS_IMMUTABLE } from '../../../../constants.js';
 
 /**
  * @template {import('./types').ClientTransformState} State
@@ -359,29 +360,43 @@ export function get_props_method(binding, state, name, default_value) {
 		(state.analysis.immutable ? binding.reassigned : binding.mutated);
 
 	if (needs_source) {
-		args.push(b.literal(state.analysis.immutable));
-	}
+		let flags = 0;
 
-	if (default_value) {
-		// To avoid eagerly evaluating the right-hand-side, we wrap it in a thunk if necessary
-		if (is_simple_expression(default_value)) {
-			args.push(default_value);
-		} else {
-			if (
-				default_value.type === 'CallExpression' &&
-				default_value.callee.type === 'Identifier' &&
-				default_value.arguments.length === 0
-			) {
-				args.push(default_value.callee);
+		/** @type {import('estree').Expression | undefined} */
+		let arg;
+
+		if (state.analysis.immutable) {
+			flags |= PROPS_IS_IMMUTABLE;
+		}
+
+		if (default_value) {
+			// To avoid eagerly evaluating the right-hand-side, we wrap it in a thunk if necessary
+			if (is_simple_expression(default_value)) {
+				arg = default_value;
 			} else {
-				args.push(b.thunk(default_value));
+				if (
+					default_value.type === 'CallExpression' &&
+					default_value.callee.type === 'Identifier' &&
+					default_value.arguments.length === 0
+				) {
+					arg = default_value.callee;
+				} else {
+					arg = b.thunk(default_value);
+				}
+
+				flags |= PROPS_CALL_DEFAULT_VALUE;
 			}
+		}
 
-			args.push(b.true);
+		if (flags || arg) {
+			args.push(b.literal(flags));
+			if (arg) args.push(arg);
 		}
+
+		return b.call('$.prop_source', ...args);
 	}
 
-	return b.call(needs_source ? '$.prop_source' : '$.prop', ...args);
+	return b.call('$.prop', ...args);
 }
 
 /**

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

@@ -795,32 +795,17 @@ function serialize_inline_component(node, component_name, context) {
 				push_prop(
 					b.get(attribute.name, [
 						b.return(
-							b.call(
-								'$.exposable',
-								b.thunk(
-									/** @type {import('estree').Expression} */ (context.visit(attribute.expression))
-								)
-							)
+							/** @type {import('estree').Expression} */ (context.visit(attribute.expression))
 						)
 					])
 				);
-				// If the binding is just a reference to a top level state variable
-				// we don't need a setter as the inner component can write to the signal directly
-				const binding =
-					attribute.expression.type !== 'Identifier'
-						? null
-						: context.state.scope.get(attribute.expression.name);
-				if (
-					binding === null ||
-					(binding.kind !== 'state' && binding.kind !== 'prop' && binding.kind !== 'rest_prop')
-				) {
-					const assignment = b.assignment('=', attribute.expression, b.id('$$value'));
-					push_prop(
-						b.set(attribute.name, [
-							b.stmt(serialize_set_binding(assignment, context, () => context.visit(assignment)))
-						])
-					);
-				}
+
+				const assignment = b.assignment('=', attribute.expression, b.id('$$value'));
+				push_prop(
+					b.set(attribute.name, [
+						b.stmt(serialize_set_binding(assignment, context, () => context.visit(assignment)))
+					])
+				);
 			}
 		}
 	}

packages/svelte/src/constants.js

@@ -5,6 +5,9 @@ export const EACH_IS_CONTROLLED = 1 << 3;
 export const EACH_IS_ANIMATED = 1 << 4;
 export const EACH_IS_IMMUTABLE = 1 << 6;
 
+export const PROPS_IS_IMMUTABLE = 1;
+export const PROPS_CALL_DEFAULT_VALUE = 1 << 1;
+
 /** List of Element events that will be delegated */
 export const DelegatedEvents = [
 	'beforeinput',

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

@@ -34,7 +34,6 @@ import {
 	untrack,
 	effect,
 	flushSync,
-	expose,
 	safe_not_equal,
 	current_block,
 	source,
@@ -1193,10 +1192,7 @@ export function bind_prop(props, prop, value) {
 	/** @param {V | null} value */
 	const update = (value) => {
 		const current_props = unwrap(props);
-		const signal = expose(() => current_props[prop]);
-		if (is_signal(signal)) {
-			set(signal, value);
-		} else if (Object.getOwnPropertyDescriptor(current_props, prop)?.set !== undefined) {
+		if (get_descriptor(current_props, prop)?.set !== undefined) {
 			current_props[prop] = value;
 		}
 	};

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

@@ -1,7 +1,8 @@
 import { DEV } from 'esm-env';
 import { subscribe_to_store } from '../../store/utils.js';
 import { EMPTY_FUNC, run_all } from '../common.js';
-import { get_descriptors, is_array } from './utils.js';
+import { get_descriptor, get_descriptors, is_array } from './utils.js';
+import { PROPS_CALL_DEFAULT_VALUE, PROPS_IS_IMMUTABLE } from '../../constants.js';
 
 export const SOURCE = 1;
 export const DERIVED = 1 << 1;
@@ -30,8 +31,7 @@ let current_scheduler_mode = FLUSH_MICROTASK;
 // Used for handling scheduling
 let is_micro_task_queued = false;
 let is_task_queued = false;
-// Used for exposing signals
-let is_signal_exposed = false;
+
 // Handle effect queues
 
 /** @type {import('./types.js').EffectSignal[]} */
@@ -63,8 +63,6 @@ export let current_untracking = false;
 /** Exists to opt out of the mutation validation for stores which may be set for the first time during a derivation */
 let ignore_mutation_validation = false;
 
-/** @type {null | import('./types.js').Signal} */
-let current_captured_signal = null;
 // If we are working with a get() chain that has no active container,
 // to prevent memory leaks, we skip adding the consumer.
 let current_skip_consumer = false;
@@ -800,23 +798,6 @@ export function unsubscribe_on_destroy(stores) {
 	});
 }
 
-/**
- * Wraps a function and marks execution context so that the last signal read from can be captured
- * using the `expose` function.
- * @template V
- * @param {() => V} fn
- * @returns {V}
- */
-export function exposable(fn) {
-	const previous_is_signal_exposed = is_signal_exposed;
-	try {
-		is_signal_exposed = true;
-		return fn();
-	} finally {
-		is_signal_exposed = previous_is_signal_exposed;
-	}
-}
-
 /**
  * @template V
  * @param {import('./types.js').Signal<V>} signal
@@ -836,10 +817,6 @@ export function get(signal) {
 		return signal.v;
 	}
 
-	if (is_signal_exposed && current_should_capture_signal) {
-		current_captured_signal = signal;
-	}
-
 	if (is_signals_recorded) {
 		captured_signals.add(signal);
 	}
@@ -906,31 +883,6 @@ export function set_sync(signal, value) {
 	flushSync(() => set(signal, value));
 }
 
-/**
- * Invokes a function and captures the last signal that is read during the invocation
- * if that signal is read within the `exposable` function context.
- * If a signal is captured, it returns the signal instead of the read value.
- * @template V
- * @param {() => V} possible_signal_fn
- * @returns {any}
- */
-export function expose(possible_signal_fn) {
-	const previous_captured_signal = current_captured_signal;
-	const previous_should_capture_signal = current_should_capture_signal;
-	current_captured_signal = null;
-	current_should_capture_signal = true;
-	try {
-		const value = possible_signal_fn();
-		if (current_captured_signal === null) {
-			return value;
-		}
-		return current_captured_signal;
-	} finally {
-		current_captured_signal = previous_captured_signal;
-		current_should_capture_signal = previous_should_capture_signal;
-	}
-}
-
 /**
  * Invokes a function and captures all signals that are read during the invocation,
  * then invalidates them.
@@ -1463,35 +1415,19 @@ export function is_store(val) {
  * @template V
  * @param {import('./types.js').MaybeSignal<Record<string, unknown>>} props_obj
  * @param {string} key
- * @param {boolean} immutable
+ * @param {number} flags
  * @param {V | (() => V)} [default_value]
- * @param {boolean} [call_default_value]
  * @returns {import('./types.js').Signal<V> | (() => V)}
  */
-export function prop_source(props_obj, key, immutable, default_value, call_default_value) {
+export function prop_source(props_obj, key, flags, default_value) {
+	const call_default_value = (flags & PROPS_CALL_DEFAULT_VALUE) !== 0;
+	const immutable = (flags & PROPS_IS_IMMUTABLE) !== 0;
+
 	const props = is_signal(props_obj) ? get(props_obj) : props_obj;
-	const possible_signal = /** @type {import('./types.js').MaybeSignal<V>} */ (
-		expose(() => props[key])
-	);
-	const update_bound_prop = Object.getOwnPropertyDescriptor(props, key)?.set;
+	const update_bound_prop = get_descriptor(props, key)?.set;
 	let value = props[key];
 	const should_set_default_value = value === undefined && default_value !== undefined;
 
-	if (
-		is_signal(possible_signal) &&
-		possible_signal.v === value &&
-		update_bound_prop === undefined
-	) {
-		if (should_set_default_value) {
-			set(
-				possible_signal,
-				// @ts-expect-error would need a cumbersome method overload to type this
-				call_default_value ? default_value() : default_value
-			);
-		}
-		return possible_signal;
-	}
-
 	if (should_set_default_value) {
 		value =
 			// @ts-expect-error would need a cumbersome method overload to type this
@@ -1534,7 +1470,7 @@ export function prop_source(props_obj, key, immutable, default_value, call_defau
 		}
 	});
 
-	if (is_signal(possible_signal) && update_bound_prop !== undefined) {
+	if (update_bound_prop !== undefined) {
 		let ignore_first = !should_set_default_value;
 		sync_effect(() => {
 			// Before if to ensure signal dependency is registered
@@ -1548,11 +1484,9 @@ export function prop_source(props_obj, key, immutable, default_value, call_defau
 				return;
 			}
 
-			if (not_equal(immutable, propagating_value, possible_signal.v)) {
-				ignore_next1 = true;
-				did_update_to_defined = true;
-				untrack(() => update_bound_prop(propagating_value));
-			}
+			ignore_next1 = true;
+			did_update_to_defined = true;
+			untrack(() => update_bound_prop(propagating_value));
 		});
 	}
 

packages/svelte/src/internal/index.js

@@ -4,8 +4,6 @@ export {
 	set,
 	set_sync,
 	invalidate_inner_signals,
-	expose,
-	exposable,
 	source,
 	mutable_source,
 	derived,

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

@@ -6,7 +6,7 @@ import * as $ from "svelte/internal";
 export default function Svelte_element($$anchor, $$props) {
 	$.push($$props, true);
 
-	let tag = $.prop_source($$props, "tag", true, 'hr');
+	let tag = $.prop_source($$props, "tag", 1, 'hr');
 	/* Init */
 	var fragment = $.comment($$anchor);
 	var node = $.child_frag(fragment);