Third-party code is part of the Fuchsia checkout but is neither copyrighted by the Fuchsia authors nor subject to Fuchsia's license. In other words, any code that is not 100% owned by the Fuchsia authors is managed as third-party code.
The Fuchsia project maintains copies of third-party code dependencies under the
//third_party/ directory in the checkout. This is also known as vendoring.
Vendoring ensures that third-party code is served from Fuchsia-owned source
repositories and is served at revisions that are known to work with other code
in the Fuchsia checkout.
When adding third-party code, follow the steps below to ensure the code complies with the Fuchsia project policies.
Before you start
All external code must go through the Open Source Review Board (OSRB) process to be added to the Fuchsia Platform Source Tree. Once the OSRB request is approved, continue with the steps below.
If you are adding Rust, Dart or Go dependencies, follow the guides below:
Rust: Follow the external Rust crates guide.
Dart: Follow the third-party Dart packages guide.
For all other languages, continue with the steps below.
Get the code
All external code must follow the third_party source layout below (using
googletest as example):
root [fuchsia.googlesource.com/fuchsia] third_party/ googletest/ src/ [fuchsia.googlesource.com/third_party/github.com/google/googletest] BUILD.gn OWNERS README.fuchsia
//third_party/googletest/src/ is the root of the Fuchsia-owned mirror
repository, that contains a copy of the upstream
googletest. (Note: For Python repositories,
/<module_name> to follow Python's convention. This
convention is expected by common Python tools like pyright.)
//third_party/googletest/ directory is part of the
//third_party/googletest/BUILD.gn defines build targets for the
library. Since this file belongs to
fuchsia.git (not the
googletest repository), it can be updated in
lockstep with other Fuchsia
BUILD.gn files that depend on
makes build refactors and other large-scale changes easier.
Additional files that are required to adapt the third-party code to the Fuchsia
project may be present under (in this case)
Each dependency must have an associated
OWNERS file. Because it's
fuchsia.git, it is possible to include owners from other files
elsewhere in the Fuchsia project.
The OWNERS file must either list two Fuchsia developer accounts as the first
two lines or include a
file: directive to another OWNERS file. This will ensure
accountability for maintenance of the code over time.
The OWNERS are typically the owners of the code that use the dependency, unless specified otherwise.
The dependency's OWNERS help keep Fuchsia and its users safe by: * Removing the dependency when/if it is no longer needed * Updating the dependency when a security or stability bug is fixed upstream * Helping ensure the Fuchsia feature that uses the dependency continues to use the dependency in the best way, as the feature and the dependency change over time.
You need a README.fuchsia file with information about the project from which
you're reusing code. Check out
README.fuchsia for the list
of required fields to include.
Get a review
All third-party additions and substantive changes like re-licensing need the following sign-offs:
- Get the code reviewed as instructed in the OSRB approval.
- If the third-party project is security-critical (as defined in
README.fuchsia), include someone in
email@example.com review the change.
Most third-party dependencies can follow the layout described above. However, a small fraction of dependencies that are subject to uncommon circumstances are managed differently.
Having exotic dependencies can increase complexity and maintenance costs, which are incurred by direct dependencies of the third-party code. Additionally, they add complexity to common global maintenance tasks such as:
- Performing git administration tasks.
- Updating and maintaining toolchains.
- Responding to disclosed security vulnerabilities by updating vulnerable third-party code from upstream sources.
- Refactoring build rules, such as to enforce new compile-time checks.
Please exercise careful deliberation when stepping off the beaten path.
Migrating legacy third-party code to current layout
Bringing all the existing //third_party code to the layout documented above is WIP, and contributions are welcome.
To migrate legacy third-party repositories to this layout, follow these steps:
//build/secondary/third_party/<name>. If there is more than one
BUILD.gnfile, maintain the same subtree under
- In the copied
BUILD.gnfiles, update references to paths to third-party files in the form of
//third_party/<name>/to the form of
//build/secondary/<name>, or create it if it does not exist. Review the
OWNERSfile to ensure that it follows the best practices.
//build/secondary/<name>. Review the contents of this file and ensure that the metadata is correct. In uncommon cases there are modifications made to third-party code in third-party repositories, and such changes are listed in
README.fuchsia. Local modifications will often require you to make special accommodations that are not covered in this guide.
//third_party/<name>for any other first party
.gnifiles and move those to
//build/secondary/third_party/<name>/BUILD.gn(and other files containing source paths such as
.gnifiles) to use the new source location
//third_party/<name>/src. This requires updating all sources, including directory paths and more.
Update the integration manifest.
name) of the existing third-party project at
//third_party/<name>/src, while keeping the revision unchanged. With this change merged, the Fuchsia build will switch to using the
BUILD.gnfiles from the previous step.
Move Fuchsia-specific files added in step 1 to
Now that third-party code is nested under
//third_party/<name>is part of
fuchsia.git, you can undo the transitional step 1.
Wait for the integration manifest change to merge and roll, then run
jiri update. Or stage the integration manifest change from the previous step in your local checkout, then run
jiri update -local-manifest.
BUILD.gnand other Fuchsia-specific files from
//third_party/<name>is tracked but
//third_party/<name>/srcis not tracked.
//third_party/<name>/srcinto a mirror.
//third_party/<name>/srcto track upstream such that it only has upstream changes in its
git log. You can do this by updating the integration manifest to reference an upstream commit hash.