re: Is “Defensive Programming” actually healthy? VIEW POST


Being still relatively a beginner, I would have added green as an else if, and then an error message in the else. Why? Because I’m always stumbling on unexpected bugs or behaviors that I never could have anticipated (because of lack of experience); so I’m always thinking “what could go wrong?” with every line I code.

Also, where I come from, the traffic light could be red, green, yellow, or turned off because of a power outage, so I would have thought of that specific scenario as having an important reason not to be else: green. I would do else: red, so if something unexpected comes up, the response is “stop” and not “go”.

Now, I wonder if this train of thought could be limiting my problem solving, or if by being extra-careful I’m being a better programmer? 🤔


It’s always better to be explicit. So even if you wanted to have a case for “power off” you should have a specific if statement for that. Falling through hides complexity and makes for code that looks simple but has hidden complexity. So please don’t have anything in the else other than:

  • this never pattern described in the article
  • or if you don’t have the never type (like if you’re not in TypeScript) then you should throw in the else. Like throw new Error(“unexpected scenario”)
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