Incorrect safe navigation autocorrection

[eugentorica]

if state && state.country_id != country_id
  errors.add(:state, "doesn't belong to the selected country.")
end

is automatically converted to

if state&.country_id != country_id
  errors.add(:state, "doesn't belong to the selected country.")
end

---

This is incorrect because state can be nil.
Expected behaviour: no changes required.

$ rubocop -V
Rubocop version: 0.51.0 (using Parser 2.4.0.2, running on ruby 2.4.1 x86_64-linux)

[asherkach]

The safe navigation operator, introduced in ruby 2.3.0, evaluates the left hand side of state&.country_id to nil if state is nil. Thus, the autocorrection probably doesn't change behavior as you suggest.

That said, if state and country_id are both nil, then the former adds the error while the latter does not add the error. Is this your concern?

[minyoung]

The autocorrect also triggers when I have this code: if actions && actions.length > 0

Rubocop wants to rewrite it to: if actions&.length > 0

If actions is nil, then the rewrite will result in: nil > 0, which will generate an error...

$ rubocop -V
0.51.0 (using Parser 2.4.0.2, running on ruby 2.4.1 x86_64-linux)

[asherkach]

Right. Presumably the cop should not rewrite if the result is being used in a comparison, it should only rewrite if the truthiness of falsiness of the result is being used?

[Drenmi]

I can not reproduce this using the code provided. Please add the complete output using -D, and any relevant configuration. 🙂

[Drenmi]

Was able to reproduce it now.