Should sharing zero size files be allowed?

[tomayac]

Should sharing of an opaque response be allowed?

try {
  const url = 'https://www.google.com/images/branding/googlelogo/2x/googlelogo_color_272x92dp.png';
  const blob = await fetch(url, {mode: 'no-cors'}).then(response => response.blob());
  const file = new File([blob], 'image.png');
  const data = {
    files: [file]
  };
  if (!navigator.canShare(data)) {
    throw new Error('Cannot share');
  }
  await navigator.share(data);
} catch (err) {
  console.error(err.name, err.message);
}

For this example, navigator.canShare() returns true, but the actual share operation then fails. Play with this example deployed.

Possibly related: #173

[annevk]

Why would response.blob() not throw here?

[saschanaz]

Gecko does not throw on .blob() here either, btw.

[annevk]

Yeah, I realized after posting that it likely won't fail, but the blob will be empty so you won't end up sharing anything.

[marcoscaceres]

Is just checking if the file is zero size sufficient? If yes, we could just add that check for each file (and return false).

[marcoscaceres]

Alternative: filter out all zero length files. If results in empty list of files, return false.

[marcoscaceres]

@tomayac, what do you think? Drop the empty files on the floor (and do nothing if they are all empty)? It seems like the most user friendly solution.

[saschanaz]

An empty file still has some info (the filename) so I wonder implicitly filtering it out may add some confusion.

[marcoscaceres]

Well, it depends. On MacOS's various handlers it's kinda confusing, because some apps just spin up with nothing to share (e.g., in Notes.app). The name doesn't seem to play a significant role.

Others show an empty preview of a file. In Messages.app, for example:

When normally you would see a preview:

What happens on Windows?

[saschanaz]

Looks like this when an "Share to" item is selected:

[marcoscaceres]

Ok, let's got with doing nothing here. Developer should decide and, if they so choose, filter out empty files for situations like @tomayac found. However, for certain applications (e.g., text), it could make perfect sense to share an empty text file with just a file name.