From 710c3a6594117509903e974e347d02eee3cb4549 Mon Sep 17 00:00:00 2001
From: paoloricciuti <ricciutipaolo@gmail.com>
Date: Sat, 19 Oct 2024 23:17:03 +0200
Subject: [PATCH] fix: don't blank css on migration error

---
 .changeset/healthy-bees-wave.md                      |  5 +++++
 packages/svelte/src/compiler/migrate/index.js        |  3 ++-
 .../samples/not-blank-css-if-error/input.svelte      | 11 +++++++++++
 .../samples/not-blank-css-if-error/output.svelte     | 12 ++++++++++++
 4 files changed, 30 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/healthy-bees-wave.md
 create mode 100644 packages/svelte/tests/migrate/samples/not-blank-css-if-error/input.svelte
 create mode 100644 packages/svelte/tests/migrate/samples/not-blank-css-if-error/output.svelte

diff --git a/.changeset/healthy-bees-wave.md b/.changeset/healthy-bees-wave.md
new file mode 100644
index 0000000000..6a31a94e3a
--- /dev/null
+++ b/.changeset/healthy-bees-wave.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: don't blank css on migration error
diff --git a/packages/svelte/src/compiler/migrate/index.js b/packages/svelte/src/compiler/migrate/index.js
index b0867766e3..f2b6977ea1 100644
--- a/packages/svelte/src/compiler/migrate/index.js
+++ b/packages/svelte/src/compiler/migrate/index.js
@@ -34,6 +34,7 @@ let has_migration_task = false;
  * @returns {{ code: string; }}
  */
 export function migrate(source, { filename } = {}) {
+	let og_source = source;
 	try {
 		has_migration_task = false;
 		// Blank CSS, could contain SCSS or similar that needs a preprocessor.
@@ -303,7 +304,7 @@ export function migrate(source, { filename } = {}) {
 		console.error('Error while migrating Svelte code', e);
 		has_migration_task = true;
 		return {
-			code: `<!-- @migration-task Error while migrating Svelte code: ${/** @type {any} */ (e).message} -->\n${source}`
+			code: `<!-- @migration-task Error while migrating Svelte code: ${/** @type {any} */ (e).message} -->\n${og_source}`
 		};
 	} finally {
 		if (has_migration_task) {
diff --git a/packages/svelte/tests/migrate/samples/not-blank-css-if-error/input.svelte b/packages/svelte/tests/migrate/samples/not-blank-css-if-error/input.svelte
new file mode 100644
index 0000000000..c31b74df34
--- /dev/null
+++ b/packages/svelte/tests/migrate/samples/not-blank-css-if-error/input.svelte
@@ -0,0 +1,11 @@
+<script>
+	export let error = true;
+</script>
+
+{$$props}
+
+<style lang="postcss">
+	div{
+		color: red;
+	}
+</style>
\ No newline at end of file
diff --git a/packages/svelte/tests/migrate/samples/not-blank-css-if-error/output.svelte b/packages/svelte/tests/migrate/samples/not-blank-css-if-error/output.svelte
new file mode 100644
index 0000000000..a62a6d4d90
--- /dev/null
+++ b/packages/svelte/tests/migrate/samples/not-blank-css-if-error/output.svelte
@@ -0,0 +1,12 @@
+<!-- @migration-task Error while migrating Svelte code: $$props is used together with named props in a way that cannot be automatically migrated. -->
+<script>
+	export let error = true;
+</script>
+
+{$$props}
+
+<style lang="postcss">
+	div{
+		color: red;
+	}
+</style>
\ No newline at end of file