fix: widen ownership when calling setContext

Instead of doing ownership addition at each `getContext` call site, we do it once as the `setContext` call site and make the state basically global.
- avoids potential false positives in edge cases
- makes the whole thing more performant, especially around things like calling `getContext` inside a list item component
- false negatives are unlikely from this

fixes #15072

Author: dummdidumm

.changeset/unlucky-gorillas-hunt.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: widen ownership when calling setContext

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

@@ -8,7 +8,8 @@ import {
 	active_effect,
 	active_reaction,
 	set_active_effect,
-	set_active_reaction
+	set_active_reaction,
+	untrack
 } from './runtime.js';
 import { effect } from './reactivity/effects.js';
 import { legacy_mode_flag } from '../flags/index.js';
@@ -49,14 +50,6 @@ export function set_dev_current_component_function(fn) {
 export function getContext(key) {
 	const context_map = get_or_init_context_map('getContext');
 	const result = /** @type {T} */ (context_map.get(key));
-
-	if (DEV) {
-		const fn = /** @type {ComponentContext} */ (component_context).function;
-		if (fn) {
-			add_owner(result, fn, true);
-		}
-	}
-
 	return result;
 }
 
@@ -74,6 +67,15 @@ export function getContext(key) {
  */
 export function setContext(key, context) {
 	const context_map = get_or_init_context_map('setContext');
+
+	if (DEV) {
+		// When state is put into context, we treat as if it's global from now on.
+		// We do for performance reasons (it's for example very expensive to call
+		// getContext on a big object many times when part of a list component)
+		// and danger of false positives.
+		untrack(() => add_owner(context, null, true));
+	}
+
 	context_map.set(key, context);
 	return context;
 }
@@ -100,16 +102,6 @@ export function hasContext(key) {
  */
 export function getAllContexts() {
 	const context_map = get_or_init_context_map('getAllContexts');
-
-	if (DEV) {
-		const fn = component_context?.function;
-		if (fn) {
-			for (const value of context_map.values()) {
-				add_owner(value, fn, true);
-			}
-		}
-	}
-
 	return /** @type {T} */ (context_map);
 }
 

packages/svelte/src/internal/client/dev/ownership.js

@@ -109,7 +109,7 @@ export function mark_module_end(component) {
 
 /**
  * @param {any} object
- * @param {any} owner
+ * @param {any | null} owner
  * @param {boolean} [global]
  * @param {boolean} [skip_warning]
  */
@@ -120,7 +120,7 @@ export function add_owner(object, owner, global = false, skip_warning = false) {
 		if (metadata && !has_owner(metadata, component)) {
 			let original = get_owner(metadata);
 
-			if (owner[FILENAME] !== component[FILENAME] && !skip_warning) {
+			if (owner && owner[FILENAME] !== component[FILENAME] && !skip_warning) {
 				w.ownership_invalid_binding(component[FILENAME], owner[FILENAME], original[FILENAME]);
 			}
 		}
@@ -165,7 +165,7 @@ export function widen_ownership(from, to) {
 
 /**
  * @param {any} object
- * @param {Function} owner
+ * @param {Function | null} owner If `null`, then the object is globally owned and will not be checked
  * @param {Set<any>} seen
  */
 function add_owner_to_object(object, owner, seen) {
@@ -174,7 +174,11 @@ function add_owner_to_object(object, owner, seen) {
 	if (metadata) {
 		// this is a state proxy, add owner directly, if not globally shared
 		if ('owners' in metadata && metadata.owners != null) {
-			metadata.owners.add(owner);
+			if (owner) {
+				metadata.owners.add(owner);
+			} else {
+				metadata.owners = null;
+			}
 		}
 	} else if (object && typeof object === 'object') {
 		if (seen.has(object)) return;