Expected VDOM node to be a DOM node but got undefined - piocstyle/preact x beta 3 about enzyme-adapter-preact-pure HOT 5 CLOSED

After some debugging, it looks like picostyle is subtly broken with Preact 10.

When the wrapper component is rendered, it is called with two arguments: props and context, where context defaults to an empty object ({}). The place where Preact calls the picostyle component's render function is here: https://github.com/preactjs/preact/blob/984f18dc20cc7a2ec3cd30f29c25aac0c53dbca0/src/diff/index.js#L311

Picostyle however expects the render function to be called with the second argument being the children of the component, not the context. This should be an element, string or array. See https://github.com/morishitter/picostyle/blob/9f4053f806adbedbd7ee916e42f8153fbaccd948/src/index.js#L57

The result is that an invalid vnode gets generated which later trips up the Enzyme adapter, and probably breaks other things as well.

The error can be reproduced without Picostyle using:

import { h } from "preact";
import { configure, mount } from "enzyme";
import { Adapter } from "enzyme-adapter-preact-pure";

function App() {
  return h('div', {}, {} /* Not a valid `children` argument */);
}

configure({ adapter: new Adapter() });

mount(<App />);

The preact/debug package could potentially catch this error when h is called and warn the developer about it. In the meantime, since the problem is not an issue with the adapter itself, I'm going to close this issue. If you could report it upstream to the Picostyle author, that would be appreciated.

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Hello @samueljseay, I created a quick test on CodeSandbox using Preact 10, picostyle and Enzyme but was unable to reproduce the issue.

Can you please create a minimal project that reproduces the problem, either as a Code Sandbox, GitHub repo or Gist and post the link here.

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Thanks all! I will raise this on picostyle!

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@robertknight I was able to reproduce it with your example, just mount the picostyle node directly: https://codesandbox.io/s/preact-picostyle-enzyme-ctifh

from enzyme-adapter-preact-pure.

Yeah that function signature in picostyle is wrong. The second argument has never been children, even for other libraries as far as I can tell.

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