Bug fix for download interruption promise rejection

[sonudoo]

Resolving the issue wkh237#264. Current version doesn't throw a promise rejection upon incomplete file download to storage directly, on android. I am providing a fix by comparing the bytes downloaded with the content length.

Tested on android. Throws RNFetchBlob failed. Download interrupted upon interruption.

[jonathangreco]

This is important.

When my download file has been interrupted (lost connection) the promise is not rejected, no error are catch. So I need this to be merged.

[mifi]

Same problem here - only Android. Causing very sneaky bugs. What's preventing this from being merged?

[jonathangreco]

@Traviskn ping :)

[mifi]

One potential issue i can see is if the server doesn't respond with content length, then what will happen with this code?

[mifi]

Here's my workaround in JS code:

const res = await RNFetchBlob
  .config({ path: tmpPath })
  .fetch('GET', url);

// TODO hack to remove when https://github.com/joltup/rn-fetch-blob/pull/396/files is merged
if (Platform.OS === 'android') {
  const contentLengthStr = res.info().headers['Content-Length'];
  if (contentLengthStr) {
    const contentLength = parseInt(contentLengthStr, 10);
    if (contentLength) {
      const stat = await RNFetchBlob.fs.stat(tmpPath);
      if (stat.size !== contentLength) throw new Error('Download size was not correct, maybe interrupted');
    }
  }
}

[sonudoo]

I think rn-fetch-blob is no longer being maintained.

[Traviskn]

Sorry for the delayed review, thank you for this PR!

[Traviskn]

This seems to have caused a regression that breaks Transfer-Encoding: chunked #443

[Traviskn]

I have reverted the merge of this PR. If a new PR can be opened that handles interrupted/incomplete downloads without breaking Transfer-Encoding: chunked I'd be glad to take another look!

[sonudoo]

Sure. I will look into it and raise another PR soon. Thanks.