Ask HN: How do you discover features in unknown code bases?

I'm realizing that one of the reasons why I don't do a lot of additional hobby programming is because I'm missing a fundamental skillset that I never developed (in a reliable way) over the years. I think I don't know how to discover features that I'm interested in, in code bases that I'm unfamiliar with. Example: In Chromium I want to find the algorithm that is building the DOM. I'm not sure if that is even part of the code base (https://github.com/chromium/chromium) How would you personally approach this problem?

sourcetrail is still modern. It hasn't fully bitorotted.

First you may need to find the appropriate tests, which is essentially the same problem OP describes.

It's hard. Normally I start with a word that I know is fairly unique to the domain I'm looking for (in your case maybe "cssselector"). And what you are looking for is in the Blink third party folder.

ripgrep

But to not leave a one word answer, start searching for a feature you know about and look around from where you find it. It might help to add a super small feature yourself - when it finally works, you’ll have some idea of how the code is structured and will be able to infer where other features would live if they were there. (That might take a bit more than one addition ;))

In chromium’s case, what you’re trying to do is more like reverse engineering… I’d start with a debugger.