Should I throw on null parameters in private/internal methods?

Question

I\'m writing a library that has several public classes and methods, as well as several private or internal classes and methods that the library itself uses.

In the publi

Answer 1

Though you tagged language-agnostic, it seems to me that it probably doesn't exist a general response.

Notably, in your example you hinted the argument: so with a language accepting hinting it'll fire an error as soon as entering the function, before you can take any action.
In such a case, the only solution is to have checked the argument before calling your function... but since you're writing a library, that cannot have sense!

In the other hand, with no hinting, it remains realistic to check inside the function.
So at this step of the reflexion, I'd already suggest to give up hinting.

Now let's go back to your precise question: to what level should it be checked? For a given data piece it'd happen only at the highest level where it can "enter" (may be several occurrences for the same data), so logically it'd concern only public methods.

That's for the theory. But maybe you plan a huge, complex, library so it might be not easy to ensure having certainty about registering all "entry points".
In this case, I'd suggest the opposite: consider to merely apply your controls everywhere, then only omit it where you clearly see it's duplicate.

Hope this helps.