From b06e4356848ab3375797e634fd6c6114a9643252 Mon Sep 17 00:00:00 2001
From: Emil Tholin <emtholin@gmail.com>
Date: Tue, 10 Jan 2023 09:39:50 +0100
Subject: [PATCH] [fix] Spread component props immutably during SSR (#8176)

By passing an empty object literal as first argument to Object.assign we can avoid having objects spread as props on a component being mutated during SSR.

Fixes #8171
---
 .../render_ssr/handlers/InlineComponent.ts        |  2 +-
 .../spread-component-immutable/Widget.svelte      |  0
 .../samples/spread-component-immutable/_config.js | 15 +++++++++++++++
 .../spread-component-immutable/main.svelte        |  7 +++++++
 4 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 test/runtime/samples/spread-component-immutable/Widget.svelte
 create mode 100644 test/runtime/samples/spread-component-immutable/_config.js
 create mode 100644 test/runtime/samples/spread-component-immutable/main.svelte

diff --git a/src/compiler/compile/render_ssr/handlers/InlineComponent.ts b/src/compiler/compile/render_ssr/handlers/InlineComponent.ts
index 8287b46268..73d31940e2 100644
--- a/src/compiler/compile/render_ssr/handlers/InlineComponent.ts
+++ b/src/compiler/compile/render_ssr/handlers/InlineComponent.ts
@@ -36,7 +36,7 @@ export default function(node: InlineComponent, renderer: Renderer, options: Rend
 	let props;
 
 	if (uses_spread) {
-		props = x`@_Object.assign(${
+		props = x`@_Object.assign({}, ${
 			node.attributes
 				.map(attribute => {
 					if (attribute.is_spread) {
diff --git a/test/runtime/samples/spread-component-immutable/Widget.svelte b/test/runtime/samples/spread-component-immutable/Widget.svelte
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/test/runtime/samples/spread-component-immutable/_config.js b/test/runtime/samples/spread-component-immutable/_config.js
new file mode 100644
index 0000000000..634fac24c1
--- /dev/null
+++ b/test/runtime/samples/spread-component-immutable/_config.js
@@ -0,0 +1,15 @@
+const obj = {
+	x: 1,
+	y: 2,
+	z: 3
+};
+
+export default {
+	props: {
+		obj
+	},
+
+	test({ assert }) {
+		assert.deepEqual(obj, { x: 1, y: 2, z: 3 });
+	}
+};
diff --git a/test/runtime/samples/spread-component-immutable/main.svelte b/test/runtime/samples/spread-component-immutable/main.svelte
new file mode 100644
index 0000000000..44e0954856
--- /dev/null
+++ b/test/runtime/samples/spread-component-immutable/main.svelte
@@ -0,0 +1,7 @@
+<script>
+	import Widget from './Widget.svelte';
+
+	export let obj;
+</script>
+
+<Widget {...obj} x={2} />