DRY, WET, SPOT…What?

As an engineer, there seems to be a slew of contradicting advice on what to do about duplicate code. Never do it? Do it once then refactor? None of it really makes sense. This talk introduces a few new mindsets for reasoning about duplicate code and what to do about it.

Transcript

1. DRY, WET, SPOT…What? @samjarman • Code Camp Wellington 2024
2. @samjarman • Code Camp Welly 2024 About me • Programming for over 15 years • Worked in Christchurch, Wellington, Auckland and now Sydney • Worked in businesses small, medium and large, start ups, agencies and enterprise • Worked in iOS (ObjC, Swift), Web (React, Angular), Backend (Ruby/Rails, Javascript/node) • Engineering Manager at Cochlear - a company that builds implants for people who are born without hearing or lose their hearing which helps them get their hearing back • Work on the backend of software that surgeons, audiologist and patients/carers use
3. @samjarman • Code Camp Welly 2024 Agenda • Code Duplication – What is it? • Ways of Handling Duplication – Code Demo • Introducing SPOT • Introducing Connascence • Code Demo of Connascence • Mindsets to take away with you
4. @samjarman • Code Camp Welly 2024 Today’s Talk • The code examples are in beginner TypeScript - but the language doesn’t make a difference to the broader point of this talk • The code examples in this talk is designed for conference talk glanceability/readability not perfection • “Code Unit” - refers to a method, class, module, package, microservice • You are welcome to live tweet/x/masto-post/threet/bluesk/whatever - I’m @samjarman on everything • Thoughts are my own and do not represent my employer
5. @samjarman • Code Camp Welly 2024 Code Duplication – What is it? Code duplication is when code is repeated in the same method, class, module, application, system, or company. It is generally regarded as a code smell
6. @samjarman • Code Camp Welly 2024 Code Smell • Code Smells are when something ‘smells’ about a codebase • “Where there’s smoke, there’s fire”
7. @samjarman • Code Camp Welly 2024 Why is duplicated code bad? We are told… • When we have to change something, we have multiple places to change • We might not be able to find all the places we to change • This adds maintenance burdens to our codebase
8. @samjarman • Code Camp Welly 2024 “DRY” • Don't Repeat Yourself is a popular phrase and mindset for avoiding duplication. • Easy to understand • Easy (ish) to do • Easier to code afterwards
9. @samjarman • Code Camp Welly 2024 “YAGNI” • On the other end of the spectrum of DRY… • "YAGNI" - You Ain't Gonna Need It • Discourages over-engineering • You ain't gonna need it – you're not going to need that nice little method/package anywhere else. Don't build it.
10. @samjarman • Code Camp Welly 2024 The Spectrum DRY YAGNI
11. @samjarman • Code Camp Welly 2024 The Spectrum DRY YAGNI WET
12. @samjarman • Code Camp Welly 2024 WET • Write Everything Twice • Write everything twice and on the third time – refactor • Between DRY and YAGNI
13. @samjarman • Code Camp Welly 2024 Summary • DRY • WET • YAGNI → 3 Popular ways of thinking about avoiding coding duplication
14. @samjarman • Code Camp Welly 2024 I think they’re all wrong 󰤇
15. @samjarman • Code Camp Welly 2024 It’s just more subtle than that 😅
16. @samjarman • Code Camp Welly 2024 Duplicating code is sometimes okay 👍
17. @samjarman • Code Camp Welly 2024 → VS Code
18. @samjarman • Code Camp Welly 2024 Types of Duplication • Accidental vs Deliberate • Deliberate = These two/n things should have be the same in order to maintain system correctness ◦ When person had two implementations of nickname • Accidental = These two/n things happen to be the same for now ◦ When Doctor happened to have the same nickname as Person
19. @samjarman • Code Camp Welly 2024 Code exists through time • These two things are the same – but will they always be? • This is YAGNI but clearer
20. @samjarman • Code Camp Welly 2024 SPOT – Single Point Of Truth • Person= two points of truth for a nickname • Doctor vs Person = Two, single points of truth, one for each person …Forget DRY/WET
21. @samjarman • Code Camp Welly 2024 Coupling If I must change two places in order to keep system correctness… Then the things are “coupled”
22. Introducing Connascence
23. @samjarman • Code Camp Welly 2024 Connascence 1. The common birth of two or more at the same time. 2. That which is born or produced with another. 3. The act of growing together.
24. @samjarman • Code Camp Welly 2024 Connascence – Melir Page-Jones (1992) “Connascence is a software quality metric [...] to allow reasoning about the complexity caused by coupling”
25. @samjarman • Code Camp Welly 2024 Connascence Two software components are connascent if a change in one would require the other to be modified in order to maintain the overall correctness of the system.
26. @samjarman • Code Camp Welly 2024 Types of Connascence • Name • Type • Meaning • Position • Algorithm • Execution • Timing • Value • Identity
27. @samjarman • Code Camp Welly 2024 Types of Connascence • Name • Type • Meaning • Position • Algorithm • Execution • Timing • Value • Identity Weaker Stronger Degree Fewer More
28. @samjarman • Code Camp Welly 2024 Types of Connascence • Name • Type • Meaning • Position • Algorithm • Execution • Timing • Value • Identity Weaker Stronger Degree Fewer More Locality
29. @samjarman • Code Camp Welly 2024 Types of Connascence • Static ◦ Name ◦ Type ◦ Meaning ◦ Position ◦ Algorithm • Dynamic ◦ Execution ◦ Timing ◦ Value ◦ Identity
30. @samjarman • Code Camp Welly 2024 Static Connascence → VS Code
31. @samjarman • Code Camp Welly 2024 Ease of Change • Name of a property/method - Easy • Type of a property – Easy • Parameters of a method – Harder • Contract of a method - Hard
32. @samjarman • Code Camp Welly 2024 Dynamic Connascence • Execution • Timing • Value • Identity
33. @samjarman • Code Camp Welly 2024 Connascence of Execution • If order matters • If you need to call moduleA before moduleB, there is coupling there • Consider combining into a single module, or state machines or other techniques to go back to Connascence of Algorithm
34. @samjarman • Code Camp Welly 2024 Connascence of Timing • When the timing of the execution of multiple components is important • Similar to execution but time based • moduleA can start before or after moduleB starts but must finish before • I.e the dreaded ‘race conditions’
35. @samjarman • Code Camp Welly 2024 Connascence of Value • When two sources of data have to agree on the value of something • Multiple databases (2-way sync, integrated systems)
36. @samjarman • Code Camp Welly 2024 Connascence of Identity • When two/n resources have to be known as one in the system • Merging of resources • Keeping track of multiple identifiers for a given resource
37. @samjarman • Code Camp Welly 2024 Locality • Refers to where the code units are • Might be: ◦ Same module ◦ Same file ◦ Different technology types (database vs backend vs front end) ◦ Different code bases ◦ Different departments in the company ◦ Different companies • The further away they are the harder it is to maintain ◦ The worse the connascence
38. @samjarman • Code Camp Welly 2024 And that’s Connascence
39. @samjarman • Code Camp Welly 2024 Always aim for weaker connascence
40. @samjarman • Code Camp Welly 2024 Within a module we expect more connascence
41. @samjarman • Code Camp Welly 2024 Between modules we expect less connascence
42. @samjarman • Code Camp Welly 2024 Lowering connascence between modules makes things more cohesive
43. Ask yourself…
44. @samjarman • Code Camp Welly 2024 What else do I need to change if this changes?
45. @samjarman • Code Camp Welly 2024 Does this happen to be the same or does it have be the same?
46. @samjarman • Code Camp Welly 2024 Am I duplicating code or am I duplicating a truth?
47. @samjarman • Code Camp Welly 2024 What is the connascence here? Can I lower it?
48. @samjarman • Code Camp Welly 2024 Learn More & Thanks • Codemania 2015: Josh Robb - Connascence & Coupling https://www.youtube.com/watch?v=Ip2o4vbAK3s ◦ Some of these slides reproduced here with permission • https://en.wikipedia.org/wiki/Connascence • https://codesai.com/posts/2017/01/about-connascence
49. Thanks! @samjarman • Code Camp Wellington 2024