fix: always allow setContext before first await in component

The previous check was flawed because EFFECT_RAN would be set by the time it is checked, since a promise in a parent component will cause a delay of the inner component being instantiated. Instead we have a new field on the component context checking if the component was already popped (if se we are indeed too late). Don't love it to have a field just for this but I don't see another way to reliably check it.

Fixes #16629

Author: dummdidumm

.changeset/itchy-hats-study.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: always allow `setContext` before first await in component

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

@@ -13,6 +13,7 @@ export const INERT = 1 << 13;
 export const DESTROYED = 1 << 14;
 
 // Flags exclusive to effects
+/** Set once an effect that should run synchronously has run */
 export const EFFECT_RAN = 1 << 15;
 /**
  * 'Transparent' effects do not create a transition boundary.

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

@@ -128,7 +128,11 @@ export function setContext(key, context) {
 
 	if (async_mode_flag) {
 		var flags = /** @type {Effect} */ (active_effect).f;
-		var valid = !active_reaction && (flags & BRANCH_EFFECT) !== 0 && (flags & EFFECT_RAN) === 0;
+		var valid =
+			!active_reaction &&
+			(flags & BRANCH_EFFECT) !== 0 &&
+			// pop() runs synchronously, so this indicates we're setting context after an await
+			!(/** @type {ComponentContext} */ (component_context).i);
 
 		if (!valid) {
 			e.set_context_after_init();
@@ -173,6 +177,7 @@ export function getAllContexts() {
 export function push(props, runes = false, fn) {
 	component_context = {
 		p: component_context,
+		i: false,
 		c: null,
 		e: null,
 		s: props,
@@ -208,6 +213,8 @@ export function pop(component) {
 		context.x = component;
 	}
 
+	context.i = true;
+
 	component_context = context.p;
 
 	if (DEV) {

packages/svelte/src/internal/client/error-handling.js

@@ -29,7 +29,7 @@ export function handle_error(error) {
 		// if the error occurred while creating this subtree, we let it
 		// bubble up until it hits a boundary that can handle it
 		if ((effect.f & BOUNDARY_EFFECT) === 0) {
-			if (!effect.parent && error instanceof Error) {
+			if (DEV && !effect.parent && error instanceof Error) {
 				apply_adjustments(error);
 			}
 
@@ -61,7 +61,7 @@ export function invoke_error_boundary(error, effect) {
 		effect = effect.parent;
 	}
 
-	if (error instanceof Error) {
+	if (DEV && error instanceof Error) {
 		apply_adjustments(error);
 	}
 

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

@@ -1,6 +1,6 @@
 import type { Store } from '#shared';
 import { STATE_SYMBOL } from './constants.js';
-import type { Effect, Source, Value, Reaction } from './reactivity/types.js';
+import type { Effect, Source, Value } from './reactivity/types.js';
 
 type EventCallback = (event: Event) => boolean;
 export type EventCallbackMap = Record<string, EventCallback | EventCallback[]>;
@@ -16,6 +16,8 @@ export type ComponentContext = {
 	c: null | Map<unknown, unknown>;
 	/** deferred effects */
 	e: null | Array<() => void | (() => void)>;
+	/** True if initialized, i.e. pop() ran */
+	i: boolean;
 	/**
 	 * props — needed for legacy mode lifecycle functions, and for `createEventDispatcher`
 	 * @deprecated remove in 6.0

packages/svelte/tests/runtime-runes/samples/async-context-throws-after-await/_config.js

@@ -0,0 +1,11 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	mode: ['client'],
+	async test() {
+		// else runtime_error is checked too soon
+		await tick();
+	},
+	runtime_error: 'set_context_after_init'
+});

packages/svelte/tests/runtime-runes/samples/async-context-throws-after-await/main.svelte

@@ -0,0 +1,7 @@
+<script>
+	import { setContext } from 'svelte';
+
+	await Promise.resolve('hi');
+
+	setContext('key', 'value');
+</script>

packages/svelte/tests/runtime-runes/samples/async-set-context/Inner.svelte

@@ -0,0 +1,7 @@
+<script lang="ts">
+	import { getContext } from "svelte";
+
+  let greeting = getContext("greeting");
+</script>
+
+<p>{greeting}</p>

packages/svelte/tests/runtime-runes/samples/async-set-context/Outer.svelte

@@ -0,0 +1,9 @@
+<script lang="ts">
+	import { setContext } from "svelte";
+	import Inner from "./Inner.svelte";
+
+	setContext("greeting", "hi");
+	await Promise.resolve();
+</script>
+
+<Inner />

packages/svelte/tests/runtime-runes/samples/async-set-context/_config.js

@@ -0,0 +1,11 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	mode: ['client', 'async-server'],
+	ssrHtml: `<p>hi</p>`,
+	async test({ assert, target }) {
+		await tick();
+		assert.htmlEqual(target.innerHTML, '<p>hi</p>');
+	}
+});