bazel-lib/README.md

Aspect's Bazel helpers library

Base Starlark libraries and basic Bazel rules which are useful for constructing rulesets and BUILD files.

This module depends on bazel-skylib. In theory all these utilities could be upstreamed to bazel-skylib, but the declared scope of that project is narrow and it's very difficult to get anyone's attention to review PRs there.

bazel-lib is just a part of what Aspect provides:

• Need help? This ruleset has support provided by https://aspect.dev.
• See our other Bazel rules: https://github.com/aspect-build

Installation

Installation instructions are included on each release: https://github.com/aspect-build/bazel-lib/releases

To use a commit rather than a release, you can point at any SHA of the repo.

For example to use commit abc123:

1. Replace url = "https://github.com/aspect-build/bazel-lib/releases/download/v0.1.0/bazel-lib-v0.1.0.tar.gz" with a GitHub-provided source archive like url = "https://github.com/aspect-build/bazel-lib/archive/abc123.tar.gz"
2. Replace strip_prefix = "bazel-lib-0.1.0" with strip_prefix = "bazel-lib-abc123"
3. Update the sha256. The easiest way to do this is to comment out the line, then Bazel will print a message with the correct value.

Note that GitHub source archives don't have a strong guarantee on the sha256 stability, see https://github.blog/2023-02-21-update-on-the-future-stability-of-source-code-archives-and-hashes

Public API

Copying files

• copy_directory Copies directories to another package.
• copy_file Copies files to another package.
• copy_to_bin Copies a source file to output tree at the same workspace-relative path.
• copy_to_directory Copies and arranges files and directories into a new directory.
• write_source_files Write to one or more files or folders in the source tree. Stamp out tests that ensure the sources exist and are up to date.

Transforming files

• jq A toolchain and custom rule for running jq, a tool that is "like sed for json".
• yq A toolchain and custom rule for running yq, a "YAML, JSON and XML processor".

Manipulating paths

• directory_path Provide a label to reference some path within a directory, via DirectoryPathInfo.
• output_files Forwards a subset of the files (via the DefaultInfo provider) from a given target's DefaultInfo or OutputGroupInfo.

Writing rules

• expand_make_vars Perform make variable and location substitutions in strings..
• expand_template Substitute templates with make variables, location resolves, stamp variables, and arbitrary strings.
• paths Useful path resolution methods.
• transitions Transition sources to a provided platform.
• lists Functional-style helpers for working with list data structures.
• utils Various utils for labels and globs.
• params_file Generate encoded params file from a list of arguments.
• repo_utils Useful methods for repository rule implementations.
• run_binary Like skylib's run_binary but adds directory output support.
• stamping Support version stamping in custom rules.
• base64 Starlark Base64 encoder & decoder.

Testing

• bats_test: A test runner for the Bash Automated Testing System.

Generating documentation

• docs Rules for generating docs and stamping tests to ensure they are up to date.