React Native 0.46.1 does not support import/export generator functions

Is this a bug report?

yes

Have you read the Bugs section of the Contributing to React Native Guide?

yes

Environment

1. react-native -v: 0.46.1
2. node -v: v7.10.0
3. npm -v: 4.2.0
4. yarn --version (if you use Yarn): 0.27.5

Then, specify:

1. Target Platform (e.g. iOS, Android): Android
2. Development Operating System (e.g. macOS Sierra, Windows 10): Ubuntu Linux 17.04
3. Build tools (Xcode or Android Studio version, iOS or Android SDK version, if relevant):

Steps to Reproduce

(Write your steps here:)

1. Create empty react-native project

2. Add test.js in project root with generator function export: export function* doSomething() {console.log(‘test’);} export default {test: doSomething};

3. Change index.android.js to: import React from ‘react’; import {AppRegistry, Text} from ‘react-native’; import {doSomething} from “./test”; //neither this // import doSomething from “./test”; //nor this doen’t work

class GFTest extends React.Component { render(){return <Text>hi!</Text>} } AppRegistry.registerComponent(‘gf_test’, () => GFTest);

Expected Behavior

Expected to see screen with ‘hi!’ string on it

Actual Behavior

See error screen: E/ReactNativeJS(13905): undefined is not an object (evaluating ‘regeneratorRuntime.mark’) ExceptionsManager.js:63 Cannot read property ‘mark’ of undefined handleException @ ExceptionsManager.js:63 handleError @ InitializeCore.js:125 reportFatalError @ error-guard.js:44 guardedLoadModule @ require.js:121 _require @ require.js:110 (anonymous) @ index.android.bundle…&minify=false:52122 executeApplicationScript @ debuggerWorker.js:40 (anonymous) @ debuggerWorker.js:65

E/ReactNativeJS(13905): undefined is not a function (evaluating ‘this._lazyCallableModulesname’) ExceptionsManager.js:63 this._lazyCallableModules[name] is not a function handleException @ ExceptionsManager.js:63 handleError @ InitializeCore.js:125 reportFatalError @ error-guard.js:44 __guard @ MessageQueue.js:230 callFunctionReturnFlushedQueue @ MessageQueue.js:100 (anonymous) @ debuggerWorker.js:71

Reproducible Demo

https://github.com/UlfR/gf_test

[asCii88]

@UlfR why did you close this issue? shouldn’t this be supported in the latest version? isn’t downgrading just a temporary fix?

[markusguenther]

I had the same issue and solved this by using variables.

export default function * root() {
  let sagaIndex = [
    // some sagas only receive an action
    takeLatest(StartupTypes.STARTUP, startup)
  ];

  yield sagaIndex;
};

becomes:

const rootSaga = function * root() {
  let sagaIndex = [
    // some sagas only receive an action
    takeLatest(StartupTypes.STARTUP, startup)
  ];

  yield sagaIndex;
};

export default rootSaga;