Go rules

Rules

• go_repositories
• go_repository
• new_go_repository
• go_prefix
• go_library
• cgo_library
• go_binary
• go_test

Overview

The rules should be considered experimental. They support:

• libraries
• binaries
• tests
• vendoring
• cgo

They currently do not support (in order of importance):

• build constraints/tags (//+build comments - see here))
• auto generating BUILD files
• C/C++ interoperation except cgo (swig etc.)
• race detector
• coverage
• test sharding

Setup

• Decide on the name of your package, eg. github.com/joe/project

• Add the following to your WORKSPACE file:

  git_repository(
      name = "io_bazel_rules_go",
      remote = "https://github.com/bazelbuild/rules_go.git",
      tag = "0.2.0",
  )
  load("@io_bazel_rules_go//go:def.bzl", "go_repositories")
  
  go_repositories()

• Add a BUILD file to the top of your workspace, declaring the name of your workspace using go_prefix. This prefix is used for Go's "import" statements to refer to packages within your own project, so it's important to choose a prefix that might match the location that another user might choose to put your code into.

  load("@io_bazel_rules_go//go:def.bzl", "go_prefix")
  
  go_prefix("github.com/joe/project")

• For a library github.com/joe/project/lib, create lib/BUILD, containing a single library with the special name "go_default_library." Using this name tells Bazel to set up the files so it can be imported in .go files as (in this example) github.com/joe/project/lib.

  load("@io_bazel_rules_go//go:def.bzl", "go_library")
  
  go_library(
      name = "go_default_library",
      srcs = ["file.go"]
  )

• Inside your project, you can use this library by declaring a dependency on the full Bazel name (including :go_default_library), and in the .go files, import it as shown above.

  go_binary(
      ...
      deps = ["//lib:go_default_library"]
  )

• To declare a test,

  go_test(
      name = "mytest",
      srcs = ["file_test.go"],
      library = ":go_default_library"
  )

• For instructions on how to depend on external libraries, see Vendoring.md.

FAQ

Can I still use the go tool?

Yes, this setup was deliberately chosen to be compatible with the go tool. Make sure your workspace appears under

$GOROOT/src/github.com/joe/project/

eg.

mkdir -p $GOROOT/src/github.com/joe/
ln -s my/bazel/workspace $GOROOT/src/github.com/joe/project

and it should work.

Disclaimer

These rules are not supported by Google's Go team.

go_repositories

go_repositories()

Instantiates external dependencies to Go toolchain in a WORKSPACE. All the other workspace rules and build rules assume that this rule is placed in the WORKSPACE.

go_repository

go_repository(name, importpath, commit, tag)

Fetches a remote repository of a Go project, expecting it contains BUILD files. It is an analogy to git_repository but it recognizes importpath redirection of Go.

Attributes
name	String, required A unique name for this external dependency.
importpath	String, required An import path in Go, which corresponds to the root of the target remote repository
commit	String, optional The commit hash to checkout in the repository. Note that one of either commit or tag must be defined.
tag	String, optional The tag to checkout in the repository. Note that one of either commit or tag must be defined.

new_go_repository

new_go_repository(name, importpath, commit, tag)

Fetches a remote repository of a Go project and automatically generates BUILD files in it. It is an analogy to new_git_repository but it recognizes importpath redirection of Go.

Attributes
name	String, required A unique name for this external dependency.
importpath	String, required An import path in Go, which corresponds to the root of the target remote repository
commit	String, optional The commit hash to checkout in the repository. Note that one of either commit or tag must be defined.
tag	String, optional The tag to checkout in the repository. Note that one of either commit or tag must be defined.

go_prefix

go_prefix(prefix)

Attributes

prefix

String, required Global prefix used to fully qualify all Go targets. In Go, imports are always fully qualified with a URL, eg. github.com/user/project. Hence, a label //foo:bar from within a Bazel workspace must be referred to as github.com/user/project/foo/bar. To make this work, each rule must know the repository's URL. This is achieved, by having all go rules depend on a globally unique target that has a go_prefix transitive info provider.

go_library

go_library(name, srcs, deps, data)

Attributes
name	Name, required A unique name for this rule.
srcs	List of labels, required List of Go .go (at least one) or ASM .s/.S source files used to build the library
deps	List of labels, optional List of other libraries to linked to this library target
data	List of labels, optional List of files needed by this rule at runtime.

cgo_library

cgo_library(name, srcs, copts, clinkopts, cdeps, deps, data)

Attributes
name	Name, required A unique name for this rule.
srcs	List of labels, required List of Go, C and C++ files that are processed to build a Go library. Those Go files must contain import "C". C and C++ files can be anything allowed in srcs attribute of cc_library.
copts	List of strings, optional Add these flags to the C++ compiler
clinkopts	List of strings, optional Add these flags to the C++ linker
cdeps	List of labels, optional List of C/C++ libraries to be linked into the binary target. They must be cc_library rules.
deps	List of labels, optional List of other Go libraries to be linked to this library
data	List of labels, optional List of files needed by this rule at runtime.

NOTE

srcs cannot contain pure-Go files, which do not have import "C". So you need to define another go_library when you build a go package with both cgo-enabled and pure-Go sources.

cgo_library(
    name = "cgo_enabled",
    srcs = ["cgo-enabled.go", "foo.cc", "bar.S", "baz.a"],
)

go_library(
    name = "go_default_library",
    srcs = ["pure-go.go"],
    library = ":cgo_enabled",
)

go_binary

go_binary(name, srcs, deps, data)

Attributes
name	Name, required A unique name for this rule.
srcs	List of labels, required List of Go .go (at least one) or ASM .s/.S source files used to build the binary
deps	List of labels, optional List of other Go libraries to linked to this binary target
data	List of labels, optional List of files needed by this rule at runtime.

go_test

go_test(name, srcs, deps, data)

Attributes
name	Name, required A unique name for this rule.
srcs	List of labels, required List of Go .go (at least one) or ASM .s/.S source files used to build the test
deps	List of labels, optional List of other Go libraries to linked to this test target
data	List of labels, optional List of files needed by this rule at runtime.