Rails/RedundantPresenceValidationOnBelongsTo removes other validations on the same line

[Narnach]

The Rails/RedundantPresenceValidationOnBelongsTo cop introduced in #594 deletes entire validates statements with multiple validated attributes, when only one of them is a belongs_to reference.

I've managed to expose the underlying issue in a spec, but I'm not familiar enough (yet) with Rubocop internals to easily come up with a PR that fixes it.

---

Expected behavior

Applying Rails/RedundantPresenceValidationOnBelongsTo to this code:

belongs_to :user
validates :user, :name, presence: true

Is expected to only remove the :user validation, but leave the :name validation.

belongs_to :user
validates :name, presence: true

Actual behavior

The entire validates line is removed, causing the validation on :name to be lost.

belongs_to :user

Steps to reproduce the problem

I've created a failing spec that exposes the auto-correction bug:

it 'registers an offense when unrelated validations are present' do
  # ignore the ^^^ being misplaced to expose the correction failure
  expect_offense(<<~RUBY)
          belongs_to :user
          validates :user, :name, presence: true
                                  ^^^^^^^^^^^^^^ Remove explicit presence validation for `user`.
  RUBY

  expect_correction(<<~RUBY)
          belongs_to :user
          validates :name, presence: true
  RUBY
end

It fails due to the entire validation line getting deleted.

expected: "belongs_to :user\nvalidates :name, presence: true\n"
     got: "belongs_to :user\n"

I think the offense should only point to :user, resulting in this:

it 'registers an offense when unrelated validations are present' do
  expect_offense(<<~RUBY)
    belongs_to :user
    validates :user, :name, presence: true
              ^^^^^^^ Remove explicit presence validation for `user`.
  RUBY

    expect_correction(<<~RUBY)
    belongs_to :user
    validates :name, presence: true
  RUBY
end

RuboCop version

I encountered this in our own app after upgrading to rubocop-rails 2.13.0.
In isolation I can replicate it with the latest rubocop-rails master, 1e9c257.

$ [bundle exec] rubocop -V
1.24.0 (using Parser 3.0.3.2, rubocop-ast 1.15.0, running on ruby 3.0.3 x86_64-darwin21)
  - rubocop-performance 1.12.0
  - rubocop-rails 2.13.0
  - rubocop-rspec 2.5.0

[pirj]

Thanks for reporting, I'm working on a fix.

[pirj]

@Narnach, @texpert, @pyromaniac I've fixed this in #609, does fix your cases?

[texpert]

@Narnach, @texpert, @pyromaniac I've fixed this in #609, does fix your cases?

Yay, works like a charm!

Thanks, @pirj

[Narnach]

@Narnach, @texpert, @pyromaniac I've fixed this in #609, does fix your cases?

The test cases cover the problems I encountered and even went further by decomposing a presence/uniqueness combined case. Excellent work!