fix: avoid scan failures in .svelte and .astro files (#5193)

Co-authored-by: Bjorn Lu <34116392+bluwy@users.noreply.github.com>

Author: benmccann

packages/vite/src/node/optimizer/scan.ts

@@ -272,11 +272,15 @@ function esbuildScanPlugin(
             }
           }
 
-          if (!code.includes(`export default`)) {
-            js += `\nexport default {}`
+          // This will trigger incorrectly if `export default` is contained
+          // anywhere in a string. Svelte and Astro files can't have
+          // `export default` as code so we know if it's encountered it's a
+          // false positive (e.g. contained in a string)
+          if (!path.endsWith('.vue') || !js.includes('export default')) {
+            js += '\nexport default {}'
           }
 
-          if (code.includes('import.meta.glob')) {
+          if (js.includes('import.meta.glob')) {
             return {
               // transformGlob already transforms to js
               loader: 'js',