# Using locally-published Glean in Fenix

Note: this substitution-based approach will not work for testing updates to glean_parser as shipped in the Glean Gradle Plugin. For replacing glean_parser in a local build, see Substituting glean_parser.

## Preparation

Clone the Glean SDK, android-components and Fenix repositories:

git clone https://github.com/mozilla/glean
git clone https://github.com/mozilla-mobile/fenix


## Substituting projects

android-components has custom build logic for dealing with composite builds, so you should be able to configure it by simply adding the path to the Glean repository in the correct local.properties file:

In fenix/local.properties:

autoPublish.glean.dir=../glean


This will auto-publish Glean SDK changes to a local repository and consume them in Fenix. You should now be able to build and run Fenix (assuming you could before all this).

## Caveats

1. This assumes you have followed the Android/Rust build setup
2. Make sure you're fully up to date in all repositories, unless you know you need to not be.
3. This omits the steps if changes needed because, e.g. Glean made a breaking change to an API used in android-components. These should be understandable to fix, you usually should be able to find a PR with the fixes somewhere in the android-component's list of pending PRs (or, failing that, a description of what to do in the Glean changelog).
4. Ask in the #glean channel on chat.mozilla.org.