Handle implicit receivers in Style/InvertibleUnlessCondition

[sambostock]

Previously, we would attempt to call node.receiver.source, but node.receiver could be nil.

An error occurred while Style/InvertibleUnlessCondition cop was inspecting /path/to/file.rb:123:4.
undefined method `source' for nil

This teaches the cop to handle implicit receivers.

---

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[sambostock]

I didn't see a good way to avoid disabling this cop. It would require breaking apart this method, but I don't know that that would actually improve understandability.

Open to suggestions though.

[sambostock]

Another option might be to explicitly fallback to self as the receiver_source and then leave all the rest the same, and rely on the redundant self correction to clean it up, but I don't know if that would actually fix the complexity offense, as it still introduces the conditional, even if it's inline.

[sambostock]

I chose to do this instead of repeating the conditional

if receiver_source
  # ...
else
  # ...
end

in three places, since it's always the same logic.

I also considered receipt as the variable name. Not sure.

[bbatsov]

Any reason why you didn't go with the name receiver?

[sambostock]

I wasn't sure if that would be confusing because we would then have receiver_source and receiver, but receiver would be receiver_source + '.' or nil, not the "receiver" node, as one might expect.

I suppose another option could be dotted_receiver or dotted_receiver_source.

[bbatsov]

I see, no great options here.

[sambostock]

Yeah. I did switch¹ it to dotted_receiver_source though, since that's clearer than receive.

Footnotes

1. This change was accidentally not committed, and appears in Add missing PR feedback changes from #12711 #12722 instead. ↩

[sambostock]

I didn't add a case for an operator method, as the receiver would explicitly be self.

[bbatsov]

Might also be good to add an example in the cop's description with an implicit receiver.

[sambostock]

I've switched¹ to dotted_receiver_source, and added¹ an implicit receiver example to the documentation. 👍

Footnotes

1. These changes were accidentally not committed, and appear in Add missing PR feedback changes from #12711 #12722 instead. ↩ ↩²

[sambostock]

@bbatsov Sorry, it looks like I didn't actually push my commit doing the rename and adding the examples. 🤦

I've made the changes in #12722.