Missing feature : BlobModule

[sm2017]

Environment

1. react-native -v:
   react-native-cli: 2.0.1
   react-native: 0.49.5

2. npm ls rnpm-plugin-windows:
   rnpm-plugin-windows@0.2.8

3. npm ls react-native-windows:
   react-native-windows@0.49.0-rc.2

4. node -v:
   v8.1.3

5. npm -v:
   5.0.3

6. yarn --version:
   1.2.0

Then, specify:

• Target Platform:
  UWP

• Target Platform Version(s):
  10.0.14393

• Target Device(s):
  Desktop

• Development Operating System:
  Windows 10

• Visual Studio Version:
  Visual Studio 2017

Steps to Reproduce

First see facebook/react-native#16585

After fixing Blob issue , in windows I get new error

TypeError: Cannot read property 'createFromParts' of undefined
at new Blob (node_modules\react-native\Libraries\Blob\Blob.js:99)

BlobModule is not implemented

Expected Behavior

see facebook/react-native#16585

Actual Behavior

As BlobModule is not implemented . fetch API is missing arraybuffer function for response

[rozele]

@sm2017 I plan to help with this, but it looks like there's a coming change to the Blob module - facebook/react-native#11573 - and I want to wait until that lands to make it work. I understand that not having a Blob module blocks from a performance perspective, but is the missing feature actually causing exceptions? The framework should fallback to base64 blobs (which should work fine on react-native-windows) if the native BlobModule is missing. Can you confirm and provide a repro if any exceptions are thrown?

[sm2017]

Actually there is no exception in react-native-windows and in this line catch exception https://github.com/github/fetch/blob/master/fetch.js#L16 . But according to https://developer.mozilla.org/en-US/docs/Web/API/Response

Response implements Body, so it also has the following methods available to it:

Body.arrayBuffer()
Takes a Response stream and reads it to completion. It returns a promise that resolves with an ArrayBuffer.
Body.blob()
Takes a Response stream and reads it to completion. It returns a promise that resolves with a Blob.
Body.formData()
Takes a Response stream and reads it to completion. It returns a promise that resolves with a FormData object.
Body.json()
Takes a Response stream and reads it to completion. It returns a promise that resolves with the result of parsing the body text as JSON.
Body.text()
Takes a Response stream and reads it to completion. It returns a promise that resolves with a USVString (text).

And according to https://github.com/github/fetch/blob/master/fetch.js#L240-L265 , here we just missing Body.arrayBuffer() and Body.blob() . and there is no alternative base64 method

So if you use arrayBuffer method we have TypeError: undefined is not a function

I will provide a repo asap

[rozele]

@sm2017 can you write up a simple component that repro's this so I can use it to see what we can do in the meantime until facebook/react-native#11573 lands?

[sm2017]

Here is a simple component that repro's this

import React, { Component } from 'react';
import {
  Text,
} from 'react-native';


export default class App extends Component {

  async componentDidMount() {
    const fetchResponse = await fetch('https://postman-echo.com/post', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/octet-stream',
      },
     body: new Uint8Array([1,2,3,4,5,6,7,8,9,0]),
    });

   const fetchResponseBody = await fetchResponse.arrayBuffer();
  }

  render() {
    return (
        <Text>
          Open console and see logs
        </Text>
    );
  }
}

If you see https://github.com/facebook/react-native/pull/16585/files I add a =[] to constructor , But for current component we have another new issue , Please see facebook/react-native#16670

For windows another issue is https://github.com/facebook/react-native/blob/master/Libraries/Blob/Blob.js#L21 and https://github.com/facebook/react-native/blob/master/Libraries/Blob/Blob.js#L102

[sm2017]

@rozele What must we do?

We are not investing in new features or lower priority bug fixes on vCurrent. The bulk of investment is now in vNext as we prepare to make that the default choice. If this issue is still relevant on the vNext implementation please open a vNext issue. If this issue is of significant severity for a vCurrent app and vNext is not an option, re-open with justification.