Fair enough. But even claiming that it's truly novel is not the point of the article. The point of the article is to research HTTP caching and to converse with the community about possibilities. It is not to present a new product.
In hindsight I see that the title may have been badly chosen. Before publication, none of the test readers have made any fuss about this.
> Please prove why that is impossible in VCL.
Where do you get impression that I claimed it's impossible in the VCL? It's pretty clear that the single page app approach can be replaced by edge side include, while the cookie parsing can be done with the cookie vmod.
The article claims that despite being the cache being able to do these things, application support is still required. The app has to be modified to output certain cookies in a certain format, e.g. the vary-on-user-permission-level thing. It's the combination that is important.
Have these things been done before? I'm sure they have. Most ideas in computer science are 30+ years old, and it's rare to truly find something new. But again, the point of the article is research. What we're after is not to present a new thing, but to present an idea, and if it's a new thing then we want people to help us to test; if it's not a new thing then we want to hear experiences.
It can and has been implemented with Varnish and a few lines of VCL (with support of the app as well, of course).
What is "pure varnish" anyways? Proper varnish use always needs a tuned VCL, that's the whole core of the product.
Also, if I might say, I find your edits very handwavey. Please prove why that is impossible in VCL.