Deprecating Code Gracefully

In this post I describe a neat but simple trick that you can use to help inform developers of proposed architectural direction changes in the code they are modifying.

This is especially useful on a large, constantly evolving monolithic code base where refactors may take time and require a concerted effort across the whole team.

An example illustrates the concept quite nicely:

bundle exec rspec spec/features/deprecated_classes_spec.rb

smiley

This is a great call to action.

It encourages teams to have a conversation about the desired approach, read the docs, and collaborate where required. This may be the time to upgrade this part of the system or it maybe just fine to update the sha and carry on, assuming the relevant parties have agreed so. This change also has the benefit of showing up in a pull request and so any changes may need to be justified.

In summary, it provides an opportunity to constantly improve and share the knowledge. One of our principles at Simply Business is “maintenance is a must” and this certainly embraces that.

In Practice

Feature: Deprecated classes

As a developer
I want to raise awareness of deprecated classes
So that we don't build on code we want to refactor when we next modify it
And therefore we "do it right"

Scenario: Modifying a class which is marked as deprecated due to the new
support framework
  Given a list of deprecated files
    | file                | sha    |
    | app/support/book.rb | f92f8a |
    | app/support/page.rb | fbb220 |

  And a deprecation message:
    """
    Refactor with a goal!
    ======================
    This test fails because you have made a change to one or
    more files which we would like to deprecate in favour of
    our preferred design approach.

    Please consult with the guidelines here
    http://example.com/refactor or talk to the 'Acme' group
    within the company for guidance.
    """
  When any of the files is detected as being modified
  Then this test will fail with a deprecation message`

Step file

step "a list of deprecated files" do | files |
  @files = files.to_h
  @files.delete('file')
end

step "a deprecation message:" do | msg |
  @msg = msg
end

step "any of the files is detected as being modified" do
  @expected =
    @files.keys.each_with_object({}) do | filename, current_shas |
     contents = File.read(File.expand_path(File.join
       (__dir__,'..','..',filename)))
     current_shas[filename] = Digest::SHA1.hexdigest(contents)
   end
end

step "this test will fail with a deprecation message" do
  expect( @expected ).to match( @files ), @msg
end

You can view the full source for the example on the Github repository.