Style guide

Coding style guide and best practices

OSRD application is split in multiple services written in several languages. We try to follow general code best practices and follow specificity for each languages when required.

General rules

  • Explain what you’re doing and why.
  • Document new code with doc comments.
  • Include clear, simple tests.
  • Break work into digestible chunks.
  • Take the time to pick good names. Avoid non well-known abbreviations.
  • Control and consistency over 3rd party code reuse: Only add a dependency if it is absolutely necessary. Every dependency we add decreases our autonomy and consistency.
  • Don’t re-invent every wheel: As a counter to the previous point, don’t re-invent everything at all costs. If there is a dependency in the ecosystem that is the “de-facto” standard, we should heavily consider using it.
  • More code general recommendations in main repository
  • Ask for any help that you need!


Python code is used for some packages and integration testing.


  • As a reference for our API development we are using the Rust API guidelines. Generally, these should be followed.
  • Prefer granular imports over glob imports like diesel::*.
  • Tests are written with the built-in testing framework.
  • Use the documentation example to know how to phrase and format your documentation.
  • Use consistent comment style:
    • /// doc comments belong above #[derive(Trait)] invocations.
    • // comments should generally go above the line in question, rather than in-line.
    • Start comments with capital letters. End them with a period if they are sentence-like.
  • Use comments to organize long and complex stretches of code that can’t sensibly be refactored into separate functions.
  • Code is linted with clippy.
  • Code is formatted with fmt.


Javascript / Typescript / Front

  • When adding new files, write them in TypeScript as there is a goal to move to TypeScript.
  • Use generated endpoints from the openapi.yaml files to consume the backend.
  • Code is linted with eslint.
  • Code is formatted with prettier.
  • End-to-end tests are required for stable and critical features. Playwright is used to write these tests.
  • To write unit test use vitest.

Integration tests

  • Integration tests are written using pytest under the /tests folder.
  • Each route described in the openapi.yaml files must have an integration test.
  • Test must check both the valid and invalid response format and content.