fix(runtime-vapor): properly mount component only with template in production mode (#12727)

Co-authored-by: Evan You <evan@vuejs.org>

packages/runtime-vapor/__tests__/component.spec.ts

@@ -282,6 +282,24 @@ describe('component', () => {
     expect(i.scope.effects.length).toBe(0)
   })
 
+  test('should mount component only with template in production mode', () => {
+    __DEV__ = false
+    const { component: Child } = define({
+      render() {
+        return template('<div> HI </div>', true)()
+      },
+    })
+
+    const { host } = define({
+      setup() {
+        return createComponent(Child, null, null, true)
+      },
+    }).render()
+
+    expect(host.innerHTML).toBe('<div> HI </div>')
+    __DEV__ = true
+  })
+
   it('warn if functional vapor component not return a block', () => {
     define(() => {
       return () => {}

packages/runtime-vapor/src/component.ts

@@ -212,8 +212,18 @@ export function createComponent(
       }
     }
   } else {
-    // in prod result can only be block
-    instance.block = setupResult as Block
+    // component has a render function but no setup function
+    // (typically components with only a template and no state)
+    if (!setupFn && component.render) {
+      instance.block = callWithErrorHandling(
+        component.render,
+        instance,
+        ErrorCodes.RENDER_FUNCTION,
+      )
+    } else {
+      // in prod result can only be block
+      instance.block = setupResult as Block
+    }
   }
 
   // single root, inherit attrs