Merge branch 'main' into fix/select-multiple-dynamic

Uzair-Ahmed-Shah · web-flow · commit fb119fe59dc0 · 2025-12-08T22:33:32.000+05:30
diff --git a/.changeset/two-lizards-poke.md b/.changeset/two-lizards-poke.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: don't crash on `hydratable` serialization failure
diff --git a/package.json b/package.json
@@ -41,7 +41,7 @@
     "prettier-plugin-svelte": "^3.4.0",
     "svelte": "workspace:^",
     "typescript": "^5.5.4",
-    "typescript-eslint": "^8.48.0",
+    "typescript-eslint": "^8.48.1",
     "v8-natives": "^1.2.5",
     "vitest": "^2.1.9"
   }
diff --git a/packages/svelte/src/internal/server/hydratable.js b/packages/svelte/src/internal/server/hydratable.js
@@ -57,32 +57,28 @@ function encode(key, value, unresolved) {
 
 	entry.serialized = devalue.uneval(entry.value, (value, uneval) => {
 		if (is_promise(value)) {
+			// we serialize promises as `"${i}"`, because it's impossible for that string
+			// to occur 'naturally' (since the quote marks would have to be escaped)
+			// this placeholder is returned synchronously from `uneval`, which includes it in the
+			// serialized string. Later (at least one microtask from now), when `p.then` runs, it'll
+			// be replaced.
+			const placeholder = `"${uid++}"`;
 			const p = value
-				.then((v) => `r(${uneval(v)})`)
+				.then((v) => {
+					entry.serialized = entry.serialized.replace(placeholder, `r(${uneval(v)})`);
+				})
 				.catch((devalue_error) =>
 					e.hydratable_serialization_failed(
 						key,
 						serialization_stack(entry.stack, devalue_error?.stack)
 					)
 				);
 
-			// prevent unhandled rejections from crashing the server
-			p.catch(() => {});
-
-			// track which promises are still resolving when render is complete
 			unresolved?.set(p, key);
-			p.finally(() => unresolved?.delete(p));
-
-			// we serialize promises as `"${i}"`, because it's impossible for that string
-			// to occur 'naturally' (since the quote marks would have to be escaped)
-			const placeholder = `"${uid++}"`;
-
-			(entry.promises ??= []).push(
-				p.then((s) => {
-					entry.serialized = entry.serialized.replace(placeholder, s);
-				})
-			);
+			// prevent unhandled rejections from crashing the server, track which promises are still resolving when render is complete
+			p.catch(() => {}).finally(() => unresolved?.delete(p));
 
+			(entry.promises ??= []).push(p);
 			return placeholder;
 		}
 	});
diff --git a/packages/svelte/tests/server-side-rendering/samples/hydratable-unserializable/_config.js b/packages/svelte/tests/server-side-rendering/samples/hydratable-unserializable/_config.js
@@ -0,0 +1,6 @@
+import { test } from '../../test';
+
+export default test({
+	mode: ['async'],
+	error: 'hydratable_serialization_failed'
+});
diff --git a/packages/svelte/tests/server-side-rendering/samples/hydratable-unserializable/main.svelte b/packages/svelte/tests/server-side-rendering/samples/hydratable-unserializable/main.svelte
@@ -0,0 +1,5 @@
+<script lang="ts">
+    import { hydratable } from 'svelte';
+
+    hydratable('key', () => new Promise(() => { throw new Error('nope') }));
+</script>
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +---
 +'svelte': patch
 +---
++
 +fix: don't crash on `hydratable` serialization failure
Original file line number	Diff line number	Diff line change
`@@ -41,7 +41,7 @@`
`41`	`41`	`"prettier-plugin-svelte": "^3.4.0",`
`42`	`42`	`"svelte": "workspace:^",`
`43`	`43`	`"typescript": "^5.5.4",`
`44`		`- "typescript-eslint": "^8.48.0",`
	`44`	`+ "typescript-eslint": "^8.48.1",`
`45`	`45`	`"v8-natives": "^1.2.5",`
`46`	`46`	`"vitest": "^2.1.9"`
`47`	`47`	`}`