React-Hot-Loader is not supported in this environment.

[wulucxy]

If you are reporting a bug or having an issue setting up React Hot Loader, please fill in below. For feature requests, feel free to remove this template entirely.

Description

when run npm start，cli will console out：

React-Hot-Loader is not supported in this environment.

Expected behavior

when run npm script，why did this happen?

Actual behavior

not waring msg

Environment

React Hot Loader version: 4.7.1

Run these commands in the project folder and fill in their results:

1. node -v: 8.10.0
2. npm -v: 5.6.0

[borisding]

Hi!

I'm having same message after applying https://github.com/gaearon/react-hot-loader#webpack-plugin for my SSR project.

[theKashey]

  var evalAllowed = false;
  try {
    eval('evalAllowed = true');
  } catch (e) {
    // eval not allowed due to CSP
  }

  // RHL needs setPrototypeOf to operate Component inheritance, and eval to patch methods
  var jsFeaturesPresent = typeof window !== 'undefined' && !!Object.setPrototypeOf;

  if (!jsFeaturesPresent || !evalAllowed) {
    // we are not in prod mode, but RHL could not be activated
    console.warn('React-Hot-Loader is not supported in this environment.');
    ....
  }

So, which variable - jsFeaturesPresent or evalAllowed is falsy?

[borisding]

  var evalAllowed = false;
  try {
    eval('evalAllowed = true');
  } catch (e) {
    // eval not allowed due to CSP
  }

  // RHL needs setPrototypeOf to operate Component inheritance, and eval to patch methods
  var jsFeaturesPresent = typeof window !== 'undefined' && !!Object.setPrototypeOf;

  if (!jsFeaturesPresent || !evalAllowed) {
    // we are not in prod mode, but RHL could not be activated
    console.warn('React-Hot-Loader is not supported in this environment.');
    ....
  }

So, which variable - jsFeaturesPresent or evalAllowed is falsy?

It's showing

jsFeaturesPresent: false
evalAllowed: true

[taikn]

Same here jsFeaturesPresent: false, typeof window is undefined

[theKashey]

@borisding - so there is no window in SSR, and there is no RHL on SSR side - it relies on module update API, which does not exist on the server side.

I would say - the right way to mitigate the problem - suppress this message on SSR.