CUPID - for joyful coding

Some codebases are nicer to work with than others. This is true for applications, services, libraries, frameworks, even programming languages themselves. Is this a purely personal choice or are there universal characteristics of software that can make code a joy to work with?

Daniel has been thinking about this for a long time, especially since he poked a stick at the SOLID principles for fun a few years ago and people came after him with pitchforks. His recent post about why he feels SOLID is outdated ended up on the front page of Hacker News!

Now he has codified his thoughts into his own pithy five-letter acronym, CUPID: Composable, Unix philosophy, Predictable, Idiomatic, Domain-based.

Why these characteristics, what do they mean, and why should you care? Can they improve your coding experience or is this just more programmer navel-gazing?

Transcript

1. CUPID – for joyful coding Daniel Terhorst-North @tastapod
2. Motivation: not so SOLID 1. PubConf - poking the bear 2. Extreme Tuesday Club - accepting a challenge 3. Online conferences - working to a deadline! @tastapod
3. One(ish) year later… @tastapod
4. Literally on the radar @tastapod
5. Spiky traffic is spiky! @tastapod
6. Setting the scene @tastapod
7. Who are we writing code for? “Any fool can write code that a computer can understand. Good programmers write code that humans can understand.” – Martin Fowler @tastapod
8. Who are we writing code for? “Any fool can write code that a computer can understand. Good programmers write code that humans can understand.” – Martin Fowler @tastapod Can we do better than understand?
9. “Habitability is the characteristic of source code that enables [people] to understand its construction and intentions and to change it comfortably and confidently. “Habitability makes a place liveable, like home.” – Richard P. Gabriel @tastapod
10. Habitable sounds better! What about joyful? Think about a codebase that is joyful to work with Can we describe what makes it joyful? What kind of properties does joyful code have? @tastapod
11. Properties over Principles Principles are rules or guidelines - They define conditions or boundaries - Your code either conforms to the conditions or it is wrong Properties are qualities or characteristics - They define a goal or centre to move towards - Your code is only ever closer to or further from the centre @tastapod
12. Properties for properties Practical - easy to articulate, easy to assess, easy to adopt Human - from the perspective of people, not code Layered - guidance for beginners, nuance for the more experienced @tastapod
13. CUPID – for joyful coding @tastapod Composable – plays well with others Unix philosophy – does one thing well Predictable – does what you expect Idiomatic – feels natural Domain-based – in language and structure
14. Composable Code that is easy to use gets used, and used, and used! Small “surface area” - less to learn, less to go wrong, less to conflict Intention-revealing name and purpose - easy to discover, easy to evaluate Minimal dependencies - “You wanted a banana but you got a whole gorilla” – Joe Armstrong CUPID @tastapod
15. Unix philosophy “Make each program do one thing well” – and only one thing - ls lists file details (but it doesn’t inspect files!) Together with composability, there is nothing you can’t do! - “Expect the output of every program to become the input to another” - cat | grep | sed | sort | uniq | … Different from SRP - about what the code does, not how the code changes CUPID @tastapod
16. Predictable Behaves as expected, with no surprises - “Passes all tests” – Kent Beck - even when there are no tests! Deterministic - does the same thing every time - well-understood operating characteristics Observable - in the technical sense – internal state can be inferred from outputs - instrumentation, telemetry CUPID @tastapod
17. Idiomatic Uses language idioms - standard features, constructs, libraries, frameworks, tools - feels natural to work with, goes with the grain Uses local idioms - house style: coding/design standards*, or de facto - aligned with project, dependencies, platforms, organisation * caution: may not exist! You can only write idiomatic code if you learn the idioms! CUPID @tastapod
18. Domain-based Uses domain language - “Code in the language of the domain” – 97 Things Every Programmer Should Know J - and remember, there are multiple domains Uses domain structure - Code for the solution, not the framework - payments, loans, onboarding not models, views, controllers Uses domain boundaries - as module boundaries, units of deployment CUPID @tastapod
19. CUPID – for joyful coding Composable – plays well with others Unix philosophy – does one thing well Predictable – does what you expect Idiomatic – feels natural Domain-based – in language and structure @tastapod
20. CUPID applied Lens for assessing a codebase Basis for a “Code Critique” Deciding where to start with scary legacy code Syllabus for a programming course @tastapod
21. And we’re live… @tastapod
22. Share your stories! https://groups.io/g/cupid-joyful-code https://dannorth.net daniel@dannorth.net @tastapod