Version

3.0.5

Reproduction link

https://codesandbox.io/s/divine-fog-7wep8?file=/src/App.vue

Steps to reproduce

Open this page

What is expected?

HelloWorld component rendered.

What is actually happening?

HelloWorld component do not render..

This is because the helloWorld is analyzed as the binding of setup(SETUP_MAYBE_REF) when compileScript analyzes the bindings. It will generate the following code:

export function render(_ctx, _cache, $props, $setup, $data, $options) {
  return (_openBlock(), _createBlock(_Fragment, null, [
    _hoisted_1,
    _createTextVNode(" " + _toDisplayString($setup.helloWorld) + " ", 1 /* TEXT */),
    _createVNode($setup["helloWorld"], { msg: "Hello Vue 3 in CodeSandbox!" })
  ], 64 /* STABLE_FRAGMENT */))
}

Here, $setup["helloWorld"] is problematic.

Workaround: As long as the component name in the template is not the same as the binding, there will be ok.

The source code clearly states that setup components take precedence over user components. Maybe it's not a bug, It's counterintuitive though. @HcySunYang https://github.com/vuejs/vue-next/blob/58c46d77eac05ee72f17aa2669239c4d7c9a3abe/packages/compiler-core/src/transforms/transformElement.ts#L260

This is not about component priority, it is about components/directives and data name conflicts

Maybe it should be resolved in resolveComponent.

Not sure if this is related, but if you have a child component named ChildComponent and setup data named childComponent (so not the same name, but the first letter lowercased) the child also doesn't render. I'm leaving here the console warnings I get, so people can find this bug when searching for a solution:

[Vue warn]: Avoid app logic that relies on enumerating keys on a component instance. The keys will be empty in production mode to avoid performance overhead. 

or sometimes:

[Vue warn]: Invalid vnode type when creating vnode: null.

https://codesandbox.io/s/wonderful-meadow-p8nb6?file=/src/components/ParentComponent.vue

I would say this is not necessary a minor bug, as the label suggests. I've ran into the situation twice already in a short period of time, trying to upgrade an existing vue 2 codebase. And with different console warnings, so had to investigate both times, a lot of time wasted. Imagine a production site having important parts of the page gone missing with no clue as to what is going on.