fix: make it work when a default lang was specified

ref: vitejs/vite-plugin-vue@ff68ed3

Author: sxzz

src/core/main.ts

@@ -268,7 +268,7 @@ async function genTemplateCode(
   // If the template is not using pre-processor AND is not using external src,
   // compile and inline it directly in the main module. When served in vite this
   // saves an extra request per SFC which can improve load performance.
-  if (!template.lang && !template.src) {
+  if ((!template.lang || template.lang === 'html') && !template.src) {
     return transformTemplateInMain(
       template.content,
       descriptor,

src/core/script.ts

@@ -113,7 +113,7 @@ export function canInlineMain(
     return false
   }
   const lang = descriptor.script?.lang || descriptor.scriptSetup?.lang
-  if (!lang) {
+  if (!lang || lang === 'js') {
     return true
   }
   if (

src/core/template.ts

@@ -175,7 +175,7 @@ export function resolveTemplateCompilerOptions(
     ssr,
     ssrCssVars: cssVars,
     transformAssetUrls,
-    preprocessLang: block.lang,
+    preprocessLang: block.lang === 'html' ? undefined : block.lang,
     preprocessOptions,
     compilerOptions: {
       ...options.template?.compilerOptions,