We talk a lot about maintainability, but it often stays a gut feeling. I got curious: what if I tried to put numbers on it, using well-known metrics like coupling, cohesion and complexity?
That curiosity turned into a library: nestjs-maintainability.
What it does
It reads your NestJS source code — no booting the app, no runtime instrumentation — resolves the @Module() metadata and the DI graph, and reports metrics per module:
- Coupling — how entangled a module is with the rest of the app
- Cohesion — whether a module's dependencies stay inside it
- Complexity — how hard a typically hard function there is to read
- Size — whether one module dominates the codebase
- …and a few more
These get combined into a single 0–100 maintainability score with a letter grade.
Trying it is one command:
npx nestjs-maintainability analyze
Please don't take it too seriously
This tool was born out of curiosity. The numbers may be inaccurate, so take them as a rough reference rather than a precise measurement. Treat it as something to play with and learn from, not as a verdict on your codebase.
Feel free to try it out on your project and share what you think — I'd love to hear your impressions.
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