README.md
Skylib
Skylib is a standard library that provides functions useful for manipulating collections, file paths, and other features that are useful when writing custom build rules in Bazel.
This library is currently under early development. Be aware that the APIs in these modules may change during this time.
Each of the .bzl
files in the lib
directory defines a "module"—a
struct
that contains a set of related functions and/or other symbols that can
be loaded as a single unit, for convenience.
Skylib also provides build rules under the rules
directory.
Getting Started
WORKSPACE
file
Add the following to your WORKSPACE
file to import the Skylib repository into
your workspace. Replace the version number in the tag
attribute with the
version you wish to depend on:
# bazel-skylib 0.8.0 released 2019.03.20 (https://github.com/bazelbuild/bazel-skylib/releases/tag/0.8.0)
skylib_version = "0.8.0"
http_archive(
name = "bazel_skylib",
type = "tar.gz",
url = "https://github.com/bazelbuild/bazel-skylib/releases/download/{}/bazel-skylib.{}.tar.gz".format (skylib_version, skylib_version),
sha256 = "2ef429f5d7ce7111263289644d233707dba35e39696377ebab8b0bc701f7818e",
)
If you want to use lib/unittest.bzl
from Skylib versions released in or after
December 2018, then you also should add to the WORKSPACE
file:
load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")
bazel_skylib_workspace()
BUILD
and *.bzl
files
Then, in the BUILD
and/or *.bzl
files in your own workspace, you can load
the modules (listed below) and access the symbols by
dotting into those structs:
load("@bazel_skylib//lib:paths.bzl", "paths")
load("@bazel_skylib//lib:shell.bzl", "shell")
p = paths.basename("foo.bar")
s = shell.quote(p)
List of modules (in lib/)
- collections
- dicts
- partial
- paths
- selects
- sets - deprecated, use
new_sets
- new_sets
- shell
- structs
- types
- unittest
- versions
List of rules (in rules/)
Writing a new module
Steps to add a module to Skylib:
-
Create a new
.bzl
file in thelib
directory. -
Write the functions or other symbols (such as constants) in that file, defining them privately (prefixed by an underscore).
-
Create the exported module struct, mapping the public names of the symbols to their implementations. For example, if your module was named
things
and had a function namedmanipulate
, yourthings.bzl
file would look like this:def _manipulate(): ... things = struct( manipulate=_manipulate, )
-
Add unit tests for your module in the
tests
directory.
bzl_library
The bzl_library.bzl
rule can be used to aggregate a set of
Starlark files and its dependencies for use in test targets and
documentation generation.
Troubleshooting
If you try to use unittest
and you get the following error:
ERROR: While resolving toolchains for target //foo:bar: no matching toolchains found for types @bazel_skylib//toolchains:toolchain_type
ERROR: Analysis of target '//foo:bar' failed; build aborted: no matching toolchains found for types @bazel_skylib//toolchains:toolchain_type
then you probably forgot to load and call bazel_skylib_workspace()
in your
WORKSPACE
file.