ArrayField + SingleFieldList: if embedded data doesn't have an id, rows won't have a key and will cause a React warning

[smeng9]

What you were expecting:

Using an ArrayField + SingleFieldListfor embedded data that doesn't have an id prop should work without console errors

What happened instead:

I get this error in the console: Warning: Each child in a list should have a unique "key" prop.

Steps to reproduce:

1. Goto https://hs0dpi.sse.codesandbox.io/#/posts/12/show
2. Open console to see the warning

Related code:

https://codesandbox.io/s/stoic-glade-hs0dpi?file=/src/posts/PostShow.tsx:1269-1446

Other information:

This is where the key is set based on the id, which doesn't exist in this case:

https://github.com/marmelab/react-admin/blob/master/packages/ra-ui-materialui/src/list/SingleFieldList.tsx#L102

Environment

• React-admin version: 4.0.2
• Last version that did not exhibit the issue (if applicable):
• React version: 18.1.0
• Browser:
• Stack trace (in case of a JS error):

[smeng9]

Duplicate of #7541

The fix should be similar to #7548 and just one or two lines