Release 0.12.0: modernize toolchain and CI matrix

[justinhoward]

Why

Master's last green CI run was July 2025. Since then, GitHub Actions runner upgrades and dependency drift made the workflow effectively unrunnable: OpenSearch service containers fail to boot, simplecov-cobertura 2.1.0 produces a coverage report the new REXML parser rejects (so even passing test runs exit 1), and the Rubocop pin is two years stale. This blocked any PR (e.g. #70) from getting a clean signal.

The codebase has been functionally stable for a while, so rather than patching individual pins this branch modernizes the floor and ships the result as 0.12.0. Runtime behavior is unchanged from 0.11.0 — the version bump reflects the support-policy and toolchain breaking changes only (per the 0.x convention of bumping the minor on breaking changes). Upgrading should be a drop-in replacement on any supported Ruby.

What's in here

0.12.0 release prep

• lib/faulty/version.rb -> 0.12.0.
• CHANGELOG.md gets a [0.12.0] section with Breaking / Changed / Removed buckets calling out the Ruby support drop.
• faulty.gemspec declares required_ruby_version = '>= 3.1', so older Rubies refuse to install the gem.

Runtime

• Drop support for Ruby < 3.1 (2.3 - 3.0 are EOL upstream).
• Lazy-require 'logger' in LogListener#initialize only when the fallback ::Logger.new($stderr) branch is actually taken. Ruby 3.5 extracts logger from default gems, and the eager require crashed boot with NameError on stock 3.3+. Pre-existing bug, surfaced once transitive requires went away.

CI matrix (.github/workflows/ci.yml)

• Ruby: 3.1, 3.2, 3.3, 3.4, jruby-head, truffleruby-head.
• OpenSearch: 2.19.5 default + a 3.0.0 row. Pass DISABLE_INSTALL_DEMO_CONFIG=true to the service container so OpenSearch 2.12+ doesn't refuse to boot waiting on OPENSEARCH_INITIAL_ADMIN_PASSWORD for a security demo we're immediately disabling anyway.
• Elasticsearch: keep the 7.17.x back-compat row. Image is bumped to elasticsearch:7.17.28 (the JDK in the original 7.17.0 image NPEs against the cgroupv2 setup on current runners); gem floor is elasticsearch ~> 7.17.11, the latest 7.17 client. Drop the Elasticsearch 8.15.0 row entirely — the Faulty patch still references Elasticsearch::Transport::Transport::Error, and ES 8+ moved transport into the elastic-transport gem under Elastic::Transport. ES 8 support is a separate refactor, tracked as follow-up.
• Redis: default redis gem 5, keep one 4 row, drop 3.
• Actions: checkout@v4, codecov-action@v5. Toolchain jobs (rubocop / yard / check_version / release) move to Ruby 3.4.

Gemfile

• Replace deprecated :mingw / :x64_mingw platform symbols with the unified :windows symbol Bundler now expects (the old form prints a [DEPRECATED] line at every bundle install).
• Pin rubocop ~> 1.84 (was 1.32; the old version emitted a wall of deprecation warnings against rubocop-ast 1.49).
• Pin rubocop-rspec ~> 3.9.
• Pin simplecov-cobertura ~> 3.1 (the 2.x XML-without-root-element bug is fixed in 3.x).
• Pin opensearch-ruby ~> 3.4 (was 2.1).
• Add logger for dev/test/benchmark only.

Rubocop config

• TargetRubyVersion: 3.1, NewCops: enable, migrate require: to plugins:.
• Drop the now-extracted RSpec/Capybara/*, RSpec/Rails/*, RSpec/FactoryBot/* entries; replace RSpec/FilePath with the new RSpec/SpecFilePath{Format,Suffix} knobs.
• Scope-exclude three new cops that misfire on intentional patterns: Naming/PredicateMethod (lib/faulty/storage/** - open/close/reopen are imperative interface methods that happen to return booleans; renaming would break Storage::Interface), Style/OneClassPerFile (lib/faulty/patch/** - monkey-patches reopen upstream constants), and RSpec/IndexedLet (auto_wire_spec.rb - numbered duplicate-backend fixtures read clearer than contrived names).
• Disable Gemspec/DevelopmentDependencies (the gemspec intentionally splits essential vs non-essential dev deps with the Gemfile).

Autocorrects from rubocop -A (no behavior change)

• &block -> anonymous & forwarding.
• begin/rescue/end inside a method body -> method/block-level rescue.
• ::Redis / ::Logger -> Redis / Logger (no namespace collisions).
• **hash.merge(k: v) -> hash, k: v.
• .select { |k,_v| %i[..].include?(k) } -> .slice(...).
• add_runtime_dependency -> add_dependency.

Tiny spec touch-ups

• Wrap three "nothing raises" tests in expect { ... }.not_to raise_error so they actually assert behavior (and silence RSpec/NoExpectationExample).
• Drop the Ruby-2.3 mysql2 carve-out in spec_helper.rb.

Test plan

• bundle exec rubocop - 81 files, 0 offenses.
• bin/yardoc --fail-on-warning - 87% documented, no warnings.
• bin/benchmark runs cleanly on this branch. Two-run averages show the in-memory / log-listener paths land ~2 - 3% faster than master (consistent direction across all four CPU-bound rows, plausibly from .slice and anonymous-block forwarding); Redis paths are within run-to-run noise.
• Full matrix green on push.

Follow-up

• PR Reserve half-open tests #70 ("Reserve half-open tests") still has a real Metrics/AbcSize offense in the new pipelined Redis#status. Easiest fix once this branch lands and Reserve half-open tests #70 rebases on top: extract the futures-fetch into a small helper. Not in scope here.
• Elasticsearch 8.x client support. Requires reworking lib/faulty/patch/elasticsearch.rb to handle both the pre-8 Elasticsearch::Transport namespace and the 8.x Elastic::Transport namespace (in the split-out elastic-transport gem). Tracked separately so it doesn't gate this release.