fix(compiler): report invalid directive name error (#4494) (#4495)

packages/compiler-core/src/parse.ts

@@ -775,7 +775,7 @@ function parseAttribute(
   }
   const loc = getSelection(context, start)
 
-  if (!context.inVPre && /^(v-|:|\.|@|#)/.test(name)) {
+  if (!context.inVPre && /^(v-[A-Za-z0-9-]|:|\.|@|#)/.test(name)) {
     const match =
       /(?:^v-([a-z0-9-]+))?(?:(?::|^\.|^@|^#)(\[[^\]]+\]|[^\.]+))?(.+)?$/i.exec(
         name
@@ -888,6 +888,11 @@ function parseAttribute(
     }
   }
 
+  // missing directive name or illegal directive name
+  if (!context.inVPre && startsWith(name, 'v-')) {
+    emitError(context, ErrorCodes.X_MISSING_DIRECTIVE_NAME)
+  }
+
   return {
     type: NodeTypes.ATTRIBUTE,
     name,