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
See the WORKSPACE setup section for the current release.
If you want to use
lib/unittest.bzl from Skylib versions released in or after
December 2018, then you also should add to the
load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace") bazel_skylib_workspace()
Then, in the
*.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/)
- sets - deprecated, use
List of rules (in rules/)
Writing a new module
Steps to add a module to Skylib:
Create a new
.bzlfile in the
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
thingsand had a function named
things.bzlfile would look like this:
def _manipulate(): ... things = struct( manipulate=_manipulate, )
Add unit tests for your module in the
bzl_library.bzl rule can be used to aggregate a set of
Starlark files and its dependencies for use in test targets and
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