alternative approach

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

@@ -1,8 +1,6 @@
-/** @import { ArrowFunctionExpression, BlockStatement, FunctionExpression, Node, Pattern } from 'estree' */
+/** @import { ArrowFunctionExpression, FunctionExpression, Node } from 'estree' */
 /** @import { ComponentContext } from '../../types' */
 import { build_hoisted_params } from '../../utils.js';
-import * as b from '../../../../../utils/builders.js';
-import { walk } from 'zimmerframe';
 
 /**
  * @param {ArrowFunctionExpression | FunctionExpression} node
@@ -12,27 +10,10 @@ export const visit_function = (node, context) => {
 	const metadata = node.metadata;
 
 	let state = { ...context.state, in_constructor: false };
-	let in_constructor = false;
-	let has_super_call = false;
 
 	if (node.type === 'FunctionExpression') {
 		const parent = /** @type {Node} */ (context.path.at(-1));
-		in_constructor = state.in_constructor =
-			parent.type === 'MethodDefinition' && parent.kind === 'constructor';
-
-		// We might not use runes in the immediate class, but we do in the extended class
-		// so we need to inject the enter/leave logic in this constructor if it does a super()
-		// call
-		if (in_constructor) {
-			walk(node.body, null, {
-				// @ts-expect-error
-				CallExpression(node) {
-					if (node.callee.type === 'Super') {
-						has_super_call = true;
-					}
-				}
-			});
-		}
+		state.in_constructor = parent.type === 'MethodDefinition' && parent.kind === 'constructor';
 	}
 
 	if (metadata?.hoisted === true) {
@@ -45,25 +26,5 @@ export const visit_function = (node, context) => {
 		});
 	}
 
-	if (
-		state.analysis.runes &&
-		in_constructor &&
-		(has_super_call || state.private_state.size > 0 || state.public_state.size > 0)
-	) {
-		const params = /** @type {Pattern[]} */ (node.params.map((p) => context.visit(p, state)));
-		const body = /** @type {BlockStatement} */ (context.visit(node.body, state));
-		const enter = b.var('$$', b.call('$.enter_constructor'));
-		const leave = b.stmt(b.call('$.leave_constructor', b.id('$$')));
-
-		body.body.splice(0, 0, enter);
-		body.body.push(leave);
-
-		return {
-			...node,
-			params,
-			body
-		};
-	} else {
-		context.next(state);
-	}
+	context.next(state);
 };

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

@@ -105,14 +105,7 @@ export {
 	user_effect,
 	user_pre_effect
 } from './reactivity/effects.js';
-export {
-	mutable_source,
-	mutate,
-	source,
-	set,
-	enter_constructor,
-	leave_constructor
-} from './reactivity/sources.js';
+export { mutable_source, mutate, source, set } from './reactivity/sources.js';
 export {
 	prop,
 	rest_props,

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

@@ -1,4 +1,4 @@
-/** @import { Derived } from '#client' */
+/** @import { Derived, Source } from '#client' */
 import { DEV } from 'esm-env';
 import { CLEAN, DERIVED, DESTROYED, DIRTY, MAYBE_DIRTY, UNOWNED } from '../constants.js';
 import {
@@ -14,6 +14,20 @@ import {
 import { equals, safe_equals } from './equality.js';
 import * as e from '../errors.js';
 
+/**
+ * When sources are created within a derived, we record them so that we can safely allow
+ * local mutations to these sources without the side-effect error being invoked unnecessarily.
+ * @type {null | Source[]}
+ */
+export let derived_sources = null;
+
+/**
+ * @param {Source[] | null} sources
+ */
+export function set_derived_sources(sources) {
+	derived_sources = sources;
+}
+
 /**
  * @template V
  * @param {() => V} fn
@@ -108,7 +122,13 @@ export function update_derived(derived) {
 		}
 	} else {
 		destroy_derived_children(derived);
-		value = update_reaction(derived);
+		const prev_derived_sources = derived_sources;
+		derived_sources = null;
+		try {
+			value = update_reaction(derived);
+		} finally {
+			derived_sources = prev_derived_sources;
+		}
 	}
 
 	var status =

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

@@ -1,4 +1,4 @@
-/** @import { Derived, Effect, Source, Value, Reaction } from '#client' */
+/** @import { Derived, Effect, Source, Value } from '#client' */
 import { DEV } from 'esm-env';
 import {
 	current_component_context,
@@ -26,16 +26,9 @@ import {
 	MAYBE_DIRTY
 } from '../constants.js';
 import * as e from '../errors.js';
+import { derived_sources, set_derived_sources } from './deriveds.js';
 
 let inspect_effects = new Set();
-/**
- * When we enter a class constructor, we set `constructor_reaction` and then reset it when we leave the
- * constructor. When setting source signals, we avoid firing the mutations inside derived error if the derived
- * reaction matches `constructor_reaction`.
- *
- * @type {Reaction | null}
- * */
-let constructor_reaction = null;
 
 /**
  * @template V
@@ -44,13 +37,21 @@ let constructor_reaction = null;
  */
 /*#__NO_SIDE_EFFECTS__*/
 export function source(v) {
-	return {
+	var source = {
 		f: 0, // TODO ideally we could skip this altogether, but it causes type errors
 		v,
 		reactions: null,
 		equals,
 		version: 0
 	};
+	if (current_reaction !== null && (current_reaction.f & DERIVED) !== 0) {
+		if (derived_sources === null) {
+			set_derived_sources([source]);
+		} else {
+			derived_sources.push(source);
+		}
+	}
+	return source;
 }
 
 /**
@@ -94,9 +95,11 @@ export function mutate(source, value) {
 export function set(source, value) {
 	if (
 		current_reaction !== null &&
-		current_reaction !== constructor_reaction &&
 		is_runes() &&
-		(current_reaction.f & DERIVED) !== 0
+		(current_reaction.f & DERIVED) !== 0 &&
+		// If the source was created locally within the current derived, then
+		// we allow the mutation.
+		(derived_sources === null || !derived_sources.includes(source))
 	) {
 		e.state_unsafe_mutation();
 	}
@@ -182,16 +185,3 @@ function mark_reactions(signal, status) {
 		}
 	}
 }
-
-export function enter_constructor() {
-	const prev = constructor_reaction;
-	constructor_reaction = current_reaction;
-	return prev;
-}
-
-/**
- * @param {Reaction | null} reaction
- */
-export function leave_constructor(reaction) {
-	constructor_reaction = reaction;
-}

packages/svelte/tests/parser-legacy/samples/action-duplicate/output.json

@@ -31,4 +31,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/action-with-call/output.json

@@ -73,4 +73,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/action-with-identifier/output.json

@@ -38,4 +38,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/action-with-literal/output.json

@@ -39,4 +39,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/action/output.json

@@ -23,4 +23,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/animation/output.json

@@ -88,4 +88,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-class-directive/output.json

@@ -38,4 +38,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-containing-solidus/output.json

@@ -38,4 +38,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-curly-bracket/output.json

@@ -52,4 +52,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-dynamic-boolean/output.json

@@ -44,4 +44,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-dynamic/output.json

@@ -80,4 +80,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-empty/output.json

@@ -105,4 +105,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-escaped/output.json

@@ -30,4 +30,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-multiple/output.json

@@ -45,4 +45,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-shorthand/output.json

@@ -34,4 +34,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-static-boolean/output.json

@@ -22,4 +22,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-static/output.json

@@ -30,4 +30,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-style-directive-modifiers/output.json

@@ -15,7 +15,9 @@
 						"end": 36,
 						"type": "StyleDirective",
 						"name": "color",
-						"modifiers": ["important"],
+						"modifiers": [
+							"important"
+						],
 						"value": [
 							{
 								"type": "MustacheTag",
@@ -45,4 +47,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-style-directive-shorthand/output.json

@@ -23,4 +23,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-style-directive-string/output.json

@@ -359,4 +359,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-style-directive/output.json

@@ -45,4 +45,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-style/output.json

@@ -38,4 +38,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-unquoted/output.json

@@ -30,4 +30,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/attribute-with-whitespace/output.json

@@ -46,4 +46,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/await-catch/output.json

@@ -183,4 +183,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/await-then-catch/output.json

@@ -252,4 +252,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/binding-shorthand/output.json

@@ -109,4 +109,4 @@
 			"sourceType": "module"
 		}
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/binding/output.json

@@ -119,4 +119,4 @@
 			"sourceType": "module"
 		}
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/comment-with-ignores/output.json

@@ -9,8 +9,11 @@
 				"start": 0,
 				"end": 31,
 				"data": " svelte-ignore foo, bar ",
-				"ignores": ["foo", "bar"]
+				"ignores": [
+					"foo",
+					"bar"
+				]
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/comment/output.json

@@ -13,4 +13,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/component-dynamic/output.json

@@ -77,4 +77,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/convert-entities-in-element/output.json

@@ -22,4 +22,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/convert-entities/output.json

@@ -13,4 +13,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/css/output.json

@@ -82,4 +82,4 @@
 			"comment": null
 		}
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/dynamic-element-string/output.json

@@ -171,4 +171,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/dynamic-element-variable/output.json

@@ -77,4 +77,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/dynamic-import/output.json

@@ -479,4 +479,4 @@
 			"sourceType": "module"
 		}
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/each-block-destructured/output.json

@@ -265,4 +265,4 @@
 			"sourceType": "module"
 		}
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/each-block-else/output.json

@@ -100,4 +100,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/each-block-indexed/output.json

@@ -106,4 +106,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/each-block-keyed/output.json

@@ -126,4 +126,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/each-block/output.json

@@ -77,4 +77,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/element-with-attribute-empty-string/output.json

@@ -61,4 +61,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/element-with-attribute/output.json

@@ -61,4 +61,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/element-with-mustache/output.json

@@ -50,4 +50,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/element-with-text/output.json

@@ -22,4 +22,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/elements/output.json

@@ -22,4 +22,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/event-handler/output.json

@@ -161,4 +161,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/if-block-else/output.json

@@ -68,4 +68,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/if-block-elseif/output.json

@@ -221,4 +221,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/if-block/output.json

@@ -36,4 +36,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/implicitly-closed-li/output.json

@@ -70,4 +70,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/javascript-comments/output.json

@@ -869,4 +869,4 @@
 			"sourceType": "module"
 		}
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/nbsp/output.json

@@ -22,4 +22,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/no-error-if-before-closing/output.json

@@ -289,4 +289,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/raw-mustaches/output.json

@@ -78,4 +78,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/refs/output.json

@@ -119,4 +119,4 @@
 			"sourceType": "module"
 		}
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/script-attribute-with-curly-braces/output.json

@@ -147,4 +147,4 @@
 			"sourceType": "module"
 		}
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/script-comment-only/output.json

@@ -52,4 +52,4 @@
 			]
 		}
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/script-context-module-unquoted/output.json

@@ -175,4 +175,4 @@
 			"sourceType": "module"
 		}
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/script/output.json

@@ -147,4 +147,4 @@
 			"sourceType": "module"
 		}
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/self-closing-element/output.json

@@ -14,4 +14,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/self-reference/output.json

@@ -133,4 +133,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/slotted-element/output.json

@@ -39,4 +39,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/space-between-mustaches/output.json

@@ -106,4 +106,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/spread/output.json

@@ -36,4 +36,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/style-inside-head/output.json

@@ -30,4 +30,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/textarea-children/output.json

@@ -50,4 +50,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/textarea-end-tag/output.json

@@ -50,4 +50,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/transition-intro-no-params/output.json

@@ -33,4 +33,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/transition-intro/output.json

@@ -101,4 +101,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/unusual-identifier/output.json

@@ -77,4 +77,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/whitespace-after-script-tag/output.json

@@ -147,4 +147,4 @@
 			"sourceType": "module"
 		}
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/whitespace-after-style-tag/output.json

@@ -82,4 +82,4 @@
 			"comment": null
 		}
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/whitespace-leading-trailing/output.json

@@ -29,4 +29,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-legacy/samples/whitespace-normal/output.json

@@ -75,4 +75,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-modern/samples/comment-before-script/output.json

@@ -150,4 +150,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-modern/samples/css-nth-syntax/output.json

@@ -1114,4 +1114,4 @@
 		]
 	},
 	"options": null
-}
+}

packages/svelte/tests/parser-modern/samples/css-pseudo-classes/output.json

@@ -406,4 +406,4 @@
 		"nodes": []
 	},
 	"options": null
-}
+}

packages/svelte/tests/parser-modern/samples/each-block-object-pattern/output.json

@@ -311,4 +311,4 @@
 		]
 	},
 	"options": null
-}
+}

packages/svelte/tests/parser-modern/samples/if-block-else/output.json

@@ -108,4 +108,4 @@
 		]
 	},
 	"options": null
-}
+}

packages/svelte/tests/parser-modern/samples/if-block-elseif/output.json

@@ -202,4 +202,4 @@
 		]
 	},
 	"options": null
-}
+}

packages/svelte/tests/parser-modern/samples/if-block/output.json

@@ -45,4 +45,4 @@
 		]
 	},
 	"options": null
-}
+}

packages/svelte/tests/parser-modern/samples/options/output.json

@@ -178,4 +178,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-modern/samples/semicolon-inside-quotes/output.json

@@ -111,4 +111,4 @@
 		]
 	},
 	"options": null
-}
+}

packages/svelte/tests/parser-modern/samples/snippets/output.json

@@ -230,4 +230,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/parser-modern/samples/template-shadowroot/output.json

@@ -149,4 +149,4 @@
 		]
 	},
 	"options": null
-}
+}

packages/svelte/tests/parser-modern/samples/typescript-in-event-handler/output.json

@@ -497,4 +497,4 @@
 			}
 		]
 	}
-}
+}

packages/svelte/tests/snapshot/samples/class-state-field-constructor-assignment/_expected/client/index.svelte.js

@@ -18,11 +18,8 @@ export default function Class_state_field_constructor_assignment($$anchor, $$pro
 		#b = $.source();
 
 		constructor() {
-			var $$ = $.enter_constructor();
-
 			this.a = 1;
 			this.#b.v = 2;
-			$.leave_constructor($$);
 		}
 	}