ES6 module build includes references to `process.env.NODE_ENV`

Describe the bug The ES6 module build includes references to process.env.NODE_ENV, which breaks browser usages – browsers now support ES6 modules. This is hidden by react-scripts in Codesandbox.io because it provides a definition for process.env.NODE_ENV.

To Reproduce Steps to reproduce the behavior:

1. Use Rollup to create an ES6 module build that runs in the browser.
2. Pass register to the ref prop as done in just about every example.
3. Run the code in the browser.
4. Open the JS console and note the “process is not defined” error.

Codesandbox link (Required) I flipped a table trying to get Codesandbox to not use create-react-app. I hope you don’t mind if I just created a dedicated repo with reproduction instructions in the README:

https://github.com/spaceaardvark/react-hook-form-bug1

Expected behavior The browser build should not encounter or use process.env.NODE_ENV.

Desktop (please complete the following information):

• OS: Ubuntu 20
• Chrome
• v86.0.4240.198

Additional context From conversation in #1441 after it was closed.

[jorisre]

👋🏻

@spaceaardvark Thanks for reporting. Your use case is really interesting ! Thanks for the reproduction. I think you mean modern module (es6) . At this time, RHF’s ES6 module is not a modern module, that’s why it contains process.env.*.

@bluebill1049 Yes, this can be solved by using microbundle which provide modern bundle. I started to switch from custom rollup config to microbundle this morning 😉

[jorisre]

I mean I don’t know where I have to add the modern bundle in the exports field of the package.json: https://nodejs.org/api/packages.html#packages_conditional_exports

We use exports too for resovlers but not for modern https://github.com/react-hook-form/resolvers/pull/108/files#diff-7ae45ad102eab3b6d7e7896acd08c427a9b25b346470d7bc6507b6481575d519R11

Is it more clear ?