Requiring unknown module "undefined"

[jkbreunig]

Error after upgrading 0.54.0 from 0.53.3.

Requiring unknown module "undefined".If you are sure the module is there, try restarting Metro Bundler. You may also want to run yarn, or npm install (depending on your environment).
handleException @ ExceptionsManager.js:65
handleError @ InitializeCore.js:115
reportFatalError @ error-guard.js:44
guardedLoadModule @ require.js:141
_require @ require.js:130
executeApplicationScript @ debuggerWorker.js:40
(anonymous) @ debuggerWorker.js:65
ExceptionsManager.js:65 Module AppRegistry is not a registered callable module (calling runApplication)

Environment

Environment:
OS: macOS High Sierra 10.13.3
Node: 8.9.4
Yarn: 1.5.1
npm: 5.6.0
Watchman: 4.9.0
Xcode: Xcode 9.2 Build version 9C40b
Android Studio: 3.0 AI-171.4443003

Packages: (wanted => installed)
react: ^16.3.0-alpha.1 => 16.3.0-alpha.1
react-native: 0.54.0 => 0.54.0

Expected Behavior

App should launch

Actual Behavior

UnknownModuleError

Steps to Reproduce

react-native run-android

[Jeepeng]

Same problem

[almostintuitive]

Same here! This is a blocking issue for us.

[mobdim]

Same problem. A few days can't solve.

[HumanUndead]

same problem, stuck too

[Maydar]

same issue

[hugoskwirrel]

react-native-maps/react-native-maps#2051 (comment)

[hramos]

Can you clarify - this happens on a brand new project?

[HumanUndead]

this happens after upgrading from 0.53.3 to 0.54 not on the whole project but some screens

[HumanUndead]

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

[cipriancaba]

@HumanUndead Do you have an example of what your problem is? I have a simple class export that is failing with undefined

export class TouchableOpacityWebSafe extends Component { ... }

and importing with

import { TouchableOpacityWebSafe } from '../../components/webSafe/TouchableOpacityWebSafe'

fails.

This happened after upgrade from 0.53.3 to 0.54

[HumanUndead]

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

[cipriancaba]

How would that work? This is a relative path in my custom components.. It's not related to any package.. Maybe I'm missing something about the @ import syntax?

[HumanUndead]

Place a packages.json file in your components folder, give it name: ‘components’
Then you can use the @ import syntax

[cipriancaba]

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..

[HumanUndead]

It will work but its up to you

[wildseansy]

@HumanUndead - I removed relative imports that go 'up' directories, using the package.json and import MyComponent from 'components/MyComponent' syntax. What do you mean by the '@ syntax' though...? I'm still getting the issue with unknown module 'undefined'. Did you have to replace ALL relative imports, including ones with './MyModule'? ...or just ones that go up 1 or more directories ('../MyModule')?

[esutton]

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

[kengjungwa]

This is a big show stopper for our team. We've been waiting for 0.54 to get Android's keyboard crash fixes but can't due to this issue. The error occurs even on our internal file import from the same directory (import * as util from './util'). Try to fix for a few days but no luck. Also already tried putting package.json in the component folder but got same error. Not sure how to use '@ syntax'. So painful to see the app crashes on users everyday. Could anyone shed some light or share any workaround? Thanks!

[seantimm]

We're blocked here as well. I had to change several of our dynamic requires into static imports but finally got blocked at a third-party library that is having the same issue. It's unclear to me if this is a Metro bundler issue, or if this is a change that libraries need to accommodate. If it's the latter, I guess I'll start digging in and making pull requests.

[wildseansy]

In case anyone was wondering, I tried 0.54.1, still same issue

[mkuczera]

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 ?

[webraptor]

Happens as well on
"react": "16.3.0-alpha.1",
"react-native": "0.54.2"

[pavel-beloborodov]

any updates?

[andrew-wagner89]

@pavel-beloborodov I opened an issue on the metro repository (here) but I can't seem to create a minimal example showing this. Does it only occur in large projects?

[andrew-wagner89]

@pavel-beloborodov seems like they found the problem and are looking into a metro fix now!

[arash-hacker]

i upgraded to 0.54 for this #18359 reason.and now this issue :|

[schlaegerz]

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'

[sibelius]

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

[cyardimci]

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.

[andrew-wagner89]

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

[tahatag]

@wildseansy saved me

[thatjuan]

@wildseansy good call. That's the issue, spot on.

[huy-lv]

@wildseansy you saved my life :)) sometime the error show on console.error not correct line, but correct filename

[mahdieh-dev]

My Error was:

Requiring unknown module "492"

The problem was in my index.js file and App.js file both! My index,js file was like:

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

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

And my App.js had the same sentences as the first and the last sentence in my index.js file. Meaning my App.js file was like:

import React, { Component } from 'react'
import {
  AppRegistry,
...,
...,
}
 My code;
.
.
AppRegistry.registerComponent('my-app', () => MyApp);

I just deleted the first line and the last line of index.js file and it worked. Meaning the index.js file of mine turned into:

import { MyApp } from './app';

Hope this help you too.

[mikehuebner]

Also seeing this issue with a node_module item that is calling a local file. However calling the file from the source (for example import {ITEM} from 'MODULE/FILE') works fine. I've trying to see if renaming the file or just moving the file helps but so far no luck. Also all of the exports within the file are named.

[michalchudziak]

The issue was referenced by a metro team: facebook/metro#152 and should be fixed with the new version of React Native.

We are going to close this issue. If it's actually still an issue with 0.59 please comment below and we can reopen it.

[gventuri]

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

[git-jr]

Sometimes cleaning and restarting can help, worked for me on android:

cd android && gradlew clean && cd .. && react-native run-android

[rdankhara]

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

[rdankhara]

For me it was problem in importing React as well

[thomashagstrom]

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

[ahsan-khan1999]

Same issue !

[abdi4]

Same here. None of the above solutions apply/work for me