CB-14181: (android) Fix bug - Cannot read property 'filesystemName' of null

[jony89]

fix error :

Error in Success callbackId: File1539060614 : TypeError: Cannot read property 'filesystemName' of null
cordova.js:314 Uncaught TypeError: Cannot read property 'filesystemName' of null

The fsRoot might be null. reproduced with latest cordova on android emulator.

Platforms affected

What does this PR do?

What testing has been done on this change?

Checklist

• Reported an issue in the JIRA database
• Commit message follows the format: "CB-3232: (android) Fix bug with resolving file paths", where CB-xxxx is the JIRA ID & "android" is the platform affected.
  https://issues.apache.org/jira/browse/CB-14181
• Added automated test coverage as appropriate for this change.

[shazron]

There are eslint issues with this patch, see Travis CI build logs. Run npm test you will see them.

[jony89]

fixed, yet I see tests are failing and they fail in all other PR's as well.

[jcesarmobile]

This will prevent the error, but what will cause the "Cannot read property 'filesystemName' of null"? How can this be reproduced?

[jony89]

@jcesarmobile it has been reproduced to me constantly on android emulator nexus 5

device - nexus 5
android 7.1.1 nougat (yet will be reproduced on oreo as well I'm sure)
cordova 7.1.0

with the following code from the blog - documentation (caused on the line fs.root.getFile

        window.requestFileSystem(window.LocalFileSystem.TEMPORARY, 0, (fs) => {
            console.log('file system open: ' + fs.name);
            fs.root.getFile(
                `${window.cordova.file.applicationStorageDirectory}${this.fileName}`, { create: true, exclusive: false }, (fileEntry) => {
                    console.log('fileEntry is file? ' + fileEntry.isFile.toString());
                    var oReq = new XMLHttpRequest();
                    // Make sure you add the domain name to the Content-Security-Policy <meta> element.
                    oReq.open('GET', cvURL, true);
                    // Define how you want the XHR data to come back
                    oReq.responseType = 'blob';
                    oReq.onload = (oEvent) => {
                        var blob = oReq.response; // Note: not oReq.responseText
                        if (blob) {
                        // Create a URL based on the blob, and set an <img> tag's src to it.
                            var url = window.URL.createObjectURL(blob);
                            document.getElementById('bot-img').src = url;
                            // Or read the data with a FileReader
                            var reader = new FileReader();
                            reader.addEventListener('loadend', () => {
                            // reader.result contains the contents of blob as text
                            });
                            reader.readAsText(blob);
                        } else console.error('we didnt get an XHR response!');
                    };
                    oReq.send(null);
                }, function (err) { console.error('error getting file! ' + err); });
        }, function (err) { console.error('error getting persistent fs! ' + err); });

[jcesarmobile]

I couldn't reproduce with that code on real devices or the emulator.
Anyway, the code is ok, going to merge.

But what should worry us is why root is null on first place.
As you can reproduce, would be good if you can investigate and create a new issue with more information about what might cause the root to be null.