Core Go rules

These are the core go rules, required for basic operation. The intent is that these rules are sufficient to match the capabilities of the normal go tools.

Additional resources


Introduction

Three core rules may be used to build most projects: go_library, go_binary, and go_test.

go_library builds a single package. It has a list of source files (specified with srcs) and may depend on other packages (with deps). Each go_library has an importpath, which is the name used to import it in Go source files.

go_binary also builds a single main package and links it into an executable. It may embed the content of a go_library using the embed attribute. Embedded sources are compiled together in the same package. Binaries can be built for alternative platforms and configurations by setting goos, goarch, and other attributes.

go_test builds a test executable. Like tests produced by go test, this consists of three packages: an internal test package compiled together with the library being tested (specified with embed), an external test package compiled separately, and a generated test main package.

Rules

Rules

go_binary

This builds an executable from a set of source files, which must all be in the main package. You can run the binary with bazel run, or you can build it with bazel build and run it directly.

Note: name should be the same as the desired name of the generated binary.

Providers:

  • [GoLibrary]
  • [GoSource]
  • [GoArchive]

name

A unique name for this target.

basename

The basename of this binary. The binary basename may also be platform-dependent: on Windows, we add an .exe extension.

cdeps

The list of other libraries that the c code depends on. This can be anything that would be allowed in [cc_library deps] Only valid if cgo = True.

cgo

If True, the package may contain [cgo] code, and srcs may contain C, C++, Objective-C, and Objective-C++ files and non-Go assembly files. When cgo is enabled, these files will be compiled with the C/C++ toolchain and included in the package. Note that this attribute does not force cgo to be enabled. Cgo is enabled for non-cross-compiling builds when a C/C++ toolchain is configured.

clinkopts

List of flags to add to the C link command. Subject to ["Make variable"] substitution and [Bourne shell tokenization]. Only valid if cgo = True.

copts

List of flags to add to the C compilation command. Subject to ["Make variable"] substitution and [Bourne shell tokenization]. Only valid if cgo = True.

cppopts

List of flags to add to the C/C++ preprocessor command. Subject to ["Make variable"] substitution and [Bourne shell tokenization]. Only valid if cgo = True.

cxxopts

List of flags to add to the C++ compilation command. Subject to ["Make variable"] substitution and [Bourne shell tokenization]. Only valid if cgo = True.

data

List of files needed by this rule at run-time. This may include data files needed or other programs that may be executed. The [bazel] package may be used to locate run files; they may appear in different places depending on the operating system and environment. See [data dependencies] for more information on data files.

deps

List of Go libraries this package imports directly. These may be go_library rules or compatible rules with the [GoLibrary] provider.

embed

List of Go libraries whose sources should be compiled together with this binary's sources. Labels listed here must name go_library, go_proto_library, or other compatible targets with the [GoLibrary] and [GoSource] providers. Embedded libraries must all have the same importpath, which must match the importpath for this go_binary if one is specified. At most one embedded library may have cgo = True, and the embedding binary may not also have cgo = True. See [Embedding] for more information.

embedsrcs

The list of files that may be embedded into the compiled package using //go:embed directives. All files must be in the same logical directory or a subdirectory as source files. All source files containing //go:embed directives must be in the same logical directory. It's okay to mix static and generated source files and static and generated embeddable files.

gc_goopts

List of flags to add to the Go compilation command when using the gc compiler. Subject to ["Make variable"] substitution and [Bourne shell tokenization].

gc_linkopts

List of flags to add to the Go link command when using the gc compiler. Subject to ["Make variable"] substitution and [Bourne shell tokenization].

goarch

Forces a binary to be cross-compiled for a specific architecture. It's usually better to control this on the command line with --platforms.

This disables cgo by default, since a cross-compiling C/C++ toolchain is rarely available. To force cgo, set pure = off.

See [Cross compilation] for more information.

goos

Forces a binary to be cross-compiled for a specific operating system. It's usually better to control this on the command line with --platforms.

This disables cgo by default, since a cross-compiling C/C++ toolchain is rarely available. To force cgo, set pure = off.

See [Cross compilation] for more information.

gotags

Enables a list of build tags when evaluating [build constraints]. Useful for conditional compilation.

importpath

The import path of this binary. Binaries can't actually be imported, but this may be used by [go_path] and other tools to report the location of source files. This may be inferred from embedded libraries.

linkmode

Determines how the binary should be built and linked. This accepts some of the same values as go build -buildmode and works the same way.

  • `normal`: Builds a normal executable with position-dependent code.
  • `pie`: Builds a position-independent executable.
  • `plugin`: Builds a shared library that can be loaded as a Go plugin. Only supported on platforms that support plugins.
  • `c-shared`: Builds a shared library that can be linked into a C program.
  • `c-archive`: Builds an archive that can be linked into a C program.

msan

Controls whether code is instrumented for memory sanitization. May be one of on, on, or auto. Not available when cgo is disabled. In most cases, it's better to control this on the command line with --@io_bazel_rules_go//go/config:msan. See [mode attributes], specifically [msan].

out

Sets the output filename for the generated executable. When set, go_binary will write this file without mode-specific directory prefixes, without linkmode-specific prefixes like "lib", and without platform-specific suffixes like ".exe". Note that without a mode-specific directory prefix, the output file (but not its dependencies) will be invalidated in Bazel's cache when changing configurations.

pure

Controls whether cgo source code and dependencies are compiled and linked, similar to setting CGO_ENABLED. May be one of on, off, or auto. If auto, pure mode is enabled when no C/C++ toolchain is configured or when cross-compiling. It's usually better to control this on the command line with --@io_bazel_rules_go//go/config:pure. See [mode attributes], specifically [pure].

race

Controls whether code is instrumented for race detection. May be one of on, on, or auto. Not available when cgo is disabled. In most cases, it's better to control this on the command line with --@io_bazel_rules_go//go/config:race. See [mode attributes], specifically [race].

srcs

The list of Go source files that are compiled to create the package. Only .go and .s files are permitted, unless the cgo attribute is set, in which case, .c .cc .cpp .cxx .h .hh .hpp .hxx .inc .m .mm files are also permitted. Files may be filtered at build time using Go [build constraints].

static

Controls whether a binary is statically linked. May be one of on, off, or auto. Not available on all platforms or in all modes. It's usually better to control this on the command line with --@io_bazel_rules_go//go/config:static. See [mode attributes], specifically [static].

x_defs

Map of defines to add to the go link command. See [Defines and stamping] for examples of how to use these.


go_library

This builds a Go library from a set of source files that are all part of the same package.

Note: For targets generated by Gazelle, name is typically the last component of the path, or go_default_library, with the old naming convention.

Providers:

  • [GoLibrary]
  • [GoSource]
  • [GoArchive]

name

A unique name for this target.

cdeps

List of other libraries that the c code depends on. This can be anything that would be allowed in [cc_library deps] Only valid if cgo = True.

cgo

If True, the package may contain [cgo] code, and srcs may contain C, C++, Objective-C, and Objective-C++ files and non-Go assembly files. When cgo is enabled, these files will be compiled with the C/C++ toolchain and included in the package. Note that this attribute does not force cgo to be enabled. Cgo is enabled for non-cross-compiling builds when a C/C++ toolchain is configured.

clinkopts

List of flags to add to the C link command. Subject to ["Make variable"] substitution and [Bourne shell tokenization]. Only valid if cgo = True.

copts

List of flags to add to the C compilation command. Subject to ["Make variable"] substitution and [Bourne shell tokenization]. Only valid if cgo = True.

cppopts

List of flags to add to the C/C++ preprocessor command. Subject to ["Make variable"] substitution and [Bourne shell tokenization]. Only valid if cgo = True.

cxxopts

List of flags to add to the C++ compilation command. Subject to ["Make variable"] substitution and [Bourne shell tokenization]. Only valid if cgo = True.

data

List of files needed by this rule at run-time. This may include data files needed or other programs that may be executed. The [bazel] package may be used to locate run files; they may appear in different places depending on the operating system and environment. See [data dependencies] for more information on data files.

deps

List of Go libraries this package imports directly. These may be go_library rules or compatible rules with the [GoLibrary] provider.

embed

List of Go libraries whose sources should be compiled together with this package's sources. Labels listed here must name go_library, go_proto_library, or other compatible targets with the [GoLibrary] and [GoSource] providers. Embedded libraries must have the same importpath as the embedding library. At most one embedded library may have cgo = True, and the embedding library may not also have cgo = True. See [Embedding] for more information.

embedsrcs

The list of files that may be embedded into the compiled package using //go:embed directives. All files must be in the same logical directory or a subdirectory as source files. All source files containing //go:embed directives must be in the same logical directory. It's okay to mix static and generated source files and static and generated embeddable files.

gc_goopts

List of flags to add to the Go compilation command when using the gc compiler. Subject to ["Make variable"] substitution and [Bourne shell tokenization].

importmap

The actual import path of this library. By default, this is importpath. This is mostly only visible to the compiler and linker, but it may also be seen in stack traces. This must be unique among packages passed to the linker. It may be set to something different than importpath to prevent conflicts between multiple packages with the same path (for example, from different vendor directories).

importpath

The source import path of this library. Other libraries can import this library using this path. This must either be specified in go_library or inherited from one of the libraries in embed.

importpath_aliases

srcs

The list of Go source files that are compiled to create the package. Only .go and .s files are permitted, unless the cgo attribute is set, in which case, .c .cc .cpp .cxx .h .hh .hpp .hxx .inc .m .mm files are also permitted. Files may be filtered at build time using Go [build constraints].

x_defs

Map of defines to add to the go link command. See [Defines and stamping] for examples of how to use these.


go_path

go_path builds a directory structure that can be used with tools that understand the GOPATH directory layout. This directory structure can be built by zipping, copying, or linking files. go_path can depend on one or more Go targets (i.e., [go_library], [go_binary], or [go_test]). It will include packages from those targets, as well as their transitive dependencies. Packages will be in subdirectories named after their importpath or importmap attributes under a src/ directory.

name

A unique name for this target.

data

A list of targets producing data files that will be stored next to the src/ directory. Useful for including things like licenses and readmes.

deps

A list of targets that build Go packages. A directory will be generated from files in these targets and their transitive dependencies. All targets must provide [GoArchive] ([go_library], [go_binary], [go_test], and similar rules have this).

Only targets with explicit importpath attributes will be included in the generated directory. Synthetic packages (like the main package produced by [go_test]) and packages with inferred import paths will not be included. The values of importmap attributes may influence the placement of packages within the generated directory (for example, in vendor directories).

The generated directory will contain original source files, including .go, .s, .h, and .c files compiled by cgo. It will not contain files generated by tools like cover and cgo, but it will contain generated files passed in srcs attributes like .pb.go files. The generated directory will also contain runfiles found in data attributes.

include_data

When true, data files referenced by libraries, binaries, and tests will be included in the output directory. Files listed in the data attribute for this rule will be included regardless of this attribute.

include_pkg

When true, a pkg subdirectory containing the compiled libraries will be created in the generated GOPATH containing compiled libraries.

include_transitive

When true, the transitive dependency graph will be included in the generated GOPATH. This is the default behaviour. When false, only the direct dependencies will be included in the generated GOPATH.

mode

Determines how the generated directory is provided. May be one of:

  • "archive": The generated directory is packaged as a single .zip file.
  • "copy": The generated directory is a single tree artifact. Source files are copied into the tree.
  • "link": Source files are symlinked into the tree. All of the symlink files are provided as separate output files.

Note: In "copy" mode, when a GoPath is consumed as a set of input files or run files, Bazel may provide symbolic links instead of regular files. Any program that consumes these files should dereference links, e.g., if you run tar, use the --dereference flag.


go_source

This declares a set of source files and related dependencies that can be embedded into one of the other rules. This is used as a way of easily declaring a common set of sources re-used in multiple rules.

Providers:

  • [GoLibrary]
  • [GoSource]

name

A unique name for this target.

data

List of files needed by this rule at run-time. This may include data files needed or other programs that may be executed. The [bazel] package may be used to locate run files; they may appear in different places depending on the operating system and environment. See [data dependencies] for more information on data files.

deps

List of Go libraries this source list imports directly. These may be go_library rules or compatible rules with the [GoLibrary] provider.

embed

List of Go libraries whose sources should be compiled together with this package's sources. Labels listed here must name go_library, go_proto_library, or other compatible targets with the [GoLibrary] and [GoSource] providers. Embedded libraries must have the same importpath as the embedding library. At most one embedded library may have cgo = True, and the embedding library may not also have cgo = True. See [Embedding] for more information.

gc_goopts

List of flags to add to the Go compilation command when using the gc compiler. Subject to ["Make variable"] substitution and [Bourne shell tokenization].

srcs

The list of Go source files that are compiled to create the package. The following file types are permitted: .go, .c, .s, .S .h. The files may contain Go-style [build constraints].


go_test

This builds a set of tests that can be run with bazel test.

To run all tests in the workspace, and print output on failure (the equivalent of go test ./...), run

bazel test --test_output=errors //...
```<br><br>
To run a Go benchmark test, run<br>

bazel run //path/to:test -- -test.bench=.

You can run specific tests by passing the `--test_filter=pattern
<test_filter_>` argument to Bazel. You can pass arguments to tests by passing
`--test_arg=arg <test_arg_>` arguments to Bazel, and you can set environment
variables in the test environment by passing
`--test_env=VAR=value <test_env_>`.<br><br>
To write structured testlog information to Bazel's `XML_OUTPUT_FILE`, tests
ran with `bazel test` execute using a wrapper. This functionality can be
disabled by setting `GO_TEST_WRAP=0` in the test environment. Additionally,
the testbinary can be invoked with `-test.v` by setting
`GO_TEST_WRAP_TESTV=1` in the test environment; this will result in the
`XML_OUTPUT_FILE` containing more granular data.<br><br>
***Note:*** To interoperate cleanly with old targets generated by [Gazelle], `name`
should be `go_default_test` for internal tests and
`go_default_xtest` for external tests. Gazelle now generates
the name  based on the last component of the path. For example, a test
in `//foo/bar` is named `bar_test`, and uses internal and external
sources.

name

A unique name for this target.

cdeps

The list of other libraries that the c code depends on. This can be anything that would be allowed in [cc_library deps] Only valid if cgo = True.

cgo

If True, the package may contain [cgo] code, and srcs may contain C, C++, Objective-C, and Objective-C++ files and non-Go assembly files. When cgo is enabled, these files will be compiled with the C/C++ toolchain and included in the package. Note that this attribute does not force cgo to be enabled. Cgo is enabled for non-cross-compiling builds when a C/C++ toolchain is configured.

clinkopts

List of flags to add to the C link command. Subject to ["Make variable"] substitution and [Bourne shell tokenization]. Only valid if cgo = True.

copts

List of flags to add to the C compilation command. Subject to ["Make variable"] substitution and [Bourne shell tokenization]. Only valid if cgo = True.

cppopts

List of flags to add to the C/C++ preprocessor command. Subject to ["Make variable"] substitution and [Bourne shell tokenization]. Only valid if cgo = True.

cxxopts

List of flags to add to the C++ compilation command. Subject to ["Make variable"] substitution and [Bourne shell tokenization]. Only valid if cgo = True.

data

List of files needed by this rule at run-time. This may include data files needed or other programs that may be executed. The [bazel] package may be used to locate run files; they may appear in different places depending on the operating system and environment. See [data dependencies] for more information on data files.

deps

List of Go libraries this test imports directly. These may be go_library rules or compatible rules with the [GoLibrary] provider.

embed

List of Go libraries whose sources should be compiled together with this package's sources. Labels listed here must name go_library, go_proto_library, or other compatible targets with the [GoLibrary] and [GoSource] providers. Embedded libraries must have the same importpath as the embedding library. At most one embedded library may have cgo = True, and the embedding library may not also have cgo = True. See [Embedding] for more information.

embedsrcs

The list of files that may be embedded into the compiled package using //go:embed directives. All files must be in the same logical directory or a subdirectory as source files. All source files containing //go:embed directives must be in the same logical directory. It's okay to mix static and generated source files and static and generated embeddable files.

env

Environment variables to set for the test execution. The values (but not keys) are subject to location expansion but not full make variable expansion.

gc_goopts

List of flags to add to the Go compilation command when using the gc compiler. Subject to ["Make variable"] substitution and [Bourne shell tokenization].

gc_linkopts

List of flags to add to the Go link command when using the gc compiler. Subject to ["Make variable"] substitution and [Bourne shell tokenization].

goarch

Forces a binary to be cross-compiled for a specific architecture. It's usually better to control this on the command line with --platforms.

This disables cgo by default, since a cross-compiling C/C++ toolchain is rarely available. To force cgo, set pure = off.

See [Cross compilation] for more information.

goos

Forces a binary to be cross-compiled for a specific operating system. It's usually better to control this on the command line with --platforms.

This disables cgo by default, since a cross-compiling C/C++ toolchain is rarely available. To force cgo, set pure = off.

See [Cross compilation] for more information.

gotags

Enables a list of build tags when evaluating [build constraints]. Useful for conditional compilation.

importpath

The import path of this test. Tests can't actually be imported, but this may be used by [go_path] and other tools to report the location of source files. This may be inferred from embedded libraries.

linkmode

Determines how the binary should be built and linked. This accepts some of the same values as go build -buildmode and works the same way.

  • `normal`: Builds a normal executable with position-dependent code.
  • `pie`: Builds a position-independent executable.
  • `plugin`: Builds a shared library that can be loaded as a Go plugin. Only supported on platforms that support plugins.
  • `c-shared`: Builds a shared library that can be linked into a C program.
  • `c-archive`: Builds an archive that can be linked into a C program.

msan

Controls whether code is instrumented for memory sanitization. May be one of on, on, or auto. Not available when cgo is disabled. In most cases, it's better to control this on the command line with --@io_bazel_rules_go//go/config:msan. See [mode attributes], specifically [msan].

pure

Controls whether cgo source code and dependencies are compiled and linked, similar to setting CGO_ENABLED. May be one of on, off, or auto. If auto, pure mode is enabled when no C/C++ toolchain is configured or when cross-compiling. It's usually better to control this on the command line with --@io_bazel_rules_go//go/config:pure. See [mode attributes], specifically [pure].

race

Controls whether code is instrumented for race detection. May be one of on, on, or auto. Not available when cgo is disabled. In most cases, it's better to control this on the command line with --@io_bazel_rules_go//go/config:race. See [mode attributes], specifically [race].

rundir

A directory to cd to before the test is run. This should be a path relative to the execution dir of the test.

       The default behaviour is to change to the workspace relative path, this replicates the normal
       behaviour of `go test` so it is easy to write compatible tests.

       Setting it to `.` makes the test behave the normal way for a bazel test.

       ***Note:*** This defaults to the package path.

srcs

The list of Go source files that are compiled to create the package. Only .go and .s files are permitted, unless the cgo attribute is set, in which case, .c .cc .cpp .cxx .h .hh .hpp .hxx .inc .m .mm files are also permitted. Files may be filtered at build time using Go [build constraints].

static

Controls whether a binary is statically linked. May be one of on, off, or auto. Not available on all platforms or in all modes. It's usually better to control this on the command line with --@io_bazel_rules_go//go/config:static. See [mode attributes], specifically [static].

x_defs

Map of defines to add to the go link command. See [Defines and stamping] for examples of how to use these.