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fix: correctly transform {@const foo = await ...} #16463

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fix: correctly transform {@const foo = await ...} #16463

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9905a6b
fix: correctly transform `{@const foo = await ...}`
Ocean-OS Jul 21, 2025
d9db9e3
fix
Ocean-OS Jul 21, 2025
69f1ed8
wrap in async derived instead of derived
Ocean-OS Jul 21, 2025
2e15163
doh
Ocean-OS Jul 21, 2025
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5 changes: 5 additions & 0 deletions .changeset/fluffy-ducks-happen.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'svelte': patch
---

fix: correctly transform `{@const foo = await ...}`
7 changes: 5 additions & 2 deletions packages/svelte/src/compiler/phases/3-transform/client/utils.js
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Original file line number Diff line number Diff line change
Expand Up @@ -291,6 +291,9 @@ export function should_proxy(node, scope) {
* @param {ComponentClientTransformState} state
* @param {Expression} arg
*/
export function create_derived(state, arg) {
return b.call(state.analysis.runes ? '$.derived' : '$.derived_safe_equal', arg);
export function create_derived(state, arg, async = false) {
return b.call(
state.analysis.runes ? `$.${async ? 'async_' : ''}derived` : '$.derived_safe_equal',
arg
);
}
13 changes: 9 additions & 4 deletions packages/svelte/src/compiler/phases/3-transform/client/visitors/ConstTag.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@
/** @import { AST } from '#compiler' */
/** @import { ComponentContext } from '../types' */
import { dev } from '../../../../state.js';
import { extract_identifiers } from '../../../../utils/ast.js';
import { extract_identifiers, is_expression_async } from '../../../../utils/ast.js';
import * as b from '#compiler/builders';
import { create_derived } from '../utils.js';
import { get_value } from './shared/declarations.js';
Expand All @@ -17,7 +17,11 @@ export function ConstTag(node, context) {
// TODO we can almost certainly share some code with $derived(...)
if (declaration.id.type === 'Identifier') {
const init = build_expression(context, declaration.init, node.metadata.expression);
let expression = create_derived(context.state, b.thunk(init));
let expression = create_derived(
context.state,
is_expression_async(init) ? b.arrow([], init, true) : b.thunk(init),
is_expression_async(init)
);

if (dev) {
expression = b.call('$.tag', expression, b.literal(declaration.id.name));
Expand Down Expand Up @@ -58,10 +62,11 @@ export function ConstTag(node, context) {
b.block([
b.const(/** @type {Pattern} */ (context.visit(declaration.id, child_state)), init),
b.return(b.object(identifiers.map((node) => b.prop('init', node, node))))
])
]),
is_expression_async(init)
);

let expression = create_derived(context.state, fn);
let expression = create_derived(context.state, fn, is_expression_async(init));

if (dev) {
expression = b.call('$.tag', expression, b.literal('[@const]'));
Expand Down
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