Remove submit logic from click event handler

[tilboerner]

There is no need to have submit logic take place in the on click handler. It only deals with the mouse click event, not the submit event that will follow.

Before this change, blocking the default action on the click event prevents a following submit event from taking place: form.onsubmit and other registered listeners waiting for a 'submit' will never be called.

[codecov]

Codecov Report

Merging #79 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master    #79   +/-   ##
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  Coverage     100%   100%           
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  Files           4      4           
  Lines          74     74           
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  Hits           74     74

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[codingjoe]

@tilboerner I recommend checking out this bit. I needs to still work, I don't know if it is covered in the tests tho: https://stackoverflow.com/questions/47231094/get-submit-button-value-onsubmit-event

[codingjoe]

@tilboerner how does this still work?

[tilboerner]

It still works because with the other removed line in this patch, the default action for the click event is not prevented. That default action is to cause a 'submit' event on the form. (Note that the function containing the change is not handling the submit event itself, but the click event leading up to it. Preventing its default action means no submit event gets dispatched, and not submit event handlers get called, even if we later submit the form from the prototype.)

The submit event is then handled by the form.onsubmit function which was set below, on 'DOMContentLoaded':

django-s3file/s3file/static/s3file/js/s3file.js

Lines 111 to 114 in 7e7656d

	form.onsubmit = (e) => {
	e.preventDefault()
	uploadS3Inputs(e.target)
	}

If I understand JS correctly, things proceed synchronously, and we can trust at this point that if the submit was triggered by a click, the click handler has added the hidden input to the form.

I found one caveat: When manually dispatching a click event for the button, it needs to be a MouseEvent to trigger the submit logic; a generic Event("click") triggers the click handler, but does not default to submitting the form. Without the change in this PR, any old Event would do.

However, the canonical click event is a MouseEvent, and gets dispatched as such even when triggering the button by keyboard or calling button.click(). All things considered, I think it's better to make the proposed change and honor the expectation of other submit handlers that they will be called on submit, rather than cater to code that is trying to use non-standard, non-MouseEvents to trigger submit clicks.

edit Forgot to mention @codingjoe. :)