fix: detect route conflicts in nested groups with optional params

.changeset/fix-route-conflict-nested-groups.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: detect route conflicts in nested groups with optional params

packages/kit/src/core/sync/create_manifest_data/index.js

@@ -561,7 +561,7 @@ function prevent_conflicts(routes) {
 			// remove leading/trailing/duplicated slashes caused by prior
 			// manipulation of optional parameters and (groups)
 			const key = permutation
-				.replace(/\/{2,}/, '/')
+				.replace(/\/{2,}/g, '/')
 				.replace(/^\//, '')
 				.replace(/\/$/, '');
 

packages/kit/src/core/sync/create_manifest_data/index.spec.js

@@ -790,6 +790,13 @@ test('prevents route conflicts between groups', () => {
 	);
 });
 
+test('prevents route conflicts between nested groups with optional params', () => {
+	assert.throws(
+		() => create('samples/conflicting-nested-groups'),
+		/routes conflict with each other/
+	);
+});
+
 test('errors with multiple layouts on same directory', () => {
 	assert.throws(
 		() => create('samples/multiple-layouts'),