How works chrome.fileSystem.isRestorable?

Question

chrome.fileSystem.isRestorable is a new part of the chrome.fileSystem API and it saif if a file can be restored with its entry or not. I've made many tests but something is wrong, when I tried to do :

chrome.storage.local.get(
["recentFileId1"],
function(recent) {
  chrome.fileSystem.isRestorable(
    recent["recentFileId1"], 
    function (isRestorable){
      console.log(isRestorable);
    });
});

It returns me true, even if the file has been deleted of my computer. recentFileId1 seems like a real id (many numbers and the path at the end, for example FD158F2A41037D17440C025C1CA5FE08:question.txt) and the file's restoration works if the file is still on my computer. When I tried to restore the file with an id of a deleted file it just returns nothing, no error.

So I want to know : did I use this feature wrong or something? It can work if I try to restore and see what is restored (if it returns nothing the file has been deleted), but I don't want to use a hack if the API is available.

Thanks.

Answer 1

This function is currently only available in the dev channel of Chrome, and should be released to stable in version 31.

What you're describing sounds like a bug, please file it at http://crbug.com. We should always return true or false. What the correct behavior in this case should be is not clear.

The intent of this function is to let an app know if it should provide UI to give the user access to previously opened files. If a file is restorable, it simply means the app still has permission to access the file.

We are reserving the right to limit when files are restorable. E.g. we might have an arbitrary upper limit to how many files can be restored, or the access might timeout after a few months, or we may give the user the option of not letting apps restore any files. isRestorable lets you know if access to a previously opened file is still available.

isRestorable is not intended to give information about how accessible the file still is. Local changes can impact this - e.g. the file might be deleted or the OS access permissions changed. It might still be there but be invisible to chrome and the app due to no read access to the containing folder.

Think about a recent documents menu. This could show files which were opened and since deleted. When the app restores a deleted app it would not work and would show an error to the user. At that point the user might go to their recycle bin or git checkout and replace the file.

Or the recent documents menu could just not show files which have been deleted.

Either way your app should not rely on isRestorable as an indication of whether a file entry can be regained and successfully used, you should handle restoreFile not restoring a file and giving an error, and handle access to the file having permission problems.