def_node_matcher for explicit and implicit nil about rubocop HOT 5 CLOSED

AFAIK this is not possible with RuboCop, as it's not evaluating any code. At most, you could detect if value is a local variable, and if that local variable has been assigned the literal nil, but I would advise against that, as it doesn't seem very useful. If you must know if the method is being called with nil values, the only way to really know is to check at runtime. Another approach would be to use a type checker like Sorbet.

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RuboCop is fundamentally a static analysis tool for single files, and therefore, it cannot perform analysis across multiple files. As already mentioned, it is impossible to determine if any case, other than nil literals and local variables, is nil. So, it might be possible to ascertain the value of local variables by traversing for nodes where the value is assigned.

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This is one way I could do it but the problem here is that it fails on every type of value and not just nil.

def_node_matcher :must_equal_nil?, <<~PATTERN
            {
              (send _ :must_equal (lvar _))
              (send _ :must_equal (nil))
          }
        PATTERN

Any way to just make it work for nil values?

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I've tried several solutions, but none have worked so far. It's possible that we're dealing with a static analyzer and cannot obtain the value beforehand. I'm hoping someone from the Rubocop family can provide additional guidance.

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Yes, I have used the sorbet in some other context, which bulk up the project and I can't convince everyone to opt in for that in this case!

Thanks for the input

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