HTML is downloaded instead of PDF

[luckylittle]

Random links do not get redirected to the PDF, but rather to a website - it seems like protection against bots. This is the content of the website:

Almost There!

Your Download of {{ refcardz.title }} is Pending

The fix is probably to extract real Location of each PDF, like:
https://dzone.com/storage/assets/2805-rc001-gwt_style_online.pdf

instead of the origin:
https://dzone.com/asset/download/6

[luckylittle]

An example of the interstitial page randomly encountered when trying downloads:
https://dzone.com/interstitial?asset=2686617&item=333545

Skip to Download request URL:
https://dzone.com/services/internal/action/campaigns-trackClick

It has sent this kind of POST payload to it to continue:
{"item":333545,"type":"rejected","referral":"Web"}

There is also https://dzone.com/services/internal/action/analytics-sendEvent URL, but i don't believe it is required. I will soon test it.

[luckylittle]

After some further research, it's clear this will not be that easy. The interstitial's page button actually executes JavaScript (e.g. https://dz2cdn2.dzone.com/storage/pub/11369473-combined.js) on the Skip to Download button:

<a href="#" ng-click="download(campaign.itemId, 'rejected')" class="ng-binding">Skip to Download</a>

The click function is:

c.on("click",function(a,c){b.$apply(function(){k(b,{$event:c||a})})});

Go Colly does not support JavaScript execution.

One option would be to use chromedp. This example demonstrates how to evaluate JavaScript and retrieve the result.

Investigating options.