fix: use acceptExports to support partial hmr (#11453)

* fix: use acceptExports to support partial hmr

* fix: add condition to only use acceptExports when it is available

* fix: update test snapshot

* fix: format

Author: dominikg

.changeset/slimy-onions-approve.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: use import.meta.hot.acceptExports when available to support partial hmr in vite

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

@@ -429,23 +429,23 @@ export function client_component(source, analysis, options) {
 	);
 
 	if (options.hmr) {
+		const accept_fn = b.arrow(
+			[b.id('module')],
+			b.block([b.stmt(b.call('$.set', b.id('s'), b.member(b.id('module'), b.id('default'))))])
+		);
 		body.push(
 			component,
 			b.if(
 				b.id('import.meta.hot'),
 				b.block([
 					b.const(b.id('s'), b.call('$.source', b.id(analysis.name))),
 					b.stmt(b.assignment('=', b.id(analysis.name), b.call('$.hmr', b.id('s')))),
-					b.stmt(
-						b.call(
-							'import.meta.hot.accept',
-							b.arrow(
-								[b.id('module')],
-								b.block([
-									b.stmt(b.call('$.set', b.id('s'), b.member(b.id('module'), b.id('default'))))
-								])
-							)
-						)
+					b.if(
+						b.id('import.meta.hot.acceptExports'),
+						b.stmt(
+							b.call('import.meta.hot.acceptExports', b.array([b.literal('default')]), accept_fn)
+						),
+						b.stmt(b.call('import.meta.hot.accept', accept_fn))
 					)
 				])
 			),

packages/svelte/tests/snapshot/samples/hmr/_expected/client/index.svelte.js

@@ -14,9 +14,11 @@ if (import.meta.hot) {
 
 	Hmr = $.hmr(s);
 
-	import.meta.hot.accept((module) => {
+	if (import.meta.hot.acceptExports) import.meta.hot.acceptExports(["default"], (module) => {
+		$.set(s, module.default);
+	}); else import.meta.hot.accept((module) => {
 		$.set(s, module.default);
 	});
 }
 
-export default Hmr;
+export default Hmr;