Drake Style Guide

This repository is a fork of Google's style guide. Drake's C++ style is a small deviation from Google's, and approximately tracks Google's latest style guidance at a small delay.

The README for Google's style guide follows after some Drake-specific notes below.

Maintenance Philosophy

This style guide should be updated in two cases:

• The agreement of the Drake platform reviewers on a change to our style rules.

• A change from the upstream Google style guide which has been reviewed (and altered if necessary) by the Drake platform reviewers.

Both sorts of updates should use ordinary Reviewable review for the platform reviewer discussion.

When making a change, annotate an html tag surrounding the new material with class="drake". This makes it easy for readers to see Drake-relevant changes and for maintainers to understand our diffs. Annotate Google material that is superseded by Drake changes but is still useful for reference with class="nondrake".

When making a change, avoid changing whitespace or indentation unnecessarily. Conflict resolution is difficult in prose text, and conflicts that are just paragraph reflows make future maintainers cry.

Relevant Pages

The subset of the style guides used by Drake are:

• C++ Style Guide (aka cppguide)
• Python Style Guide (aka pyguide)

Making New Changes

Branch, edit, and PR to styleguide as you would any other Drake change.

Pull requests merged to the main branch here will not be reflected on the https://drake.mit.edu/styleguide website until you also PR to Drake to update the git sha it uses for styleguide.

See Updating Drake for more information.

Previewing Changes

See https://drake.mit.edu/documentation_instructions.html for how to preview your changes.

Pulling Upstream Changes

A Drake style guide maintainer should keep a local clone of this repository. This should be set up in the usual manner, but with remotes to both Google and Drake as you will want to (a) merge from Google and (b) rebase onto Drake updates:

• Fork "styleguide" into your account, this is where all your branches will be

  • Go to https://github.com/RobotLocomotion/styleguide and press "Fork" in the top-right corner. If prompted for the account to fork to, select your account.

• Check out your own fork

  • Go to forked repository https://github.com/**USERNAME**/styleguide and press the green "Clone or download" button, then select "ssh" and copy ssh URL

  • Clone it on your local machine:

       git clone URL_YOU_JUST_COPIED
       cd styleguide
    

• Add a "drake" remote for the Drake styleguide and make it the default upstream.

   git remote add drake https://github.com/RobotLocomotion/styleguide.git
   git remote set-url --push drake no_push
   git fetch drake
   git branch --set-upstream-to drake/main
  

• Add a "google" remote for the Drake styleguide:

   git remote add google https://github.com/google/styleguide.git
   git remote set-url --push google no_push
  

Now that you have a repository and remotes set up, you want to be up-to-date with Drake and then pull Google's changes:

git checkout main
git pull --ff-only
git checkout -b **NEW_BRANCH_NAME**
git pull google gh-pages
**RESOLVE CONFLICTS AND COMMIT**
git push --set-upstream origin **NEW_BRANCH_NAME**
**ORDINARY PR PROCESS**

There is a high likelihood that this merge will have conflicts. These conflicts represent google changes to or near Drake-specific style rules and should be considered carefully rather than accepted or rejected blindly.

When you have resolved the merge you should commit, push, and PR in the usual manner. In creating the PR, double-check that you are PR'ing against RobotLocomotion/styleguide, not google/styleguide.

You should add all of the platform reviewers to the resulting PR.

Ensure that Drake is updated. See Updating Drake for more information.

Updating Drake

Whenever a change to styleguide is made, be sure to submit a PR to drake to bump the styleguide git sha.

If there are no changes cpplint:

1. Submit styleguide PR, and follow normal review process, finally merging into the main branch of this repository.
2. Submit drake PR to bump the styleguide git sha, and follow the normal review process.

If there are changes to cpplint:

1. Submit the styleguide PR.
2. Submit the drake PR, reference the styleguide PR, and mark as do not merge.
3. Wait until drake *-release tests pass.
4. Assign review for styleguide PR. Merge once review is done.
5. Update the drake PR to use the styleguide merge commit (from the main branch; not the PR's git sha). Follow normal review process.

--

Google Style Guides

Every major open-source project has its own style guide: a set of conventions (sometimes arbitrary) about how to write code for that project. It is much easier to understand a large codebase when all the code in it is in a consistent style.

“Style” covers a lot of ground, from “use camelCase for variable names” to “never use global variables” to “never use exceptions.” This project (google/styleguide) links to the style guidelines we use for Google code. If you are modifying a project that originated at Google, you may be pointed to this page to see the style guides that apply to that project.

This project holds the C++ Style Guide, C# Style Guide, Swift Style Guide, Objective-C Style Guide, Java Style Guide, Python Style Guide, R Style Guide, Shell Style Guide, HTML/CSS Style Guide, JavaScript Style Guide, TypeScript Style Guide, AngularJS Style Guide, Common Lisp Style Guide, and Vimscript Style Guide. This project also contains cpplint, a tool to assist with style guide compliance, and google-c-style.el, an Emacs settings file for Google style.

If your project requires that you create a new XML document format, the XML Document Format Style Guide may be helpful. In addition to actual style rules, it also contains advice on designing your own vs. adapting an existing format, on XML instance document formatting, and on elements vs. attributes.

The style guides in this project are licensed under the CC-By 3.0 License, which encourages you to share these documents. See https://creativecommons.org/licenses/by/3.0/ for more details.

The following Google style guides live outside of this project: Go Code Review Comments and Effective Dart.

Contributing

With few exceptions, these style guides are copies of Google's internal style guides to assist developers working on Google owned and originated open source projects. Changes to the style guides are made to the internal style guides first and eventually copied into the versions found here. External contributions are not accepted. Pull requests are regularly closed without comment. Issues that raise questions, justify changes on technical merits, or point out obvious mistakes may get some engagement and could in theory lead to changes, but we are primarily optimizing for Google's internal needs.