Remove timestamps within URLs generated by dash-renderer when soft reloading CSS

[rpkyle]

All references to ?m= have been expunged from Dash for R within plotly/dashR#201, yet this warning appears on soft reloading CSS:

I believe the cause is L35745 within dash_renderer.dev.js, which appends a CSS modification timestamp to the request coming in to the backend from the renderer:

if (a.modified > 0) {
  var link = document.createElement('link');
  link.href = "".concat(a.url, "?m=").concat(a.modified);
  link.type = 'text/css';
  link.rel = 'stylesheet';

  this._head.appendChild(link); // Else the file was deleted.
}

Assuming it's reasonable, I suggest modifying dash-renderer so that these requests are no longer made when soft reloading stylesheets.

@Marc-Andre-Rivet @alexcjohnson

[Marc-Andre-Rivet]

Combined with #1363 I would expect the renderer to not have to deal with modified timestamp and such. Instead, the reload service should return the fingerprinted css resources and a base resource name. The template could inject a data-dash-attr on link with the resource base name, the renderer would do the same. On reload the renderer can search for that instead of the url and disable the link. The new link is then created from the received fingerprinted url w/o modifications.

[chriddyp]

@rpkyle What's the downside for keeping the timestamps within the URLs? Seems harmless?

[rpkyle]

@rpkyle What's the downside for keeping the timestamps within the URLs? Seems harmless?

My understanding (and @Marc-Andre-Rivet may correct me/elaborate) is that we're addressing this sort of thing via fingerprinting now. As a result, the code referenced above is basically redundant at this point.

We could just keep it, but I think we've already elected to use a new approach going forward, so we should probably remove it.

[gvwilson]

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