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Code Style Guide

This is a common baseline for coding standards suitable for all LC projects and is intended to avoid policies where many projects will reasonably disagree based on different needs and environments.

Philosophy

Goals

  1. Reduce noise in commits, code-review, etc.
  2. Make it easier for unfamiliar developers to participate
  3. Provide immediate feedback to avoid extending the development cycle

Anti-goals

  1. Creating second jobs: we will rely on automation rather than asking humans to behave like robots
  2. Picking sides in industry-wide debates without a strong consensus position

All of the recommendations in this project have been focused on providing a high benefit-to-argument ratio. When in doubt, the most important guideline is to follow the spirit of the goals rather than any particular suggestion — for example, if a particular project uses an open-source framework which has an existing style guide it is almost certainly better to follow the community practice where it conflicts with our generic guidance since that will be the most familiar to developers proficient with that tool.

In the spirit of the first anti-goal we strongly recommend relying on automation where possible. It matters far less whether you use 2 or 4 spaces to indent if your editor and other tools consistently follow that setting because the cost of following it is effectively nil if it happens automatically every time you hit save.

How this project is organized

The top-level .editorconfig file is Editor Config intended to set basic editor defaults which are intended to be suitable for all projects in all languages:

  • UTF-8 encoding
  • Unix line-termination
  • Spaces for indentation with a tab size of 4
  • Trailing whitespace is automatically trimmed (this will avoid Git highlighting extra whitespace and extra merge conflicts)

Just copy it into your project's root directory and, if your editor doesn't have native support, check for a plugin.

Where possible, configure tools to use .editorconfig rather than duplicating configuration in other files to avoid needing to synchronize customizations or exceptions.

General Practices

  • We strongly recommend the use of version control hooks and continuous integration tests for any change which can be made or tested automatically. This repository uses pre-commit to manage Git pre-commit hooks for several languages. This makes it simple to setup a new copy of the repository by running pre-commit install after the first checkout to ensure that all subsequent commits will be reformatted and validated automatically, and CI tools can use pre-commit run to run all of the configured hooks during the build process as well.

    There are a number of similar tools which provide equivalent functionality. In accordance with the philosophy above, consistency is more important than any particular tool: the part which matters most is that it's run regularly by everyone on a team with identical results.

Language-Specific Configuration

Each language has a subdirectory which contains a README file with instructions for the tools and conventions popular in that language. For example, Python tooling will assume PEP-8 but Java will reasonably differ — as always, the most important thing is consistency.

General Policies

Licensing and Third-Party Code

The Library has a long history of using and releasing open-source software and usage continues to expand. If you intend to release your project as open source please see the official release process:

https://staff.loc.gov/sites/webproduction/library-of-congress-web-policies/distribution-of-open-source-software/

All projects — whether internal and open-source — should make it easy to tell which license(s) apply to their code. The best way to do this is to avoid committing code which is not owned by the Library and instead using a package manager to download it as part of the build process. This keeps our repositories small, affirms that we are not modifying the code in question, and avoids having to document which third-part code is being redistributed and that we are legally allowed to do so.

If there is a good reason why this cannot be done, such as an upstream project which does not cleanly package its code, third-party code should be stored in a vendor directory in a directory which contains both the code and a README or LICENSE file providing context and making it clear that the Library is not claiming ownership of the code in question.