Fetch failures on Android

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Description

Fetch POST and PUT requests, to https endpoints, fail with “Network request failed”, on android simulator. We’re observing this after upgrading from 0.59.10 to 0.61.5. We can’t upgrade further (yet) given other dependencies breaking.

Observation: Adding a Header object to these requests, as opposed to empty, or JS’ empty object {}, leads to different behavior. All these requests work as-is on iOS. See simplified code samples.

React Native version: 0.61.5

Steps To Reproduce

Provide a detailed list of steps that reproduce the issue.

// works on 0.59.10. doesn't work on 0.61.5
fetch('target-url', {
    method: 'POST'
    headers: { h1: 'val1' } // fails where it used to succeed. Network Request Failed.
})

let h =  new Headers()
h.set('h1', 'val1')
fetch('target-url', {
    method: 'POST'
    headers: h // strangely succeeds.
})

Expected Results

Expect prior requests from 0.59.10, as described above, to work across iOS and Android.

Snack, code example, screenshot, or link to a repository:

See above.

[ambarc]

It’s very similar, but I think that issue might be running into broader problems. I’m trying to keep this issue open and focused on the presence of Headers being the difference between pass / fail on Android.

[therealansh]

Are you using a localhost api? If so try changing the target url to http://10.0.2.2 for android emulator and if you are trying it on a real device try changing the endpoints to your computer’s local IP address. But it is strange that it used to work before v0.61.5