Do Repeat Yourself

It's the moment of validation for our choices of the past. The indisputable proof we made the right choice. :muscle:

In this case it was worth the time that was invested into the refactor. It made our lives easier when change was needed.

A bad abstraction

But in other cases creating an abstraction that looks very similar to the abstraction above, can make our lives harder.

Let's take a look at an example.

Once again we extract some duplication between two classes into a helper function while simultaneously dreaming of the moment of validation — which will surely arrive soon. We wait a while and surely enough, the business changes again. Of course, now we need to update the software.

We refine the change and give it quite a low estimate, as we expect to be able to easily implement the change. This is part of the clean code territory in the project after all! 🎉

But instead of being met with the happy experience of convenience, we notice that it's now a little harder to add the new business rules than before.

Apparently, only the behaviour of one of the two original classes needs to be changed. As we already invested the time to create this beautiful abstraction, we absolutely can't revert back to the old ways. That would feel _bad_, since then we would be admitting we made the wrong choice in the past. :thinking_face:

So we decide to just add a parameter to the extracted function. I mean, just one more function parameter is still readable. We can implement this change pretty quickly. Nothing wrong with just a single parameter, right? And anyway, we might be able to benefit from the abstraction in the future.

And today, a bad abstraction was born.

And the 6 other engineers that touched the code after us? They will surely keep the abstraction in place. Someone spent effort on creating this abstraction, so it should be there for a good reason! Undoing this work and going back to the original duplication sounds like madness, it'd be almost insulting to the person who created it.

So some of them add a few positional parameters, others add parameters with default values and the last one even adds a few keyword arguments:

The code is DRYer than the Sahara at high noon, but the cycle goes on, and on, and on...