Getting started with the Kythe codebase

Instructions to build Kythe from source

Code review

All changes to Kythe must go through code review before being submitted, and each individual or corporate contributor must sign an appropriate Contributor License Agreement. Once your CLA is submitted (or if you already submitted one for another Google project), make a commit adding yourself to the AUTHORS and CONTRIBUTORS files. This commit can be part of your first Differential code review.

The Kythe team has chosen to use a Phabricator instance located at for code reviews. This requires some local setup for each developer:

Installing arcanist

ARC_PATH=~/apps/arc # path to install arcanist/libphutil

sudo apt-get install php5 php5-curl
mkdir -p "$ARC_PATH"
pushd "$ARC_PATH"
git clone
git clone

# add arc to your PATH
echo "export PATH=\"${ARC_PATH}/arcanist/bin:\$PATH\"" >> ~/.bashrc
source ~/.bashrc

cd $KYTHE_DIR  # your kythe repository root
arc install-certificate

Using arcanist

git checkout master
git checkout -b feature-name # OR arc feature feature-name
# do some changes
git add ...                    # add the changes
git commit -m "Commit message" # commit the changes
arc diff                       # send the commit for review
# go through code review in Phabricator UI...
# get change accepted

You can reply to comments in Differential inside Phabricator. To submit additional commits to that same review, just git checkout to the same branch as your original arc feature, and then either git commit to make new commits or git commit --amend to tack it on to the last existing commit. Finally, just re-run arc diff to automatically send out another review request.

After someone has accepted your diff in Phabriactor (you should see a green checkbox saying “This revision is now ready to land”). Core contributors with write access to the Kythe respository run this command from their arc feature branch to merge the change into master and push it to Github:

arc land                       # merge the change into master

Others should request that someone else land their change for them once the change has been reviewed and accepted (basically, ask a core contributor to run these commands):

# Land a reviewed change
arc patch D1234
arc land

Once landed, it should show up in github commit list.

Style formatting

Kythe C++ code follows the Google style guide. You can run clang-format to do this automatically:

clang-format -i --style=file <filename>

If you forgot to do this for a commit, you can amend it easily:

clang-format i --style=file $(git show --pretty="" --name-only <SHA1>)
git commit --amend

Contribution Ideas

Along with working off of our tasks list (and, in particular, the Wishlist), there are many ways to contribute to Kythe.

New Extractors and Indexers

Kythe is built on the idea of having a common set of tools across programming languages so Kythe is always happy to add another language to its family.

Build System Integration

In order to use Kythe’s compilation extractors, they must be given precise information about how a compilation is processed. Currently, Kythe has built-in support for Bazel and rudimentary support for CMake. Contributing support for more build systems like Gradle will greatly help the ease of use for Kythe and increase the breadth of what it can index.

User Interfaces

Kythe emits a lot of data and there are many ways to interpret/display it all. Kythe has provided a sample UI, but it currently only scratches the surface of Kythe’s data. Other ideas for visualizers include an interactive graph, a documentation browser and a source file hierarchical overview.