Swift Rules for Bazel
This repository contains rules for Bazel that can be used to build Swift libraries, tests, and executables for macOS and Linux.
To build applications for all of Apple's platforms (macOS, iOS, tvOS, and watchOS), they can be combined with the Apple Rules.
If you run into any problems with these rules, please file an issue!
Click here for the reference documentation for the rules and other definitions in this repository.
Please refer to the release notes for a given release to see which version of Bazel it is compatible with.
1. Install Swift
Before getting started, make sure that you have a Swift toolchain installed.
Apple users: Install Xcode. If this is your first time installing it, make sure to open it once after installing so that the command line tools are correctly configured.
Linux users: Follow the instructions on the Swift download page to download and install the appropriate Swift toolchain for your platform. Take care to ensure that you have all of Swift's dependencies installed (such as ICU, Clang, and so forth), and also ensure that the Swift compiler is available on your system path.
2. Configure your workspace
Add the following to your
WORKSPACE file to add the external repositories,
sha256 attributes with the values from the release
you wish to depend on:
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive") http_archive( name = "build_bazel_rules_swift", sha256 = "8a49da750560b185804a4bc95c82d3f9cc4c2caf788960b0e21945759155fdd9", url = "https://github.com/bazelbuild/rules_swift/releases/download/0.25.0/rules_swift.0.25.0.tar.gz", ) load( "@build_bazel_rules_swift//swift:repositories.bzl", "swift_rules_dependencies", ) swift_rules_dependencies() load( "@build_bazel_rules_swift//swift:extras.bzl", "swift_rules_extra_dependencies", ) swift_rules_extra_dependencies()
swift_rules_dependencies macro creates a toolchain appropriate for your
platform (either by locating an installation of Xcode on macOS, or looking for
swiftc on the system path on Linux).
3. Additional configuration (Linux only)
swift_test rules expect to use
clang as the driver
for linking, and they query the Bazel C++ API and CROSSTOOL to determine which
arguments should be passed to the linker. By default, the C++ toolchain used by
gcc, so Swift users on Linux need to override this by setting the
CC=clang when invoking Bazel.
This step is not necessary for macOS users because the Xcode toolchain always
Building with Custom Toolchains
macOS hosts: You can build with a custom toolchain installed in
/Library/Developer/Toolchains instead of Xcode's default. To do so, pass the
following flag to Bazel:
toolchain.id is the value of the
CFBundleIdentifier key in the
toolchain's Info.plist file.
To list the available toolchains and their bundle identifiers, you can run:
bazel run @build_bazel_rules_swift//tools/dump_toolchains
Linux hosts: At this time, Bazel uses whichever
swift executable is
encountered first on your
Supporting remote builds
To make remote builds work correctly with debugging and general reproducibility see this doc
Swift Package Manager Support
To download, build, and reference external Swift packages as Bazel targets, check out rules_spm. The rules in rules_spm build external Swift packages with Swift Package Manager, then make the outputs available to Bazel rules.
- Support for building and linking to shared libraries (
.so) written in Swift.
- Migration to the Bazel platforms/toolchains APIs.
- Support for multiple toolchains, and support for non-Xcode toolchains on macOS.
- Automatically download a Linux toolchain from swift.org if one is not already installed.
We gratefully acknowledge the following external packages that rules_swift depends on: