Using <React.Fragment> prints warning with enzyme's mount with IE11

[sylvain-hamel]

I have a component that returns a <React.Fragment> object. When I mount the component using enzyme, in Internet Explorer 11, then React prints out this warning:

Warning: React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: object.

Followed by this warning:

Warning: Each child in an array or iterator should have a unique "key" prop. See https://fb.me/react-warning-keys for more information

About the 2nd warning, I'm pretty sure it's confusing the Fragment "array" with a common JSX array and it's trying to validate that each of the Fragment "element" has a key.

More info:

• The same test runs without any warning on Chrome, Edge and Firefox.
• This does not happen when I load the application on screen in Internet Explorer 11. It only happens in my unit tests; this is why I think it's related to enzyme.

Current behavior

Some warnings are printed

Expected behavior

No warnings should be printed

Your environment

Windows, Internet Explorer, Karma, Jasmine

API

• shallow
• mount
• render

Version

library	version
Enzyme	3.2.0
React	16.2.0

Adapter

• enzyme-adapter-react-16
• enzyme-adapter-react-15
• enzyme-adapter-react-15.4
• enzyme-adapter-react-14
• enzyme-adapter-react-13
• enzyme-adapter-react-helper
• others ( )

[ljharb]

See #1213; fragments aren't properly supported yet.

[sylvain-hamel]

I knew about that issue, but because my problem only occurs on IE11 I thought it could be a different thing. I'll wait for #1213 then. Thanks.

[sanshuiwang]

This problem appears in the development environment, the production environment did not.
so we can to ignore, do not worry.

[ljharb]

@sanshuiwang since enzyme is a testing framework, and tests are only run in a development environment, it's definitely not something that can be ignored.

[ljharb]

@sylvain-hamel can you still reproduce this with latest enzyme? if not, please close; if so, can you provide the component code that's erroring?

[ljharb]

I'm going to close this, pending repro info.