plt VS Compass

I recall reading a comment on here at some point in the last year where someone who worked on a team that wrote compilers lamented the difficulty in hiring qualified people because the practice of compiler construction differs so wildly from what is taught in school or even most compiler books. Apparently it scarcely resembles what is taught in university courses based on the Dragon book or similar, both in the higher level architecture and the lower level techniques

I know that one difference is that compilers have adopted a more service-oriented architecture, kind of like the Roslyn compiler. This allows them to not only compile your code, but inform your text editor and linter and similar tooling of syntax issues incrementally.

What are other differences? Is llvm still relevant outside of academia?

Are there any books, papers, or open source projects one could study to learn how compilers are built in this day and age?

Also: does the more abstract "programming language theory" popular in the more formal functional programming world (e.g. denotational semantics, lambda calculus, Floyd-Hoare logic, type theory, etc: this sort of stuff[1]) have any relevance to compiler writers and language/language tooling developers in industry?

[1] https://steshaw.org/plt/

Programming Language Theory books and resources

steshaw/plt - A path to Programming Language Theory enlightenment

pretty much gone, the beta site seems still to be alive http://beta.compass-style.org/reference/compass/css3/ and the github repo is still about https://github.com/Compass/compass/

SASS is a CSS preprocessor that is designed to be used as a standalone preprocessor, or as part of a framework called Compass. SASS for CSS is very similar to CSS, for creating CSS files that are more easily readable and maintainable than traditional CSS files. In the next chapper, we will learn how to use SASS to create a simple CSS file.

Soon after, Chris Epstein, the creator of Compass and co-creator of Sass, forked Brandon’s repository and asked for some help with the design. Being a big fan of Chris’s, Brandon jumped on the opportunity straight away. He pulled out the content, made the theme more generic, and named his creation Octopress.

I use a CLI tool to compile it as changes are made. I use http://compass-style.org/

Compass/compass - Compass is a Stylesheet Authoring Environment that makes your website design simpler to implement and easier to maintain.