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Open Knowledge Foundation Coding Standards

This document outlines coding standards for use at Open Knowledge Foundation. It is a living document, and we encourage pull request and issues to improve on or contest ideas as expressed.

Related documents

  • Code reviews: A description of our general code review process at Open Knowledge Foundation.

TL;DR

  • We use Python and Javascript (Node.js). If you plan to develop in another language please flag this and discuss.
  • Tests are required. Unit tests, as well as functional and integration tests. Aiming for test coverage of 80% and above is desirable.
    • Tests must be automated via a continuous integration platform that is triggered when code is pushed to the canonical repository.
  • Documentation is required for all code. Documentation is just as important as tests.
    • Document functions, classes, modules and packages with docstrings.
    • Provide a great README.md file with examples of how to use the code.
    • Only use documentation builders like Sphinx for large projects; prefer README.md files for brevity and accessibility of documentation.
  • Use spaces and never tabs.
    • Javascript, HTML and CSS: 2 space indentation.
    • Python: 4 space indentation.
  • Strictly enforce a 79 character line limit.
  • Lint Javascript with eslint; Lint Python using pylint.
  • Use common language conventions for naming functions, classes and variables.
  • Code should be submitted via pull requests, which another person should merge.
  • Use continuous deployment.
    • Apps should be deployed from Travis when a successful build is made on the branch used for production.
    • Packages should be published to the respective package registry when a tag is pushed.
  • Write small, reusable libraries where possible. There are many opportunities for reuse across our different products.
  • We support modern browsers. Notably, IE 10 and above. Our browser support is in sync with the browser support of Google web properties, as declared here

Languages

Our work is done in Python and Javascript (Node.js). There can be good reasons for writing a particular library or app in another language, but if you think this is the case, please raise this issue directly before starting any work.

For example apps that implement the OKF preferences, see the following:

Style and linting

Python

  1. Follow the Python Style Guide (PSG) as formulated in PEP-8: http://www.python.org/dev/peps/pep-0008/
  2. Use pylint to lint code.

The critical points are:

  • Use spaces; never use tabs
  • 4 space indentation
  • 79 character line limit
  • Variables, functions and methods should be lower_case_with_underscores
  • Classes are TitleCase

And other preferences:

  • Use ' and not " as the quote character by default
  • When writing a method, consider if it is really a method (needs self) or if it would be better as a utility function
  • When writing a @classmethod, consider if it really needs the class (needs cls) or it would be better as a utility function or factory class

Python 2/3

As a rule, all Python code should be written to support Python 2 and Python 3. There are some circumstances where, for new apps, we may want to write specifically for the Python 3 interpreter in order to take advantage of great new language features like asyncio, but at this stage, this is likely an exception and not the rule. No code should be written to be compatible with Python 2 only.

The python porting guide has great, practical advice on writing code for Python 2 and 3. Some choose to use helper libraries like six. In any case, it is strongly recommend to follow the advice from the Python porting guide and add the following snippet to all Python modules to ensure API consistency for strings, division, imports, and the print function.

# -*- coding: utf-8 -*-
from __future__ import division
from __future__ import print_function
from __future__ import absolute_import
from __future__ import unicode_literals

Javascript

  1. Use eslint to lint code.
  2. Prefer to write all new code in ES6 and compile/transpile with Webpack or Browserify. This applies to frontend and backend code. In some cases, the cost of transpilation (inflated file size) is too great (for small utility libraries), so use judgement.

The critical points are:

  • Use spaces; never use tabs
  • 2 space indentation
  • 79 character line limit
  • Variables, functions and methods should be camelCase
  • Classes are TitleCase

And other preferences:

  • Don't use semi-colons in ES6 or any code that you are transpiling - it is quite unnecessary.

Testing

Python

  1. Use tox with py.test to test code.

Javascript

  1. Use mocha to test code.
  2. Use Zombie.js or jsdom for tests that require a DOM.

Documentation

Python

Docstrings

Use Sphinx-style or Google-style documentation conventions.

User documentation

Prefer to make really good README.md files, rather than implementing a full documentation framework.

Javascript

Docstrings

Use Google-style documentation conventions.

User documentation

Prefer to make really good README.md files, rather than implementing a full documentation framework.

Frameworks

We prefer the following frameworks and libraries. If you want to use an *alternative to one of these please flag this before starting any work.

Python

  • Flask
  • Click

Javascript

  • lodash
  • Express
  • React
  • Angular

Version control

We use Git for all projects.

Branch management

We generally follow Git Flow, with some modifications, and some flexibility per project. The following should hold true for pretty much all projects:

  • Have a master branch
  • Never commit directly to master
  • Always work from a feature/{} or a fix/{} branch that is checked out from master
  • Always reference issues from Git messages using #{issue_id}, and the various other related conventions used by most Git hosts.
  • Properly describe changes in commit messages: "Fixes database migration script failure on Python 2.7", not "Fix."
  • Prefer to use the "Squash and merge" approach for pull requests using GitHub web interface

Continuous integration and deployment

All projects must be configured with a CI server. We use Travis CI by default. The CI server must run the test suite with linting.

App deployment

All apps must be deployed from the CI server.

Package publication

All packages must be published to npm and pypi from the CI server. The procedure is:

  1. Create your package and prepare it for publication.
  2. Register the package on the appropriate registry.
  3. Give the okfn user owner rights on the package.
  4. Create tags for package versions.
  5. Use the Travis integration to publish on tags.

Web apps

URLs

  • In general do not use trailing slash on urls (but ensure you redirect 301 from trailing slash to non-trailing slash)
    • e.g.: /work not /work/, /work/9 not /work/9/

RESTful APIs

  • Use plural versions of entities names for endpoints
  • When implementing RESTful APIs, keep them RESTful, but don't hesitate to create endpoints that are not RESTful when it is practical

Browser support

We support modern browsers. Notably, IE 10 and above. Our browser support is in sync with the browser support of Google web properties, as declared here

Further reading