Support ES5 (again)

[jjmac]

• dom-testing-libraryversion: 3.16.6
• react-testing-libraryversion: 5.8.0
• react version: 16.8.1
• node version: 10.15.1
• npm (or yarn) version: 6.4.1
• @storybook/reactversion: 4.1.11
• storybook-addon-specificationsversion: 2.1.2

What you did / Problem description:

Trying to run tests in IE11 results in a syntax error because the dist targets ES6.

The break occurs at the first arrow function in dom-testing-library/events.js line 310:

Object.keys(eventMap).forEach(key => { ...

Test are being run in storybook using storybook-addon-specifications. Works great in Chrome but breaks in IE11 due to ES6 syntax in distribution

Suggested solution:

Target ES5 or provide an ES5 build?
This was fixed previously in #160 but that seems to be due to an external dependency.

The project is setup using create-react-app and is using craco for some overrides - is there a way to re-target specific dependencies to ES5?

[jjmac]

Ugh. So I think I found the solution - I need to import the specific UMD file in react-testing-library to pick-up the ES5 distro:

import {
    cleanup,
    render
} from "react-testing-library/dist/react-testing-library.umd";

[alexkrolick]

Seems somewhat related to #216 - is the build step targeting node: 'current' or something instead of a browser target? Seems like we should be able to:

• map each dist file to a specific target
• guarantee at least the UMD bundle is IE11-compatible
• document how to consume each bundle

[jjmac]

the build is targeting ES5, it's just that node modules aren't transpiled. Importing from "react-testing-library" packages ES6 code which is fine in the node cli and modern browsers but throws in IE11.

The UMD bundle is IE11 compatible, I think maybe this is just a documentation issue. It doesn't seem that the use case for running tests in IE11 is a common one.

[kentcdodds]

It doesn't seem that the use case for running tests in IE11 is a common one.

Yes, this is true.

I think we're going to go with requiring people to use the UMD if they need old browser support. Maybe we could add a note to the docs?

What do you all think?