[Dropzone] Upload same file empty the drop zone, chrome only

[nforgeot-norsys]

When you upload the same file, Chrome do not trigger change event. Firefox do. I think Chrome have the correct behavior this time.

This behavior introduced an issue in the UX dropzone. In chrome, when you upload the same file, the dropzone is emptied.

bug_dropzone_same_file.webm

---

Solution : Listen the drop event and show the drop zone if a input value is set.

What do you think of this solution ? Tested ok in Chrome and Firefox.

in https://github.com/symfony/ux/blob/v2.22.1/src/Dropzone/assets/dist/controller.js

    initialize() {
        // ...
        this.onDrop = this.onDrop.bind(this);
    }

    connect() {
        // ...
        this.element.addEventListener('drop', this.onDrop);
    }

    disconnect() {        // ...
        this.element.removeEventListener('drop', this.onDrop);
    }

    onDrop() {
        if (this.inputTarget.value === '') {
            return;
        }

        this.inputTarget.style.display = 'none';
        this.placeholderTarget.style.display = 'none';
        this.previewTarget.style.display = 'flex';
    }

If it's ok for you, I can try to do the PR ;)

[smnandre]

Hey @nforgeot-norsys ! Not 100% sur to get how the problem occurs (i probably missed something)

I had the impression that either onchage was triggerd, and current file was replaced, onchange was not triggered, so current file stayed there...

Do you have any other script involved here ?

[nforgeot-norsys]

Hey @smnandre

current file was replaced, onchange was not triggered, so current file stayed there...

Yes that it. It's Chrome behaviour. But Firefox trigger every time.

No I don't have other script involved in this behavior. I have made a little test in a sandbox to demonstrate that https://jsfiddle.net/a6jng31u/ .