@uppy/drop-target: ignore if dropped elements aren't files

[pmusaraj]

We're using the drop-target package in Discourse, and a user noticed that nothing would happen when dragging text into an input or a textarea. I tracked this down to the

      event.preventDefault();
      event.stopPropagation();

in DropTarget's event listeners and added a check in this PR, if the dropped objects aren't files, all of DropTarget's event listeners are skipped (and the issue reported by the user is resolved).

[Murderlon]

I don't understand how the issue from the user is dragging text doesn't work, but now we add logic to also do nothing when we don't drop files?

[pmusaraj]

Thanks for your input!

Yes, when user drags text, it doesn't work because we use preventDefault and stopPropagation in the event listeners. These two calls block the default browser handling. This is useful for files (otherwise browser would open the file in a new tab), but not for text, so the proposed solution is to skip all Uppy handlers for non-files.

[Murderlon]

Alright makes sense, thanks

[Murderlon]

Seems we have some linter errors (probably from my code suggestion):

packages/@uppy/drop-target/src/index.js:

Error:    49:1   error    Expected indentation of 4 spaces but found 3                        indent
Error:    50:1   error    Expected indentation of 4 spaces but found 3                        indent