Support setupProxy.mjs

Is your proposal related to a problem?

Now as Node.JS 13.2 un-prefixed ES 6 Modules, I’d like to use ES 6 imports in my setupProxy.mjs, but CRA forces me to use setupProxy.js.

Describe the solution you’d like

Next to setupProxy.js, allow to use setupProxy.mjs (or setupProxy.cjs).

See also https://nodejs.org/api/esm.html#esm_enabling.

[kenlyon]

I have a workaround. It’s pretty gross, but it got me unstuck today.

My app is using ESM as the default format. My /package.json has "type": "module".

When I made the change, the react-app-rewired build complained about /src/setupProxy.js being ESM so I changed it to .cjs and thought I was done. Only today (weeks later) did I notice that /src/setupProxy.cjs is ignored.

Here’s the fix for defining your own custom setupProxy logic in an ESM world:

1. Create a folder called /src/setupProxy.js.
2. Move your old setupProxy content into a new file called /src/setupProxy.js/index.js. The content of this file must be in CommonJS format.
3. Create a file called /src/setupProxy.js/package.json that contains the text { "type": "commonjs" }. This ensures the neighbouring file is loaded as CommonJS, so it will work when it’s “require’d” in.

So, to recap - your structure should now be:

• src
  • setupProxy.js (a directory!)
    • index.js
    • package.json

It’s not pretty, but it works!

Thanks to @eric-parsons for the idea of a directory with the .js extension. That was the key!

[RThevenoux]

@kenlyon Thank you very much ! I don’t know if there is a fix for this problem, but your solution save my day !