fix: escape backslahes in string literals

Fix #2640

Author: posva

packages/router/src/unplugin/codegen/generateRouteRecords.spec.ts

@@ -365,6 +365,18 @@ describe('generateRouteRecord', () => {
     })
   })
 
+  it('preserves backslashes in path overrides', () => {
+    const tree = new PrefixTree(DEFAULT_OPTIONS)
+    tree.insert('test/[id]', 'test/[id].vue')
+    const node = tree.insert('test/[id]/index', 'test/[id]/index.vue')
+    node.setCustomRouteBlock('test/[id]/index', {
+      path: '/:id(\\d+)',
+    })
+
+    const result = generateRouteRecordSimple(tree)
+    expect(result).toContain("path: '/:id(\\\\d+)'")
+  })
+
   describe('raw paths insertions', () => {
     it('works with raw paths', () => {
       const tree = new PrefixTree(DEFAULT_OPTIONS)

packages/router/src/unplugin/utils/index.ts

@@ -55,5 +55,5 @@ export function formatMultilineUnion(items: string[], spaces: number): string {
  * toStringLiteral("it's fine") // returns "'it\'s fine'"
  */
 export function toStringLiteral(str: string): string {
-  return `'${str.replace(/'/g, "\\'")}'`
+  return `'${str.replace(/\\/g, '\\\\').replace(/'/g, "\\'")}'`
 }