Go rules for Bazel
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Latest commit e7400d9 Jan 17, 2017 @pmbethe09 pmbethe09 committed on GitHub change README in advance of 0.4.0 tag (#245)

README.md

Go rules

Bazel ≥0.3.1 linux-x86_64 ubuntu_15.10-x86_64 darwin-x86_64
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Overview

The rules should be considered experimental. They support:

  • libraries
  • binaries
  • tests
  • vendoring
  • cgo
  • auto generating BUILD files via gazelle
  • protocol buffers (via extension //proto:go_proto_library.bzl)

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

  • build constraints/tags (//+build comments - see here))
  • bazel-style auto generating BUILD (where the library name is other than go_default_library)
  • 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 = "0.4.0",
    )
    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, remote, 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 also provides a default value for the root of the target remote repository

remote String, optional

The root of the target remote repository, if this differs from the value of importpath

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, remote, 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 also provides a default value for the root of the target remote repository

remote String, optional

The root of the target remote repository, if this differs from the value of importpath

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.

....

go_proto_library

go_proto_library(name, srcs, deps, has_services)
Attributes
name Name, required

A unique name for the underlying go_library rule.

srcs List of labels, required

List of Protocol Buffer .proto source files used to generate .go sources for a go_library

deps List of labels, optional

List of other go_proto_library(s) to depend on. Note: this also works if the label is a go_library, and there is a filegroup {name}+"_protos" (which is used for golang protobuf)

has_services integer, optional, defaults to 0

If 1, will generate with plugins=grpc and add the required dependencies.