react-native: Requiring unknown module "undefined"

I was able to resolve this issue for my project by doing the following…

Given that this issue seems to be caused when there is import {y} from './x' and import {z} from 'myapp/x' in the same file, I was able to track down these files with these steps:

1. Run your app until you get the error message
2. In the stack trace, click on the filename included from your project, under one of the _require items in the stack trace. See screenshot below:

Be sure you have set the REACT_EDITOR variable set so react-native can open the file with an editor

In my file (actions.js), before changes

import {
  getUserEmail
} from 'myapp/user/selectors';

import {
  getUserName
} from './selectors';  //<-- same file as 'myapp/user/selectors'. This is why metro crashes

actions.js after changes

// Change the above to: 
import {
  getUserEmail,
  getUserName
} from 'myapp/user/selectors';

This will also work:

// Or you can change it to: 
import {
  getUserEmail,
  getUserName
} from './selectors';

Now run your app again, and you may get the same error, but it will now point to a different file (assuming you have resolved all imports in the first file). If you get the error in a new file, repeat steps above until all files are cleaned up.

I had to do this 3-4 times before I had found all of the modules that have import {y} from './x' and import {z} from 'myapp/x' in the same file. Hope this helps someone else.

It will work but its up to you

Fix your import, dont use …/…/ for your import, use @.

Same problem

you can use a eslint rule to help on this https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-duplicates.md

Even if that might work, I don’t think this is the solution for the problem… The problem is that the imports are failing and I don’t really understand why…

Reverted to 0.53.3 for now…

It looks like the issue is if you have the same file imported twice by different names in

import string from 'strings'
import commonStrings from 'strings'

This happens also on iOS. Is this related to the metro-bundler? 0.54.1 is facing the same issue and it´s currently blocking from upgrading. Moving to absolute paths would be a huge change right now, so we planned to move the components one after another instead of all 500 files.

Is there maybe any workaround to allow relative paths through the rn-cli.config ?

i also solved with package.json manipulatoin check this out #2051

https://github.com/react-community/react-native-maps/issues/2051#issuecomment-370055156

Seems like this has been fixed in metro with this commit and released in v0.30.2, which react native just bumped its dependency to in master with this commit so hopefully its included in the next release

React native requiring unknown module “492”, if you are sure module is there try restarting metro-bundler.

I got the above error on android OS. I closed the app on the multi-task button and opened the app again from within the emulator and it worked for me.

Are you using react-native-maps ?

If so, react-native-maps may be the problem preventing upgrading to 0.54.0

See: Requiring unknown module “undefined”. #2051

ok fixed my problem, in my case it was An import for a component using relative path, instead of the @ way. replacing that fixed it

Below is what I started seeing, it was working fine, suddenly started seeing below, no clue of what file is causing, tried changing imports

Got exacty this error when I forgot to install and link (pod install)

react-native-vector-icons

Below is what I started seeing, it was working fine, suddenly started seeing below, no clue of what file is causing, tried changing imports

Still a bug on 0.59 as far as I know..

@wildseansy saved me

Hey guys, for me the problem was the following in my index.js (or whatever you call it)

import { AppRegistry } from 'react-native';
import { MyApp } from './app/index';

AppRegistry.registerComponent('my-app', () => MyApp);

MyApp was exported like

export default () => (
    ... some stuff
);

so instead I did the following

const MyApp = () => (
    .. some stuff
);

export { MyApp };

So you may try converting some default exports to named ones.

@rnageli - that is likely a different issue. This one produces Requiring unknown module "undefined", on both Android and iOS consistently. Have tried restarting metro-bundler, re-installing node_modules, clearing caches etc… Doesn’t help.