Release v3.9.5 broke layout prop

What you were expecting: On v3.9.4 I used layout prop and passed in it my custom layout component.

What happened instead: After upgrading to v3.9.5 I started getting the following error and the app stoped working:

Error: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports.

Steps to reproduce: I was able to identify the problem and it turned out to be with a custom layout component.

Related code: https://codesandbox.io/s/cranky-sanderson-2l2tm?fontsize=14&hidenavigation=1&theme=dark&file=/src/App.tsx

If you comment out the layout component, everything works. If you add it again, the app break with the error that I specified above.

Environment

• React-admin version: v3.9.5
• Last version that did not exhibit the issue (if applicable): v3.9.4
• React version: 17.0.1
• Browser: Google Chrom
• Stack trace (in case of a JS error):

[Luwangel]

It’s because we use internally createElement for the appBar, and cloneElement for the userMenu. But it’s difficult to change it at the moment because it’ll introduce a breaking change. We need to think about it for the v4.

[mariaefi29]

Could you please tell me why in AppBar for example you don’t need to pass as a react element?

this works: return <Layout {...props} appBar={CustomAppBar} />;