How do you even start implementimg such a spec? I know it's probably a dumb question but how would one structure their code to check all those boxes? Does it usually involve reading the entire spec, then figuring out the foundational parts and building from there? Does that work when you need multiple specs to "fit" together?
How do you make sure or even check that some code you built for some part of the spec does not interfere with something else?
I implemented a few specs in my short career but nothing even close to that. It's actually mind boggling that we manage to have all those moving parts fit together.
Other than layout and rendering, implementing HTML, ECMAScript and CSS is genuinely easy. There’s a lot of it so that it’ll take you a long time, but it’s very much not hard, because the HTML and ECMAScript specs fully spell out the algorithm, telling you exactly what you must do (or, more precisely, what you must be equivalent to doing: e.g. “implementations must act as if they used the following state machine to tokenize HTML”), so it’s largely mechanical. This is very unusual in specs. I wish it were less so.
I implemented a few specs in my short career but nothing even close to that. It's actually mind boggling that we manage to have all those moving parts fit together.