Material-ui: 'SKIP_PREFLIGHT_CHECK' is not recognized as an internal or external command, operable program or batch file.

[PhazonJim]

• [x ] The issue is present in the latest release.
• [ x] I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

Using the create-react-app example:
1) Download the example or clone the repo
2) npm install
3) npm start

npm start throws the following error in Windows 10:

[email protected] start C:\Users\janit\Desktop\create-react-app
SKIP_PREFLIGHT_CHECK=true react-scripts start

'SKIP_PREFLIGHT_CHECK' is not recognized as an internal or external command,
operable program or batch file.

Expected Behavior 🤔

npm starts the react app

Steps to Reproduce 🕹

Steps:
(On Windows 10)
Using the create-react-app example:

1. Download the example or clone the repo
2. npm install
3. npm start

Context 🔦

Your Environment 🌎

| Tech | Version |
| ----------- | ------- |
| Material-UI | v4.4.3 |
| React | v16.9.0 |
| Browser | Chrome |
| TypeScript | No |
| etc. | Windows 10 |

[support[bot]]

👋 Thanks for using Material-UI!

We use GitHub issues exclusively as a bug and feature requests tracker, however,
this issue appears to be a support request.

For support, please check out https://material-ui.com/getting-started/support/. Thanks!

If you have a question on StackOverflow, you are welcome to link to it here, it might help others.
If your issue is subsequently confirmed as a bug, and the report follows the issue template, it can be reopened.

[PhazonJim]

Hey @eps1lon this is not a support request, this is a legitimate bug/issue. Package.json changes made 4 months ago here: https://github.com/mui-org/material-ui/blame/f67c2014164267ca9f0603e513deba46f24c47fc/examples/create-react-app/package.json#L6

Causes this to completely not work on Windows machines.

[eps1lon]

Sorry I missed the part that this was taken from our example. This is indeed an issue (not just for windows but any shell that doesn't support this syntax).

Should use cross-env instead.

[johnhe66]

Tried cross-env and not working. To clarify, in package.json, instead of having,
"start": "SKIP_PREFLIGHT_CHECK=true react-scripts start",
It should be changed to,
"start": "cross-env=true react-scripts start",

Please advise.

[eps1lon]

"start": "cross-env SKIP_PREFLIGHT_CHECK=true react-scripts start"

[PhazonJim]

"start": "cross-env SKIP_PREFLIGHT_CHECK=true react-scripts start"

^ Yes that is the exact fix I ended up using last night. You will need to install cross-env as a dev-dependency.

[joshwooding]

Could we use the .env support in create-react-app to achieve this without the extra dependency?

[oliviertassinari]

Should this env variable be used in the first place?

[PhazonJim]

I'm not sure what the rationale was in adding it so recently.

[oliviertassinari]

It was left by mistake in #15219, I think that we should remove it:

diff --git a/examples/create-react-app/package.json b/examples/create-react-app/package.json
index 0b9bffe6a..5db2f0fc6 100644
--- a/examples/create-react-app/package.json
+++ b/examples/create-react-app/package.json
@@ -3,7 +3,7 @@
   "version": "4.0.0",
   "private": true,
   "scripts": {
-    "start": "SKIP_PREFLIGHT_CHECK=true react-scripts start",
+    "start": "react-scripts start",
     "build": "react-scripts build",
     "test": "react-scripts test",
     "eject": "react-scripts eject"