[60.3] fetch issue [unable to parse json, unexpected token in json at position 1]

[MasoudAlali]

React Native version:
0.60.3

Steps To Reproduce

1. upgrade react native to 0.60.3 and clean node modules and install it again
2. send a request with fetch

there will be error like this:
unexpected token o in json at position 1

and I investigated for issue and it happens because in whatwg-fetch library
in line 492 support.blob will be true and the response from xhr will be Blob
so in fetch response.json() will fail because response is Blob not stringified json

there are some hotfixes, but I don't know exact solution for this

[kbrandwijk]

This seems rather major, with basic fetch functionality just being completely broken after spending a lot of time on the 0.60 upgrade. Looking forward to an ETA on this.
In the meantime, I'd also take a hotfix, I haven't been able to find one yet.

[MasoudAlali]

This seems rather major, with basic fetch functionality just being completely broken after spending a lot of time on the 0.60 upgrade. Looking forward to an ETA on this.
In the meantime, I'd also take a hotfix, I haven't been able to find one yet.

you can somehow disable blob support in your project, because in whatwg-fetch it's checking support.blob :)
it's not good one but you can temporary do global.Blob = null in your init

[kennym]

Experiencing the same problem in 0.60.4

/cc @lklepner

[bockc]

just updated to RN 0.60.4, I can confirm that I receive a blob when I used to receive a stringified json before. Fetch is unusable in its current state, thus making RN 0.60.4 unusable aswell. I will wait for a fix

[asurare]

Same issue for me on RN 0.60.4 as well. Did not find any viable solution yet.

[kbrandwijk]

I tried the global.Blob workaround, and it seemed to work fine in debug mode, but somehow does not work in release mode...

[chubillkelvin]

I encountered the same problem in my project.

For some reason, I managed to fix this (and I still cannot explain what happened) by downgrading some dependencies and clean build the app again.

Here's the dependencies I changed:
@react-native-community/async-storage 1.6.1 --> 1.5.1
react-native-device-info 2.3.0 --> 2.2.2
react-native-linear-gradient 2.5.6 --> 2.5.5
@babel/plugin-proposal-decorators 7.4.4 --> 7.2.0
react-test-renderer 16.8.6 --> removed

I don't exactly know which one fixed my problem, but it works for me now. Hope this helps whoever is struggling with this problem.

My react-native version is 0.60.4 and react version is 16.8.6.

[rshaikhcornerstone]

I am getting just this warning
{"line":"24531", "coloumn":"31", "sourceURL":"http://10.0.2.2:8081/index.bundle?platform=android&dev=true&minify=false"}

[kennym]

fetch stops working for us after using a AsyncStorage.setItem operation in 0.60.4, if we skip that, fetch works as expected.

We have posted a reproducible test scenario here: react-native-async-storage/async-storage#174

We are not entirely sure if this is something that has to be fixed on the react-native or on the async-storage side, but this defect started happening with 0.60.x, which is why I'm linking this thread.

Hoping for some insightful feedback.