alt Hacker News"They only coded the happy path" is software engineer for "they coded it as if nothing would ever go wrong". It is definitely not good design to do that.
There's an engineering trap/fallacy I like to call "how hard could it be". How hard could it be to build a [whatever] clone? If you find yourself thinking that, stop what you're doing, because the answer is almost always "at least an order of magnitude harder than you think."
What I meant is that most commercial software has a large number of code paths. Because it’s built incrementally, not holistically. This creates complexity and cost.
If you’ve only worked on that kind of software it’s hard to know the alternative which is to aggressively prune code paths and rework your main code.
And open source example is Quake. I rarely come across software whose inherent complexity is more than quake.