Discourage using redundant `#tap`

[viralpraxis]

Some methods, when well-defined, are known to return self. Kernel#freeze is, perhaps, the most obvious example.

bad:

some_object
  .tap(&:freeze)

good:

some_object
  .freeze

Proposed implementation: rubocop/rubocop#15381

[G-Rath]

While in theory this can happen such as with your specific example, in practice it's impossible for Rubocop to report this accurately because it requires type information.

Consider e.g. [1, 2, 3].tap(&:pop) which will return the array, whereas removing the tap ([1, 2, 3].pop) would return the element that was popped.

I think in theory there could be a cool cop around tap vs then, but I think type information would need to be available for Rubocop to be able to accurately report on that

[viralpraxis]

While in theory this can happen such as with your specific example, in practice it's impossible for Rubocop to report this accurately because it requires type information.

Consider e.g. [1, 2, 3].tap(&:pop) which will return the array, whereas removing the tap ([1, 2, 3].pop) would return the element that was popped.

I think in theory there could be a cool cop around tap vs then, but I think type information would need to be available for Rubocop to be able to accurately report on that

I'm well aware of SA's type inference limitations -- this proposal is intentionally limited to methods that, when well-defined, are known to return self.

[G-Rath]

Ok, but your proposal for the style guide currently doesn't state that - I'm thinking about this from the POV of Ruby beginner who might not know what tap does all that well, and so assume based on the current version of your proposal that any version of .tap(&:method) should be replaced with .method.

[viralpraxis]

Ok, but your proposal for the style guide currently doesn't state that - I'm thinking about this from the POV of Ruby beginner who might not know what tap does all that well, and so assume based on the current version of your proposal that any version of .tap(&:method) should be replaced with .method.

Thanks, I updated the proposal.