Go rules

Rules

• 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 tags
• auto generated 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 = "0.0.3",
  )
  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. It is strongly recommended that the prefix is not empty.

  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

  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

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

• In this case, import the library as github.com/joe/project/lib.

• For vendored libraries, you may depend on //lib/vendor/github.com/user/project:go_default_library. Vendored libraries should have BUILD files like normal libraries.

• To declare a test,

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

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_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.