fix(plugin-vue): special handling for class default export in sfc

close #1476

Author: yyx990803

packages/plugin-vue/src/main.ts

@@ -207,6 +207,8 @@ async function genTemplateCode(
   }
 }
 
+const exportDefaultClassRE = /export\s+default\s+class\s+([\w$]+)/
+
 async function genScriptCode(
   descriptor: SFCDescriptor,
   options: ResolvedOptions,
@@ -226,7 +228,14 @@ async function genScriptCode(
       (!script.lang || (script.lang === 'ts' && options.devServer)) &&
       !script.src
     ) {
-      scriptCode = rewriteDefault(script.content, `_sfc_main`)
+      const classMatch = script.content.match(exportDefaultClassRE)
+      if (classMatch) {
+        scriptCode =
+          script.content.replace(exportDefaultClassRE, `class $1`) +
+          `\nconst _sfc_main = ${classMatch[1]}`
+      } else {
+        scriptCode = rewriteDefault(script.content, `_sfc_main`)
+      }
       map = script.map
       if (script.lang === 'ts') {
         const result = await options.devServer!.transformWithEsbuild(