let! and subject! ordering

[docwhat]

It would be nice to have a feature/documentation for the ordering of let! and subject! since it can make a difference.

Personally, I'd prefer they were run last; after all before blocks and before the example.

e.g.

  Scenario: subject bang runs after all before blocks at latest
    Given a file named "subject_bang_last_spec.rb" with:
    """ruby
      describe "subject! runs last" do
        subject! { array.count }
        let(:array) { [] }
        before { array.push 1 }
        describe "nesting group" do
          before { array.push 2 }
          it { should eq(2) }
        end
      end
      """
    When I run `rspec subject_bang_last_spec.rb`
    Then the examples should all pass

It looks like, however, they are run first.

Ciao!

[myronmarston]

subject! and let! are very implicit constructs, that, while occasionally useful, should not be abused, and I think that if you really need things to happen in a particular order you should explicitly write it so that it happens in that order:

it 'returns the correct count' do
  array = []
  array.push 1
  array.push 2
  count = array.count
  expect(count).to eq(2)
end

There's no ambiguity here, and no room for misinterpretation.

The particular ordering you are asking for (having a subject! defined in a parent context called before a before hook in a child context) doesn't make sense with the semantics of RSpec's before hooks: we've explicitly documented that parent before hooks run before child before hooks, and subject! is simply a subject declaration plus a before hook. Changing it to act like you are requesting would break many users, and would run counter to how most people expect it to work.

[JonRowe]

👍 To what myron said. You could also order them by calling lazy lets in a before block, or chaining them together.