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Repository rules

Repository rules are Bazel rules that can be used in WORKSPACE files to import projects in external repositories. Repository rules may download projects and transform them by applying patches or generating build files.

The Gazelle repository provides three rules:

  • go_repository downloads a Go project using either go mod download, a version control tool like git, or a direct HTTP download. It understands Go import path redirection. If build files are not already present, it can generate them with Gazelle.
  • git_repository downloads a project with git. Unlike the native git_repository, this rule allows you to specify an "overlay": a set of files to be copied into the downloaded project. This may be used to add pre-generated build files to a project that doesn't have them.
  • http_archive downloads a project via HTTP. It also lets you specify overlay files.

NOTE: git_repository and http_archive are deprecated in favor of the rules of the same name in @bazel_tools//tools/build_defs/repo:git.bzl and @bazel_tools//tools/build_defs/repo:http.bzl.

Repository rules can be loaded and used in WORKSPACE like this:

load("@bazel_gazelle//:deps.bzl", "go_repository")

go_repository(
    name = "com_github_pkg_errors",
    commit = "816c9085562cd7ee03e7f8188a1cfd942858cded",
    importpath = "github.com/pkg/errors",
)

Gazelle can add and update some of these rules automatically using the update-repos command. For example, the rule above can be added with:

$ gazelle update-repos github.com/pkg/errors

go_repository

go_repository downloads a Go project and generates build files with Gazelle if they are not already present. This is the simplest way to depend on external Go projects.

When go_repository is in module mode, it saves downloaded modules in a shared, internal cache within Bazel's cache. It may be cleared with bazel clean --expunge. By setting the environment variable GO_REPOSITORY_USE_HOST_CACHE=1, you can force go_repository to use the module cache on the host system in the location returned by go env GOPATH.

Example

load("@bazel_gazelle//:deps.bzl", "go_repository")

# Download using "go mod download"
go_repository(
    name = "com_github_pkg_errors",
    importpath = "github.com/pkg/errors",
    sum = "h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=",
    version = "v0.8.1",
)

# Download automatically via git
go_repository(
    name = "com_github_pkg_errors",
    commit = "816c9085562cd7ee03e7f8188a1cfd942858cded",
    importpath = "github.com/pkg/errors",
)

# Download from git fork
go_repository(
    name = "com_github_pkg_errors",
    commit = "816c9085562cd7ee03e7f8188a1cfd942858cded",
    importpath = "github.com/pkg/errors",
    remote = "https://example.com/fork/github.com/pkg/errors",
    vcs = "git",
)

# Download via HTTP
go_repository(
    name = "com_github_pkg_errors",
    importpath = "github.com/pkg/errors",
    urls = ["https://codeload.github.com/pkg/errors/zip/816c9085562cd7ee03e7f8188a1cfd942858cded"],
    strip_prefix = "errors-816c9085562cd7ee03e7f8188a1cfd942858cded",
    type = "zip",
)

Attributes

Name Type Default value
name string mandatory value
A unique name for this rule. This should usually be the Java-package-style name of the URL, with underscores as separators, for example, com_github_example_project.
importpath string mandatory value

The Go import path that matches the root directory of this repository. In module mode (when version is set), this must be the module path. If neither urls nor remote is specified, go_repository will automatically find the true path of the module, applying import path redirection.

If build files are generated for this repository, libraries will have their importpath attributes prefixed with this importpath string.
version string ""
If specified, go_repository will download the module at this version using go mod download. sum must also be set. commit, tag, and urls may not be set.
sum string ""

A hash of the module contents. In module mode, go_repository will verify the downloaded module matches this sum. May only be set when version is also set.

A value for sum may be found in the go.sum file or by running go mod download -json <module>@<version>.
replace string ""

A replacement for the module named by importpath. The module named by replace will be downloaded at version and verified with sum.

NOTE: There is no go_repository equivalent to file path replace directives. Use local_repository instead.
commit string ""
If the repository is downloaded using a version control tool, this is the commit or revision to check out. With git, this would be a sha1 commit id. commit and tag may not both be set.
tag string ""
If the repository is downloaded using a version control tool, this is the named revision to check out. commit and tag may not both be set.
vcs string ""

One of "git", "hg", "svn", "bzr".

The version control system to use. This is usually determined automatically, but it may be necessary to set this when remote is set and the VCS cannot be inferred. You must have the corresponding tool installed on your host.
remote string ""
The VCS location where the repository should be downloaded from. This is usually inferred from importpath, but you can set remote to download from a private repository or a fork.
urls string list []
A list of HTTP(S) URLs where an archive containing the project can be downloaded. Bazel will attempt to download from the first URL; the others are mirrors.
strip_prefix string ""
If the repository is downloaded via HTTP (urls is set), this is a directory prefix to strip. See http_archive.strip_prefix.
type string ""

One of "zip", "tar.gz", "tgz", "tar.bz2", "tar.xz".

If the repository is downloaded via HTTP (urls is set), this is the file format of the repository archive. This is normally inferred from the downloaded file name.
sha256 string ""

If the repository is downloaded via HTTP (urls is set), this is the SHA-256 sum of the downloaded archive. When set, Bazel will verify the archive against this sum before extracting it.

CAUTION: Do not use this with services that prepare source archives on demand, such as codeload.github.com. Any minor change in the server software can cause differences in file order, alignment, and compression that break SHA-256 sums.
build_file_generation string "auto"

One of "auto", "on", "off".

Whether Gazelle should generate build files in the repository. In "auto" mode, Gazelle will run if there is no build file in the repository root directory.
build_config label @bazel_gazelle_go_repository_config//:WORKSPACE

A file that Gazelle should read to learn about external repositories before generating build files. This is useful for dependency resolution. For example, a go_repository rule in this file establishes a mapping between a repository name like golang.org/x/tools and a workspace name like org_golang_x_tools. Workspace directives like # gazelle:repository_macro are recognized.

go_repository rules will be re-evaluated when parts of WORKSPACE related to Gazelle's configuration are changed, including Gazelle directives and go_repository name and importpath attributes. Their content should still be fetched from a local cache, but build files will be regenerated. If this is not desirable, build_config may be set to a less frequently updated file or None to disable this functionality.
build_file_name string BUILD.bazel,BUILD
Comma-separated list of names Gazelle will consider to be build files. If a repository contains files named build that aren't related to Bazel, it may help to set this to "BUILD.bazel", especially on case-insensitive file systems.
build_external string ""

One of "external", "vendored".

This sets Gazelle's -external command line flag.

NOTE: This cannot be used to ignore the vendor directory in a repository. The -external flag only controls how Gazelle resolves imports which are not present in the repository. Use build_extra_args = ["-exclude=vendor"] instead.
build_tags string list []
This sets Gazelle's -build_tags command line flag.
build_file_proto_mode string ""

One of "default", "legacy", "disable", "disable_global" or "package".

This sets Gazelle's -proto command line flag. See Directives for more information on each mode.
build_extra_args string list []
A list of additional command line arguments to pass to Gazelle when generating build files.
build_directives string list []
A list of directives to be written to the root level build file before Calling Gazelle to generate build files. Each string in the list will be prefixed with # automatically. A common use case is to pass a list of Gazelle directives.
patches label list []
A list of patches to apply to the repository after gazelle runs.
patch_tool string "patch"
The patch tool used to apply patches.
patch_args string list ["-p0"]
Arguments passed to the patch tool when applying patches.
patch_cmds string list []
Commands to run in the repository after patches are applied.

git_repository

NOTE: git_repository is deprecated in favor of the rule of the same name in @bazel_tools//tools/build_defs/repo:git.bzl.

git_repository downloads a project with git. It has the same features as the native git_repository rule, but it also allows you to copy a set of files into the repository after download. This is particularly useful for placing pre-generated build files.

Example

load("@bazel_gazelle//:deps.bzl", "git_repository")

git_repository(
    name = "com_github_pkg_errors",
    remote = "https://github.com/pkg/errors",
    commit = "816c9085562cd7ee03e7f8188a1cfd942858cded",
    overlay = {
        "@my_repo//third_party:com_github_pkg_errors/BUILD.bazel.in" : "BUILD.bazel",
    },
)

Attributes

Name Type Default value
name string mandatory value
A unique name for this rule. This should usually be the Java-package-style name of the URL, with underscores as separators, for example, com_github_example_project.
remote string mandatory value
The remote repository to download.
commit string ""
The git commit to check out. Either commit or tag may be specified.
tag tag ""
The git tag to check out. Either commit or tag may be specified.
overlay dict {}

A set of files to copy into the downloaded repository. The keys in this dictionary are Bazel labels that point to the files to copy. These must be fully qualified labels (i.e., @repo//pkg:name) because relative labels are interpreted in the checked out repository, not the repository containing the WORKSPACE file. The values in this dictionary are root-relative paths where the overlay files should be written.

It's convenient to store the overlay dictionaries for all repositories in a separate .bzl file. See Gazelle's manifest.bzl for an example.

http_archive

NOTE: http_archive is deprecated in favor of the rule of the same name in @bazel_tools//tools/build_defs/repo:http.bzl.

http_archive downloads a project over HTTP(S). It has the same features as the native http_archive rule, but it also allows you to copy a set of files into the repository after download. This is particularly useful for placing pre-generated build files.

Example

load("@bazel_gazelle//:deps.bzl", "http_archive")

http_archive(
    name = "com_github_pkg_errors",
    urls = ["https://codeload.github.com/pkg/errors/zip/816c9085562cd7ee03e7f8188a1cfd942858cded"],
    strip_prefix = "errors-816c9085562cd7ee03e7f8188a1cfd942858cded",
    type = "zip",
    overlay = {
        "@my_repo//third_party:com_github_pkg_errors/BUILD.bazel.in" : "BUILD.bazel",
    },
)

Attributes

Name Type Default value
name string mandatory value
A unique name for this rule. This should usually be the Java-package-style name of the URL, with underscores as separators, for example, com_github_example_project.
urls string list mandatory value
A list of HTTP(S) URLs where the project can be downloaded. Bazel will attempt to download the first URL; the others are mirrors.
sha256 string ""

The SHA-256 sum of the downloaded archive. When set, Bazel will verify the archive against this sum before extracting it.

CAUTION: Do not use this with services that prepare source archives on demand, such as codeload.github.com. Any minor change in the server software can cause differences in file order, alignment, and compression that break SHA-256 sums.
strip_prefix string ""
A directory prefix to strip. See http_archive.strip_prefix.
type string ""

One of "zip", "tar.gz", "tgz", "tar.bz2", "tar.xz".

The file format of the repository archive. This is normally inferred from the downloaded file name.
overlay dict {}

A set of files to copy into the downloaded repository. The keys in this dictionary are Bazel labels that point to the files to copy. These must be fully qualified labels (i.e., @repo//pkg:name) because relative labels are interpreted in the checked out repository, not the repository containing the WORKSPACE file. The values in this dictionary are root-relative paths where the overlay files should be written.

It's convenient to store the overlay dictionaries for all repositories in a separate .bzl file. See Gazelle's manifest.bzl for an example.