# rules_go **Repository Path**: mirrors_atlassian/rules_go ## Basic Information - **Project Name**: rules_go - **Description**: Go rules for Bazel - **Primary Language**: Unknown - **License**: Apache-2.0 - **Default Branch**: master - **Homepage**: None - **GVP Project**: No ## Statistics - **Stars**: 0 - **Forks**: 0 - **Created**: 2020-08-08 - **Last Updated**: 2026-01-24 ## Categories & Tags **Categories**: Uncategorized **Tags**: None ## README Go rules for Bazel_ ===================== .. All external links are here .. _Bazel: https://bazel.build/ .. |travis| image:: https://travis-ci.org/bazelbuild/rules_go.svg?branch=master :target: https://travis-ci.org/bazelbuild/rules_go .. |bazelci| image:: https://badge.buildkite.com/7ff4772cf73f716565daee2e0e6f4c8d8dee2b086caf27b6a8.svg :target: https://buildkite.com/bazel/golang-rules-go .. _gazelle: https://github.com/bazelbuild/bazel-gazelle .. _gazelle update-repos: https://github.com/bazelbuild/bazel-gazelle#update-repos .. _github.com/bazelbuild/bazel-gazelle: https://github.com/bazelbuild/bazel-gazelle .. _vendoring: Vendoring.md .. _protocol buffers: proto/core.rst .. _go_repository: https://github.com/bazelbuild/bazel-gazelle/blob/master/repository.rst#go_repository .. _go_library: go/core.rst#go_library .. _go_binary: go/core.rst#go_binary .. _go_test: go/core.rst#go_test .. _go_download_sdk: go/toolchains.rst#go_download_sdk .. _go_rules_dependencies: go/workspace.rst#go_rules_dependencies .. _go_register_toolchains: go/toolchains.rst#go_register_toolchains .. _go_proto_library: proto/core.rst#go_proto_library .. _go_proto_compiler: proto/core.rst#go_proto_compiler .. _bazel-go-discuss: https://groups.google.com/forum/#!forum/bazel-go-discuss .. _Bazel labels: https://docs.bazel.build/versions/master/build-ref.html#labels .. _#265: https://github.com/bazelbuild/rules_go/issues/265 .. _#721: https://github.com/bazelbuild/rules_go/issues/721 .. _#889: https://github.com/bazelbuild/rules_go/issues/889 .. _#1199: https://github.com/bazelbuild/rules_go/issues/1199 .. _//tests/core/cross: https://github.com/bazelbuild/rules_go/blob/master/tests/core/cross/BUILD.bazel .. _Running Bazel Tests on Travis CI: https://kev.inburke.com/kevin/bazel-tests-on-travis-ci/ .. _korfuri/bazel-travis Use Bazel with Travis CI: https://github.com/korfuri/bazel-travis .. _Travis configuration file: .travis.yml .. _rules_go and Gazelle roadmap: roadmap.rst .. _Deprecation schedule: deprecation.rst .. _Avoiding conflicts: proto/core.rst#avoiding-conflicts .. _Overriding dependencies: go/workspace.rst#overriding-dependencies .. _nogo: go/nogo.rst .. ;; And now we continue with the actual content ======== ========= Travis Bazel CI ======== ========= |travis| |bazelci| ======== ========= Mailing list: `bazel-go-discuss`_ Announcements ------------- 2019-01-23 Releases `0.16.6 `_ and `0.15.11 `_ are now available with support for Go 1.11.5 and 1.10.8. The release-0.14 is no longer receiving updates, and this is likely the last release on the 0.15 branch. 0.17.0 will be out soon. 2018-12-20 Gazelle `0.16.0 `_ is now available. 2018-12-15 Releases `0.16.5 `_, `0.15.10 `_, and `0.14.8 `_ are now available with support for Go 1.11.4 and 1.10.7. Contents -------- .. contents:: . :depth: 2 Documentation ~~~~~~~~~~~~~ * `Core API `_ * `go_binary`_ * `go_library`_ * `go_test`_ * `Workspace rules `_ * `Protobuf rules `_ * `go_proto_library`_ * `go_proto_compiler`_ * `Toolchains `_ * `Extra rules `_ * `nogo build-time code analysis `_ * `Build modes `_ Quick links ~~~~~~~~~~~ * `rules_go and Gazelle roadmap`_ * `Deprecation schedule`_ Overview -------- The rules are in the alpha stage of development. They support: * `libraries `_ * `binaries `_ * `tests `_ * vendoring_ * cgo * cross compilation * auto generating BUILD files via gazelle_ * build-time code analysis via nogo_ * `protocol buffers`_ They currently do not support (in order of importance): * bazel-style auto generating BUILD (where the library name is other than go_default_library) * C/C++ interoperation except cgo (swig etc.) * coverage Note: The latest version of these rules (0.16.6) requires Bazel ≥ 0.17.2 to work. The ``master`` branch is only guaranteed to work with the latest version of Bazel. Setup ----- * Create a file at the top of your repository named WORKSPACE and add one of the snippets below, verbatim. This will let Bazel fetch necessary dependencies from this repository and a few others. If you want to use the latest stable release, add the following: .. code:: bzl load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive") http_archive( name = "io_bazel_rules_go", urls = ["https://github.com/bazelbuild/rules_go/releases/download/0.16.6/rules_go-0.16.6.tar.gz"], sha256 = "ade51a315fa17347e5c31201fdc55aa5ffb913377aa315dceb56ee9725e620ee", ) load("@io_bazel_rules_go//go:def.bzl", "go_rules_dependencies", "go_register_toolchains") go_rules_dependencies() go_register_toolchains() If you want to use a specific commit (for example, something close to ``master``), add the following instead: .. code:: bzl load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository") git_repository( name = "io_bazel_rules_go", remote = "https://github.com/bazelbuild/rules_go.git", commit = "a390e7f7eac912f6e67dc54acf67aa974d05f9c3", ) load("@io_bazel_rules_go//go:def.bzl", "go_rules_dependencies", "go_register_toolchains") go_rules_dependencies() go_register_toolchains() You can add more external dependencies to this file later (see `go_repository`_). * Add a file named ``BUILD.bazel`` in the root directory of your project. In general, you need one of these files in every directory with Go code, but you need one in the root directory even if your project doesn't have any Go code there. * If your project can be built with ``go build``, you can `generate your build files `_ using Gazelle. If your project isn't compatible with `go build` or if you prefer not to use Gazelle, you can `write build files by hand `_. Generating build files ~~~~~~~~~~~~~~~~~~~~~~ If your project can be built with ``go build``, you can generate and update your build files automatically using gazelle_. * Add the ``bazel_gazelle`` repository and its dependencies to your WORKSPACE file before ``go_rules_dependencies`` is called. It should look like this: .. code:: bzl load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive") http_archive( name = "io_bazel_rules_go", urls = ["https://github.com/bazelbuild/rules_go/releases/download/0.16.6/rules_go-0.16.6.tar.gz"], sha256 = "ade51a315fa17347e5c31201fdc55aa5ffb913377aa315dceb56ee9725e620ee", ) http_archive( name = "bazel_gazelle", urls = ["https://github.com/bazelbuild/bazel-gazelle/releases/download/0.16.0/bazel-gazelle-0.16.0.tar.gz"], sha256 = "7949fc6cc17b5b191103e97481cf8889217263acf52e00b560683413af204fcb", ) load("@io_bazel_rules_go//go:def.bzl", "go_rules_dependencies", "go_register_toolchains") go_rules_dependencies() go_register_toolchains() load("@bazel_gazelle//:deps.bzl", "gazelle_dependencies") gazelle_dependencies() * Add the code below to the BUILD or BUILD.bazel file in the root directory of your repository. Replace the string after ``prefix`` with the prefix you chose for your project earlier. .. code:: bzl load("@bazel_gazelle//:def.bzl", "gazelle") # gazelle:prefix github.com/example/project gazelle(name = "gazelle") * After adding the ``gazelle`` rule, run the command below: :: bazel run //:gazelle This will generate a ``BUILD.bazel`` file for each Go package in your repository. You can run the same command in the future to update existing build files with new source files, dependencies, and options. Writing build files by hand ~~~~~~~~~~~~~~~~~~~~~~~~~~~ If your project doesn't follow ``go build`` conventions or you prefer not to use gazelle_, you can write build files by hand. * In each directory that contains Go code, create a file named ``BUILD.bazel`` * Add a ``load`` statement at the top of the file for the rules you use. .. code:: bzl load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library", "go_test") * For each library, add a go_library_ rule like the one below. Source files are listed in ``srcs``. Other packages you import are listed in ``deps`` using `Bazel labels`_ that refer to other go_library_ rules. The library's import path should be specified with ``importpath``. .. code:: bzl go_library( name = "go_default_library", srcs = [ "foo.go", "bar.go", ], deps = [ "//tools:go_default_library", "@org_golang_x_utils//stuff:go_default_library", ], importpath = "github.com/example/project/foo", visibility = ["//visibility:public"], ) * For each test, add a go_test_ rule like either of the ones below. You'll need separate go_test_ rules for internal and external tests. .. code:: bzl # Internal test go_test( name = "go_default_test", srcs = ["foo_test.go"], importpath = "github.com/example/project/foo", embed = [":go_default_library"], ) # External test go_test( name = "go_default_xtest", srcs = ["bar_test.go"], deps = [":go_default_library"], importpath = "github.com/example/project/foo", ) * For each binary, add a go_binary_ rule like the one below. .. code:: bzl go_binary( name = "foo", srcs = ["main.go"], deps = [":go_default_library"], ) Adding external repositories ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ For each Go repository, add a `go_repository`_ rule like the one below. This rule comes from the Gazelle repository, so you will need to load it. `gazelle update-repos`_ can generate or update these rules automatically from a go.mod or Gopkg.lock file. .. code:: bzl load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive") # Download the Go rules http_archive( name = "io_bazel_rules_go", urls = ["https://github.com/bazelbuild/rules_go/releases/download/0.16.6/rules_go-0.16.6.tar.gz"], sha256 = "ade51a315fa17347e5c31201fdc55aa5ffb913377aa315dceb56ee9725e620ee", ) # Load and call the dependencies load("@io_bazel_rules_go//go:def.bzl", "go_rules_dependencies", "go_register_toolchains") go_rules_dependencies() go_register_toolchains() # Download Gazelle http_archive( name = "bazel_gazelle", urls = ["https://github.com/bazelbuild/bazel-gazelle/releases/download/0.16.0/bazel-gazelle-0.16.0.tar.gz"], sha256 = "7949fc6cc17b5b191103e97481cf8889217263acf52e00b560683413af204fcb", ) # Load and call Gazelle dependencies load("@bazel_gazelle//:deps.bzl", "gazelle_dependencies", "go_repository") gazelle_dependencies() # Add a go repository go_repository( name = "com_github_pkg_errors", importpath = "github.com/pkg/errors", # Import path used in the .go files tag = "v0.8.1", # Specific tag, commits are also supported ) FAQ --- Can I still use the ``go`` tool? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Yes, this setup was deliberately chosen to be compatible with ``go build``. Make sure your project appears in ``GOPATH`` or has a go.mod file, and it should work. Note that ``go build`` won't be aware of dependencies listed in ``WORKSPACE``, so you may want to download your dependencies into your ``GOPATH`` or module cache so that your tools are aware of them. You may also need to check in generated files. Does this work with Go modules? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Yes, but not directly. Modules are a dependency management feature in cmd/go, the build system that ships with the Go SDK. Bazel uses the Go compiler and linker in the Go toolchain, but it does not use cmd/go. You need to describe your Go packages and executables and their dependencies in ``go_library``, ``go_binary``, and ``go_test`` rules written in build files, and you need to describe your external dependencies in Bazel's WORKSPACE file. If your project follows normal Go conventions (those required by cmd/go), you can generate and update build files using gazelle_. You can import external dependencies from your go.mod file with a command like ``gazelle update-repos -from_file=go.mod``. This will add `go_repository`_ rules to your WORKSPACE. Each `go_repository`_ rule can download a module and generate build files for the module's packages using Gazelle. See `gazelle update-repos`_ for more information. What's up with the ``go_default_library`` name? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This was used to keep import paths consistent in libraries that can be built with ``go build`` before the ``importpath`` attribute was available. In order to compile and link correctly, rules_go must know the Go import path (the string by which a package can be imported) for each library. This is now set explicitly with the ``importpath`` attribute. Before that attribute existed, the import path was inferred by concatenating a string from a special ``go_prefix`` rule and the library's package and label name. For example, if ``go_prefix`` was ``github.com/example/project``, for a library ``//foo/bar:bar``, rules_go would infer the import path as ``github.com/example/project/foo/bar/bar``. The stutter at the end is incompatible with ``go build``, so if the label name was ``go_default_library``, the import path would not include it. So for the library ``//foo/bar:go_default_library``, the import path would be ``github.com/example/project/foo/bar``. Since ``go_prefix`` was removed and the ``importpath`` attribute became mandatory (see `#721`_), the ``go_default_library`` name no longer serves any purpose. We may decide to stop using it in the future (see `#265`_). How do I access testdata? ~~~~~~~~~~~~~~~~~~~~~~~~~ Bazel executes tests in a sandbox, which means tests don't automatically have access to files. You must include test files using the ``data`` attribute. For example, if you want to include everything in the ``testdata`` directory: .. code:: bzl go_test( name = "go_default_test", srcs = ["foo_test.go"], data = glob(["testdata/**"]), importpath = "github.com/example/project/foo", ) By default, tests are run in the directory of the build file that defined them. Note that this follows the Go testing convention, not the Bazel convention followed by other languages, which run in the repository root. This means that you can access test files using relative paths. You can change the test directory using the ``rundir`` attribute. See go_test_. Gazelle will automatically add a ``data`` attribute like the one above if you have a ``testdata`` directory *unless* it contains buildable .go files or build files, in which case, ``testdata`` is treated as a normal package. How do I cross-compile? ~~~~~~~~~~~~~~~~~~~~~~~ You can cross-compile by setting the ``--platforms`` flag on the command line. For example: .. code:: $ bazel build --platforms=@io_bazel_rules_go//go/toolchain:linux_amd64 //cmd Platform-specific sources with build tags or filename suffixes are filtered automatically at compile time. You can selectively include platform-specific dependencies with ``select`` expressions (Gazelle does this automatically). .. code:: bzl go_library( name = "go_default_library", srcs = [ "foo_linux.go", "foo_windows.go", ], deps = select({ "@io_bazel_rules_go//go/platform:linux_amd64": [ "//bar_linux:go_default_library", ], "@io_bazel_rules_go//go/platform:windows_amd64": [ "//bar_windows:go_default_library", ], "//conditions:default": [], }), ) rules_go can generate pure Go binaries for any platform the Go SDK supports. If your project includes cgo code, has C/C++ dependencies, or requires external linking, you'll need to `write a CROSSTOOL file `_ for your toolchain and set the ``--cpu`` flag on the command line, in addition to setting ``--platforms``. You'll also need to set ``pure = "off"`` on your ``go_binary``. We don't fully support this yet, but people have gotten this to work in some cases. In some cases, you may want to set the ``goos`` and ``goarch`` attributes of ``go_binary``. This will cross-compile a binary for a specific platform. This is necessary when you need to produce multiple binaries for different platforms in a single build. However, note that ``select`` expressions will not work correctly when using these attributes. How do I access ``go_binary`` executables from ``go_test``? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The location where ``go_binary`` writes its executable file is not stable across rules_go versions and should not be depended upon. The parent directory includes some configuration data in its name. This prevents Bazel's cache from being poisoned when the same binary is built in different configurations. The binary basename may also be platform-dependent: on Windows, we add an .exe extension. To depend on an executable in a ``go_test`` rule, reference the executable in the ``data`` attribute (to make it visible), then expand the location in ``args``. The real location will be passed to the test on the command line. For example: .. code:: bzl go_binary( name = "cmd", srcs = ["cmd.go"], ) go_test( name = "cmd_test", srcs = ["cmd_test.go"], args = ["$(location :cmd)"], data = [":cmd"], ) See `//tests/core/cross`_ for a full example of a test that accesses a binary. Alternatively, you can set the ``out`` attribute of `go_binary`_ to a specific filename. Note that when ``out`` is set, the binary won't be cached when changing configurations. .. code:: bzl go_binary( name = "cmd", srcs = ["cmd.go"], out = "cmd", ) go_test( name = "cmd_test", srcs = ["cmd_test.go"], data = [":cmd"], ) How do I run Bazel on Travis CI? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ References: * `Running Bazel Tests on Travis CI`_ by Kevin Burke * `korfuri/bazel-travis Use Bazel with Travis CI`_ * Our own `Travis configuration file`_ In order to run Bazel tests on Travis CI, you'll need to install Bazel in the ``before_install`` script. See our configuration file linked above. You'll want to run Bazel with a number of flags to prevent it from consuming a huge amount of memory in the test environment. * ``--host_jvm_args=-Xmx500m --host_jvm_args=-Xms500m``: Set the maximum and initial JVM heap size. Keeping the same means the JVM won't spend time growing the heap. The choice of heap size is somewhat arbitrary; other configuration files recommend limits as high as 2500m. Higher values mean a faster build, but higher risk of OOM kill. * ``--bazelrc=.test-bazelrc``: Use a Bazel configuration file specific to Travis CI. You can put most of the remaining options in here. * ``build --spawn_strategy=standalone --genrule_strategy=standalone``: Disable sandboxing for the build. Sandboxing may fail inside of Travis's containers because the ``mount`` system call is not permitted. * ``test --test_strategy=standalone``: Disable sandboxing for tests as well. * ``--local_resources=1536,1.5,0.5``: Set Bazel limits on available RAM in MB, available cores for compute, and available cores for I/O. Higher values mean a faster build, but higher contention and risk of OOM kill. * ``--noshow_progress``: Suppress progress messages in output for cleaner logs. * ``--verbose_failures``: Get more detailed failure messages. * ``--test_output=errors``: Show test stderr in the Travis log. Normally, test output is written log files which Travis does not save or report. Downloads on Travis are relatively slow (the network is heavily contended), so you'll want to minimize the amount of network I/O in your build. Downloading Bazel and a Go SDK is a huge part of that. To avoid downloading a Go SDK, you may request a container with a preinstalled version of Go in your ``.travis.yml`` file, then call ``go_register_toolchains(go_version = "host")`` in a Travis-specific ``WORKSPACE`` file. You may be tempted to put Bazel's cache in your Travis cache. Although this can speed up your build significantly, Travis stores its cache on Amazon, and it takes a very long time to transfer. Clean builds seem faster in practice. How do I test a beta version of the Go SDK? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ rules_go only supports official releases of the Go SDK. However, we do have an easy way for developers to try out beta releases. In your WORKSPACE file, add a call `go_download_sdk`_ like the one below. This must be named ``go_sdk``, and it must come *before* the call to `go_register_toolchains`_. .. code:: bzl load("@io_bazel_rules_go//go:def.bzl", "go_download_sdk", "go_register_toolchains", "go_rules_dependencies", ) go_rules_dependencies() go_download_sdk( name = "go_sdk", sdks = { "darwin_amd64": ("go1.10beta1.darwin-amd64.tar.gz", "8c2a4743359f4b14bcfaf27f12567e3cbfafc809ed5825a2238c0ba45db3a8b4"), "linux_amd64": ("go1.10beta1.linux-amd64.tar.gz", "ec7a10b5bf147a8e06cf64e27384ff3c6d065c74ebd8fdd31f572714f74a1055"), }, ) go_register_toolchains() How do I get information about the Go SDK used by rules_go? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can run: ``bazel build @io_bazel_rules_go//:go_info`` which outputs ``go_info_report`` with information like the used Golang version. How do I avoid conflicts with protocol buffers? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ See `Avoiding conflicts`_ in the proto documentation. How do I use a specific version of gRPC or golang.org/x/...? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The `go_rules_dependencies`_ macro declares several external repositories at specific versions. These are needed for `go_proto_library`_ to work, especially with gRPC. See `Overriding dependencies`_ for information and an example of how to replace these repositories with different versions. Can I use a vendored gRPC with go_proto_library? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This is not supported. When using `go_proto_library`_ with the ``@io_bazel_rules_go//proto:go_grpc`` compiler, an implicit dependency is added on ``@org_golang_google_grpc//:go_default_library``. If you link another copy of the same package from ``//vendor/google.golang.org/grpc:go_default_library`` or anywhere else, you may experience conflicts at compile or run-time. If you're using Gazelle with proto rule generation enabled, imports of ``google.golang.org/grpc`` will be automatically resolved to ``@org_golang_google_grpc//:go_default_library`` to avoid conflicts. The vendored gRPC should be ignored in this case. If you specifically need to use a vendored gRPC package, it's best to avoid using ``go_proto_library`` altogether. You can check in pre-generated .pb.go files and build them with ``go_library`` rules. Gazelle will generate these rules when proto rule generation is disabled (add ``# gazelle:proto disable_global`` to your root build file).