Download large file with a weak network connection: resolves with status 200 when the file is not fully loaded

Versions

"react": "16.6.1",
"react-native": "0.57.5",
"rn-fetch-blob": "^0.10.13"

Problem I download the file to the device. When the Internet connection is weak or the connection is broken, the file download stops. But instead of an error, RNFetchBlob’s promise successfully resolves with 200 status code and has the path to the broken file.

Actual Behavior: RNFetchBlob’s promise successfully resolves with 200 status code when file was not fully downloaded

Expected Behavior: If the connection is broken, RNFetchBlob’s promise resolves with an error and I can catch the error in the .catch block.

Code

      return new Promise((resolve, reject) => {
            RNFetchBlob
                .config({
                    // add this option that makes response data to be stored as a file,
                    // this is much more performant.
                    fileCache : true,
                    session : 'init',
                    path : path,
                    trusty : true
                })
                .fetch('get', url, {})
                .progress((received, total) => {
                    if (OfflineMapDownloadService.isDBDownloading) {
                        this.progressCallback(received/total);
                    }
                })
                .then((res) => {
                    let status = res.info().status;
                    if(status === 200) {
                        resolve(res.path());
                    } else {
                        console.log(res);
                        reject(new Error('Invalid RN-blob status ' + status));
                    }
                })
                .catch((errorMessage, statusCode) => {
                    console.log(errorMessage);
                    Sentry.captureException(new Error(errorMessage));
                    reject(errorMessage);
                });
        });

[olegmilan]

Any updates on this issue? I’m still seeing this issue on both platforms (Android and IOS). To reproduce it, I just need to turn off wifi/4g during download and it can be a small file(not necessary a big file) like image with ~1mb size

      "version": "0.10.16",
      "resolved": "https://registry.npmjs.org/rn-fetch-blob/-/rn-fetch-blob-0.10.16.tgz",
      "integrity": "sha512-hZV+nF0HK4CWmspXGMw7/G8Q8qugpS/wbKiNLsFpdBZR8XYzjFZNvBWgGyC0F5JWQn3sjmK2w/FJjBlwdQWNQg==",
      "requires": {
        "base-64": "0.1.0",
        "glob": "7.0.6"
      },

[JofBigHealth]

Note also that progress won’t always finish with totalBytes === downloadedBytes with iOS either. However, iOS doesn’t seem to have this exact problem when attempted to resume; if the connection fails to resume the native (OS) code will timeout and RBFB will report that error.

In conclusion; I don’t recommend comparing downloaded to total bytes for either platform without fixing the native code.