I use Chrome DevTools a lot when developing ClojureScript web applications.
I realized that a few possible DevTools tweaks would greatly improve my ClojureScript experience. For example I wanted to have integrated ClojureScript REPL directly in DevTools Javascript Console.
Chrome/Blink developers have been pretty open for adding extension points into their DevTools.
Introduction of custom formatters in early 2015 was a great step forward. This allowed to enhance presentation of ClojureScript values (data structures) directly in Javascript Console. I implemented cljs-devtools library which leverages this feature.
In December 2015 I had an idea of integrating cljs-devtools with Figwheel's REPL console. But this was not the first attempt to bring ClojureScript REPL functionality into Chrome DevTools. Actually Suprematic have implemented their ClojureScript REPL extension in 2014.
The problem with Suprematic approach for me was usability, because their REPL console was implemented as a separate extra panel. I think ClojureScript REPL should be very closely integrated with existing Javascript console. Messages from both Javascript REPL and ClojureScript REPL should be displayed together in one console.
I tried to request a new extension point which would potentially allow me to implement REPL functionality in a similar way how custom formatters are implemented. Unfortunately existing DevTools extension APIs had not been suitable for what I wanted to do. There had been some progress made on that issue but after six months of waiting I decided to fork the DevTools.
I don't have an ambition to merge this project upstream into official DevTools. Dirac changes are too specific for ClojureScript (and mostly implemented in ClojureScript). Instead, the idea is to maintain a set of patches rolling on top of official DevTools branch (and to maintain a battery of tests to make sure that the Dirac code does not break).
I also provide a Chrome Extension which wraps Dirac DevTools to make life a bit easier for Dirac users. After initial setup, the experience should be very similar to integrated DevTools - you just use a different keyboard shortcut to open it.
I view Dirac as an experimental ground where new DevTools features can be implemented in more relaxed way. Not only for ClojureScript but maybe for other compile-to-js languages as well. It could serve as a proof-of-concept implementation of some features requested in the official DevTools.
In future, it might be eventually possible to implement some Dirac features directly in the DevTools. But until then I decided to maintain a live fork so we don't have to beg Chrome developers to add ClojureScript-related features into official DevTools for us.