merge main

Author: Rich-Harris

.changeset/dirty-pianos-sparkle.md

@@ -0,0 +1,5 @@
+---
+'svelte': minor
+---
+
+feat: allow state created in deriveds/effects to be written/read locally without self-invalidation

benchmarking/compare/index.js

@@ -2,7 +2,6 @@ import fs from 'node:fs';
 import path from 'node:path';
 import { execSync, fork } from 'node:child_process';
 import { fileURLToPath } from 'node:url';
-import { benchmarks } from '../benchmarks.js';
 
 // if (execSync('git status --porcelain').toString().trim()) {
 // 	console.error('Working directory is not clean');

benchmarking/compare/runner.js

@@ -1,7 +1,7 @@
-import { benchmarks } from '../benchmarks.js';
+import { reactivity_benchmarks } from '../benchmarks/reactivity/index.js';
 
 const results = [];
-for (const benchmark of benchmarks) {
+for (const benchmark of reactivity_benchmarks) {
 	const result = await benchmark();
 	console.error(result.benchmark);
 	results.push(result);

documentation/docs/98-reference/.generated/client-errors.md

@@ -122,12 +122,6 @@ Property descriptors defined on `$state` objects must contain `value` and always
 Cannot set prototype of `$state` object
 ```
 
-### state_unsafe_local_read
-
-```
-Reading state that was created inside the same derived is forbidden. Consider using `untrack` to read locally created state
-```
-
 ### state_unsafe_mutation
 
 ```

packages/svelte/messages/client-errors/errors.md

@@ -80,10 +80,6 @@ See the [migration guide](/docs/svelte/v5-migration-guide#Components-are-no-long
 
 > Cannot set prototype of `$state` object
 
-## state_unsafe_local_read
-
-> Reading state that was created inside the same derived is forbidden. Consider using `untrack` to read locally created state
-
 ## state_unsafe_mutation
 
 > Updating state inside a derived or a template expression is forbidden. If the value should not be reactive, declare it without `$state`

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

@@ -219,7 +219,10 @@ export function client_component(analysis, options) {
 	for (const [name, binding] of analysis.instance.scope.declarations) {
 		if (binding.kind === 'legacy_reactive') {
 			legacy_reactive_declarations.push(
-				b.const(name, b.call('$.mutable_state', undefined, analysis.immutable ? b.true : undefined))
+				b.const(
+					name,
+					b.call('$.mutable_source', undefined, analysis.immutable ? b.true : undefined)
+				)
 			);
 		}
 		if (binding.kind === 'store_sub') {

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

@@ -69,14 +69,7 @@ function build_assignment(operator, left, right, context) {
 				is_non_coercive_operator(operator) &&
 				should_proxy(value, context.state.scope);
 
-			return b.call(
-				// inside the constructor, we use `$.simple_set` rather than using `$.set`,
-				// that only assign the value and eventually call onchange since nothing is tracking the signal at this point
-				context.state.in_constructor ? '$.simple_set' : '$.set',
-				left,
-				value,
-				needs_proxy && b.true
-			);
+			return b.call('$.set', left, value, needs_proxy && b.true);
 		}
 	}
 

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

@@ -305,7 +305,7 @@ function create_state_declarators(declarator, { scope, analysis }, value) {
 		return [
 			b.declarator(
 				declarator.id,
-				b.call('$.mutable_state', value, analysis.immutable ? b.true : undefined)
+				b.call('$.mutable_source', value, analysis.immutable ? b.true : undefined)
 			)
 		];
 	}
@@ -320,7 +320,7 @@ function create_state_declarators(declarator, { scope, analysis }, value) {
 			return b.declarator(
 				path.node,
 				binding?.kind === 'state'
-					? b.call('$.mutable_state', value, analysis.immutable ? b.true : undefined)
+					? b.call('$.mutable_source', value, analysis.immutable ? b.true : undefined)
 					: value
 			);
 		})

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

@@ -20,6 +20,7 @@ export const LEGACY_DERIVED_PROP = 1 << 17;
 export const INSPECT_EFFECT = 1 << 18;
 export const HEAD_EFFECT = 1 << 19;
 export const EFFECT_HAS_DERIVED = 1 << 20;
+export const EFFECT_IS_UPDATING = 1 << 21;
 
 export const STATE_SYMBOL = Symbol('$state');
 export const PROXY_ONCHANGE_SYMBOL = Symbol('proxy onchange');

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

@@ -307,21 +307,6 @@ export function state_prototype_fixed() {
 	}
 }
 
-/**
- * Reading state that was created inside the same derived is forbidden. Consider using `untrack` to read locally created state
- * @returns {never}
- */
-export function state_unsafe_local_read() {
-	if (DEV) {
-		const error = new Error(`state_unsafe_local_read\nReading state that was created inside the same derived is forbidden. Consider using \`untrack\` to read locally created state\nhttps://svelte.dev/e/state_unsafe_local_read`);
-
-		error.name = 'Svelte error';
-		throw error;
-	} else {
-		throw new Error(`https://svelte.dev/e/state_unsafe_local_read`);
-	}
-}
-
 /**
  * Updating state inside a derived or a template expression is forbidden. If the value should not be reactive, declare it without `$state`
  * @returns {never}