Bazel for Ruby (RubyKaigi 2025)

A talk about using Bazel in Ruby projects for RubyKaigi 2025 (https://rubykaigi.org/2025/presentations/p0deje.html).

Transcript

1. Bazel for Ruby
2. What is Bazel? How to use it with Ruby? What's done?
3. Alex Rodionov @p0deje Ruby maintainer @ Selenium Ruby maintainer @ Bazel Rules Authors SIG
4. What is Bazel? Build and test tool for monorepos Created at Google and open sourced Polyglot (Java, Python, Go, JavaScript, etc.) E ffi cient and scalable Hermetic and reproducible Distributed (remote caching and execution)
5. bazel build
6. bazel build
7. bazel test
8. It’s a graph!
9. It’s e ffi cient!
10. It’s hermetic!
11. It’s polyglot!
12. rules_java rules_python rules_nodejs rules_ts rules_go rules_rust rules_oci (Docker) rules_helm It’s polyglot!
13. Canonical Bazel ruleset supporting Ruby language Maintained by Bazel Rules Authors SIG Available in Bazel Central Registry Used by companies (Stripe, etc.) and open-source projects (Protobuf, Selenium, etc.) rules_ruby
14. Installs Ruby interpreter (CRuby, JRuby, Tru ff l eRuby) Installs dependencies via Bundler Provides rules for common operations: rb_library rb_binary rb_test rb_gem_build rb_gem_push rules_ruby
15. . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock │ │ ├─ lib │ │ │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
16. bazel_dep(name = "rules_ruby", version = "0.18.0") ruby = use_extension( "@rules_ruby // ruby:extensions.bzl", "ruby" ) ruby.toolchain( name = "ruby", version = "3.4.2", ) ruby.bundle_fetch( name = "bundle", gemfile = " //: Gemfile", gemfile_lock = " //: Gemfile.lock", ) use_repo(ruby, "bundle", "ruby", "ruby_toolchains") register_toolchains("@ruby_toolchains // :all") . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel │ ├─ lib │ │ │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
17. bazel_dep(name = "rules_ruby", version = "0.18.0") ruby = use_extension( "@rules_ruby // ruby:extensions.bzl", "ruby" ) ruby.toolchain( name = "ruby", version = "3.4.2", ) ruby.bundle_fetch( name = "bundle", gemfile = " //: Gemfile", gemfile_lock = " //: Gemfile.lock", ) use_repo(ruby, "bundle", "ruby", "ruby_toolchains") register_toolchains("@ruby_toolchains // :all") . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel │ ├─ lib │ │ │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
18. bazel_dep(name = "rules_ruby", version = "0.18.0") ruby = use_extension( "@rules_ruby // ruby:extensions.bzl", "ruby" ) ruby.toolchain( name = "ruby", version = "3.4.2", ) ruby.bundle_fetch( name = "bundle", gemfile = " //: Gemfile", gemfile_lock = " //: Gemfile.lock", ) use_repo(ruby, "bundle", "ruby", "ruby_toolchains") register_toolchains("@ruby_toolchains // :all") . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel │ ├─ lib │ │ │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
19. bazel_dep(name = "rules_ruby", version = "0.18.0") ruby = use_extension( "@rules_ruby // ruby:extensions.bzl", "ruby" ) ruby.toolchain( name = "ruby", version = "3.4.2", ) ruby.bundle_fetch( name = "bundle", gemfile = " //: Gemfile", gemfile_lock = " //: Gemfile.lock", ) use_repo(ruby, "bundle", "ruby", "ruby_toolchains") register_toolchains("@ruby_toolchains // :all") . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel │ ├─ lib │ │ │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
20. bazel_dep(name = "rules_ruby", version = "0.18.0") ruby = use_extension( "@rules_ruby // ruby:extensions.bzl", "ruby" ) ruby.toolchain( name = "ruby", version = "3.4.2", ) ruby.bundle_fetch( name = "bundle", gemfile = " //: Gemfile", gemfile_lock = " //: Gemfile.lock", ) use_repo(ruby, "bundle", "ruby", "ruby_toolchains") register_toolchains("@ruby_toolchains // :all") . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel │ ├─ lib │ │ │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
21. bazel_dep(name = "rules_ruby", version = "0.18.0") ruby = use_extension( "@rules_ruby // ruby:extensions.bzl", "ruby" ) ruby.toolchain( name = "ruby", version = "3.4.2", ) ruby.bundle_fetch( name = "bundle", gemfile = " //: Gemfile", gemfile_lock = " //: Gemfile.lock", ) use_repo(ruby, "bundle", "ruby", "ruby_toolchains") register_toolchains("@ruby_toolchains // :all") . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel │ ├─ lib │ │ │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
22. load( "@rules_ruby // ruby:defs.bzl", "rb_gem_build", ) rb_gem_build( name = "calendar", gemspec = "calendar.gemspec", deps = [" / / lib"], ) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ │ │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
23. load( "@rules_ruby // ruby:defs.bzl", "rb_gem_build", ) rb_gem_build( name = "calendar", gemspec = "calendar.gemspec", deps = [" / / lib"], ) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ │ │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
24. load( "@rules_ruby // ruby:defs.bzl", "rb_gem_build", ) rb_gem_build( name = "calendar", gemspec = "calendar.gemspec", deps = [" / / lib"], ) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ │ │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
25. $ bazel build // :calendar … ERROR : no such package 'lib': BUILD file not found in any of the following directories. Add a BUILD file to a directory to mark it as a package. … . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ │ │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
26. load("@rules_ruby // ruby:defs.bzl", "rb_library") rb_library( name = "lib", srcs = ["calendar.rb"], visibility = [" // visibility:public"], deps = [ " // lib/calendar:add", " // lib/calendar:remove", ], ) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
27. load("@rules_ruby // ruby:defs.bzl", "rb_library") rb_library( name = "lib", srcs = ["calendar.rb"], visibility = [" // visibility:public"], deps = [ " // lib/calendar:add", " // lib/calendar:remove", ], ) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
28. load("@rules_ruby // ruby:defs.bzl", "rb_library") rb_library( name = "lib", srcs = ["calendar.rb"], visibility = [" // visibility:public"], deps = [ " // lib/calendar:add", " // lib/calendar:remove", ], ) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ │ │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
29. load("@rules_ruby // ruby:defs.bzl", "rb_library") rb_library( name = "add", srcs = ["add.rb"], visibility = [" // visibility:public"], ) rb_library( name = "remove", srcs = ["remove.rb"], visibility = [" // visibility:public"], ) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ ├─ BUILD │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
30. $ bazel build // :calendar … INFO : From GemBuild calendar.gem: Successfully built RubyGem Name: calendar Version: 0.1.0 File: calendar-0.1.0.gem … bazel - bin/calendar.gem … . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ ├─ BUILD │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
31. load( "@rules_ruby // ruby:defs.bzl", "rb_gem_build", "rb_gem_push", ) rb_gem_build( name = "calendar", gemspec = "calendar.gemspec", deps = [" / / lib"], ) rb_gem_push( name = "calendar - release", gem = ":calendar", ) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ ├─ BUILD │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
32. $ bazel run // :calendar - release … Successfully built RubyGem Name: calendar Version: 0.1.0 File: calendar-0.1.0.gem … Pushing gem to https: // rubygems.org… Successfully registered gem: calendar (0.1.0) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ ├─ BUILD │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec │ ├─ add_spec.rb └─ remove_spec.rb
33. load("@rules_ruby // ruby:defs.bzl", "rb_test") rb_test( name = "add", srcs = ["add_spec.rb"], main = "@bundle // bin:rspec", deps = [ " // lib/gem:add", "@bundle", ], ) rb_test( name = "remove", srcs = ["remove_spec.rb"], main = "@bundle // bin:rspec", deps = [ " // lib/gem:remove", "@bundle", ], ) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ ├─ BUILD │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec ├─ BUILD ├─ add_spec.rb └─ remove_spec.rb
34. load("@rules_ruby // ruby:defs.bzl", "rb_test") rb_test( name = "add", srcs = ["add_spec.rb"], main = "@bundle // bin:rspec", deps = [ " // lib/gem:add", "@bundle", ], ) rb_test( name = "remove", srcs = ["remove_spec.rb"], main = "@bundle // bin:rspec", deps = [ " // lib/gem:remove", "@bundle", ], ) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ ├─ BUILD │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec ├─ BUILD ├─ add_spec.rb └─ remove_spec.rb
35. load("@rules_ruby // ruby:defs.bzl", "rb_test") rb_test( name = "add", srcs = ["add_spec.rb"], main = "@bundle // bin:rspec", deps = [ " // lib/gem:add", "@bundle", ], ) rb_test( name = "remove", srcs = ["remove_spec.rb"], main = "@bundle // bin:rspec", deps = [ " // lib/gem:remove", "@bundle", ], ) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ ├─ BUILD │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec ├─ BUILD ├─ add_spec.rb └─ remove_spec.rb
36. load("@rules_ruby // ruby:defs.bzl", "rb_test") rb_test( name = "add", srcs = ["add_spec.rb"], main = "@bundle // bin:rspec", deps = [ " // lib/gem:add", "@bundle", ], ) rb_test( name = "remove", srcs = ["remove_spec.rb"], main = "@bundle // bin:rspec", deps = [ " // lib/gem:remove", "@bundle", ], ) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ ├─ BUILD │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec ├─ BUILD ├─ add_spec.rb └─ remove_spec.rb
37. $ bazel test //. .. … // spec:add PASSED in 1.8s // spec:remove PASSED in 1.2s … . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ ├─ BUILD │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec ├─ BUILD ├─ add_spec.rb └─ remove_spec.rb
38. load( "@rules_ruby // ruby:defs.bzl", "rb_gem_build", "rb_gem_push", "rb_test", ) … rb_test( name = "rubocop", srcs = ["Gemfile"], main = "@bundle // bin:rubocop", deps = [ " // lib", " // spec:add", " // spec:remove", "@bundle", ], ) . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ ├─ BUILD │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec ├─ BUILD ├─ add_spec.rb └─ remove_spec.rb
39. $ bazel test //. .. … // spec:add (cached) PASSED in 1.8s // spec:remove (cached) PASSED in 1.2s // :rubocop PASSED in 3.5s … . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ ├─ BUILD │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec ├─ BUILD ├─ add_spec.rb └─ remove_spec.rb
40. $ bazel test //. .. … // spec:add (cached) PASSED in 1.8s // spec:remove (cached) PASSED in 1.2s // :rubocop PASSED in 3.5s … . ├─ calendar.gemspec ├─ Gemfile ├─ Gemfile.lock ├─ MODULE.bazel ├─ BUILD ├─ lib │ ├─ BUILD │ ├─ calendar │ │ ├─ BUILD │ │ ├─ add.rb │ │ └─ remove.rb │ └─ calendar.rb └─ spec ├─ BUILD ├─ add_spec.rb └─ remove_spec.rb
41. Parallel test execution (parallel_tests) Test regression selection (crystalball) Packages and visibility control (packwerk) Remote build and test caching Remote build and test execution (only JRuby) Please, CRuby team, make standalone prebuilt Ruby that doesn't require compiling! Compile C/Java programs with CRuby/JRuby Done in rules_ruby
42. Test sharding (knapsack) Test coverage (simplecov) Aspects (e.g. automatically typecheck during build) Better Gem fi le support (self-hosted RubyGems, gems from Git repositories) Better debugging support (rdbg) Todo in rules_ruby
43. Thank you! https://github.com/bazel-contrib/rules_ruby https://bazelbuild.slack.com/channels/ruby p0deje@gmail.com
44. Special thank you, 山 上!