In this talk, we want to make two major points:
- Metrics can facilitate better conversation about code quality. They help you focus more on technical problems and improvements instead of personal preferences and organizational issues.
- Metrics can be misused very easily. Knowing their limitations is crucial.
For each metric, we'll discuss:
- code examples in Python
- how to calculate
- interpretation (incl. some comparison across open source Python projects)
- You can calculate it without specific tools.
- First step: Extract functions.
- It shows well some general limitations of code quality metrics.
- Show the formula, but don't explain it in detail. :-)
- Extract functions. Remove redundant if conditions.
- It doesn't account for nested coding constructs. It ignores some modern language patterns.
- Calculation and interpretation: see https://www.sonarsource.com/docs/CognitiveComplexity.pdf
- Actions: Extract functions. Use shorthand structures. More Pythonic code is also more readable.
- Limitations: It ignores both the length of a linear block and the complexity of the expressions used in it.
Another aspect of human understanding.
- Calculation: see https://sourcery.ai/blog/working-memory/
- Interpretation: The 7 +/- 2 rule of the human working memory.
- Actions: Extract functions, some more specific refactorings this metric rewards.
- Limitations: It ignores the structure.
Limitations And Pitfalls
- They can be gamed.
- They easily encourage one-sided thinking and behaviour.
Specific For Code Quality Metrics
- Great as warning signs, not good as "proof of excellence".
Giving a more versatile picture than a single metric.
What Metrics Don't Capture
- naming, consistent terminology, ubiquitous language (DDD)
- project structure