fix: allow rest params to be empty in resolvePath (#10146)

fixes #10140

Author: gtm-nayan

.changeset/metal-toes-talk.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: allow rest params to be empty in resolvePath

packages/kit/src/exports/index.js

@@ -104,7 +104,7 @@ export function fail(status, data) {
 	return new ActionFailure(status, data);
 }
 
-const basic_param_pattern = /\[(\[)?(?:\.\.\.)?(\w+?)(?:=(\w+))?\]\]?/g;
+const basic_param_pattern = /\[(\[)?(\.\.\.)?(\w+?)(?:=(\w+))?\]\]?/g;
 
 /**
  * Populate a route ID with params to resolve a pathname.
@@ -128,12 +128,13 @@ export function resolvePath(id, params) {
 		'/' +
 		segments
 			.map((segment) =>
-				segment.replace(basic_param_pattern, (_, optional, name) => {
+				segment.replace(basic_param_pattern, (_, optional, rest, name) => {
 					const param_value = params[name];
 
 					// This is nested so TS correctly narrows the type
 					if (!param_value) {
 						if (optional) return '';
+						if (rest && param_value !== undefined) return '';
 						throw new Error(`Missing parameter '${name}' in route ${id}`);
 					}
 

packages/kit/src/exports/index.spec.js

@@ -22,6 +22,11 @@ const from_params_tests = [
 		params: { one: 'one', two: '2', three: '3' },
 		expected: '/blog/one/2-and-3'
 	},
+	{
+		route: '/blog/[...one]',
+		params: { one: '' },
+		expected: '/blog'
+	},
 	{
 		route: '/blog/[one]/[...two]-not-three',
 		params: { one: 'one', two: 'two/2' },