Nested React Native projects result in TypeError: undefined is not an object (evaluating self.fetch)

[migueloller]

I'm unsure how related this is to #5667 or #3975 but I've been trying to figure this out for 5 hours.

Here's the repo: https://github.com/bloveit/react-native-redux-navigation

I'm trying to create a React Native example for this module but there is an error that occurs when trying to run the example.

To reproduce:

git clone https://github.com/bloveit/react-native-redux-navigation.git
cd react-native-redux-navigation
npm i
cd examples/TabsExample
npm i
react-native run-ios

I tried to pinpoint the error to a specific package, but no luck. I also tried nesting other React Native projects but the bug didn't happen (it seems to be an edge case).

Would greatly appreciate some insight on this bug!

Screenshot:

Thanks! 🍺

[migueloller]

A most peculiar thing is that if remote JS debugging is turned on, the error goes away.

[willks]

@migueloller I'm also getting this since trying to upgrade to RN 0.33 - and this is my latest issue. It works in DEBUG mode for me as well. Did you ever get around this issue?

[migueloller]

@willks,

I did not. 😞

I ended up removing the example folder completely and was going to look at the problem a bit closer at a later time.

[willks]

@migueloller Hey I got it working using RN 0.33 and doing a hack - following this project:

https://github.com/johanneslumpe/react-native-browser-polyfill

Specifically, I added the following to my app.js:

global.self = global;

I added it right at the top. Now my fetches are working properly again. Seems like a dirty hack but I was a bit desperate to get it going on iOS10 and now it's running again.

[migueloller]

@willks,

Interesting fix, I wonder if React Native should do this by itself?

[willks]

@migueloller Yeah there's a bit of powerful opinions either way so rather than wait until the respective teams make up their minds, I think the users have to solve this one on their own.

[compojoom]

I had the same issue for the past 2 months and I was always wondering what's going on.

@willks - thanks, your fix works for me as well.

[compojoom]

Actually I had to do this:

if(typeof global.self === "undefined")
{
    global.self = global;
}

because when debuging remotely I was getting: "cannot assign to read only property 'self' of object '#?"

[tqc]

This is caused by the fetch polyfill from https://github.com/github/fetch / https://www.npmjs.com/package/whatwg-fetch requiring self or this to be defined.

The workaround from other comments usually succeeds, but is not completely reliable because the packager/transpiler does not guarantee that that will run before whatever is calling fetch. Usually that isn't a problem because global.fetch is implemented as a lazy getter, but a module containing if (fetch) on startup is sufficient to trigger the bug.

[pull-bot]

Hi there! This issue is being closed because it has been inactive for a while. Maybe the issue has been fixed in a recent release, or perhaps it is not affecting a lot of people. Either way, we're automatically closing issues after a period of inactivity. Please do not take it personally!

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[apolishch]

This issue has reappeared for me when upgrading from RN0.51 to RN0.53
The workaround in this commit:
davidvuong/ddfa-rn-app@e54a799

makes the problem go away