Debugging in Chrome and FireFox not evaluating "let" and "const" vars

Is this a bug report?

Yes, though not entirely sure it’s CRA related, may be babel or webpack.

Can you also reproduce the problem with npm 4.x?

I don’t think it’s relevant, but will try if requested.

Which terms did you search for in User Guide?

DevTools, Chrome, ES6, Source Maps, lots of other googling beyond

Environment

1. node -v: 8.7.0
2. npm -v: 5.4.2
3. yarn --version (if you use Yarn):
4. npm ls react-scripts (if you haven’t ejected): 1.0.14

Then, specify:

1. Operating system: Windows 10
2. Browser and version (if relevant): Chrome Chrome 62.0.3202.94, FireFox 57.0.1

Steps to Reproduce

As far as I can tell, it’s a simple as:

1. Write a module that uses ES6 const and let keys words inside a switch statement. For me, it’s in a redux reducer
2. npm run start
3. Debug the module, see something similar to below:

Expected Behavior

Variables to evaluate properly

Actual Behavior

state is defined, newState should be defined, but is not. I’m wondering if this is because I use similar naming in each switch case block.

I’ve also removed all Flow typing from the file, same result. I’ve also tried several devtool options for Webpack with no changes.

Reproducible Demo

https://github.com/facebookincubator/create-react-app/issues/3597#issuecomment-356338424

[TheTFo]

Sorry, Dan. I got caught up with the holidays, and this fell off.

I can’t share my code, but I’ll try to put together a reproduction tomorrow.

On Mon, Jan 8, 2018, 7:08 PM Dan Abramov [e-mail] wrote:

This will need some investigation. I don’t know if there’s a way to fix it with Babel/Webpack but it’s worth looking into. Unfortunately I won’t have time to do it myself.

cc @samccone https://github.com/samccone @paulirish https://github.com/paulirish Can somebody on your side help us figure out why this broke? I think it used to work although I might be wrong.

@TheTFo https://github.com/thetfo @d07RiV https://github.com/d07riv Please prepare a reproducing example, it’s very hard to help you if you didn’t create one. This issue could’ve progressed if you spent a few minutes sharing it.

— You are receiving this because you were mentioned.

Reply to this email directly, view it on GitHub https://github.com/facebookincubator/create-react-app/issues/3597#issuecomment-356137229, or mute the thread https://github.com/notifications/unsubscribe-auth/AAgWoF9n4zE7tmfjZKGX7Vci0QzHNOK9ks5tIq4AgaJpZM4RBfiE .

[TheTFo]

I tried with various devtool settings, and nothing seemed to fix it. Also noticed in FireFox.